Herschel observations of the Galactic HII region RCW 79

TL;DR

This study uses Herschel and archival data to analyze compact sources in the RCW 79 HII region, revealing properties of dense cores and their potential to form high-mass stars, emphasizing the role of density in core formation efficiency.

Contribution

First comprehensive multi-wavelength analysis of compact sources in RCW 79, linking core properties to star formation potential and density-dependent core formation efficiency.

Findings

50 compact sources identified with detailed physical parameters.

Detection of 12 candidate massive dense cores for high-mass star formation.

Core formation efficiency increases with density in dense condensations.

Abstract

Triggered star formation around HII regions could be an important process. The Galactic HII region RCW 79 is a prototypical object for triggered high-mass star formation. We take advantage of Herschel data from the surveys HOBYS, "Evolution of Interstellar Dust", and Hi-Gal to extract compact sources in this region, complemented with archival 2MASS, Spitzer, and WISE data to determine the physical parameters of the sources (e.g., envelope mass, dust temperature, and luminosity) by fitting the spectral energy distribution. We obtained a sample of 50 compact sources, 96% of which are situated in the ionization-compressed layer of cold and dense gas that is characterized by the column density PDF with a double-peaked lognormal distribution. The 50 sources have sizes of 0.1-0.4 pc with a typical value of 0.2 pc, temperatures of 11-26 K, envelope masses of 6-760 $M_\odot$, densities of 0.1-44 $\times$ $10^5$ cm$^{-3}$, and luminosities of 19-12712 $L_\odot$. The sources are classified into 16 class 0, 19 intermediate, and 15 class I objects. Their distribution follows the evolutionary tracks in the diagram of bolometric luminosity versus envelope mass (Lbol-Menv) well. A mass threshold of 140 $M_\odot$, determined from the Lbol-Menv diagram, yields 12 candidate massive dense cores that may form high-mass stars. The core formation efficiency (CFE) for the 8 massive condensations shows an increasing trend of the CFE with density. This suggests that the denser the condensation, the higher the fraction of its mass transformation into dense cores, as previously observed in other high-mass star-forming regions.

Tables

Table 1. Table 1: Herschel observational parameters

Instrument	Size	Time	ObsIDs	Date
	arcmin	s		yyyy-mm-dd
PACS	$30\times 30$	02768	1342188880, 1342188881	2010-01-03
SPIRE	$30\times 30$	0837	1342192054	2010-03-10

Table 2. Table 2: Derived parameters for the 50 compact sources

ID	$R.A.$	$Dec.$	$D_{\mathrm{dec}}^{\mathrm{eff}}$	$T_d$	$M_{\mathrm{env}}$	$n_{{}_{H_2}}^a$	$L_{\mathrm{bol}}$	$L_{\mathrm{smm}}/L_{\mathrm{bol}}$
	J2000	J2000	pc	K	$M_{\odot }$	${10}^5$ cm-3	$L_{\odot }$
1	13:40:57.312	-61:45:42.12	0.12	25.2 $\pm$ 0.5	173 $\pm$ 16	28.5 $\pm$ 2.6	7513 $\pm$ 1503	0.005
2	13:40:26.328	-61:47:54.6	0.12	20.5 $\pm$ 0.5	92 $\pm$ 11	15.1 $\pm$ 1.7	1411 $\pm$ 282	0.010
3	13:39:54.456	-61:41:09.24	0.16	24.4 $\pm$ 0.2	204 $\pm$ 9	13.1 $\pm$ 0.6	12712 $\pm$ 2542	0.003
4	13:40:26.448	-61:47:39.84	0.13	17.4 $\pm$ 0.6	162 $\pm$ 31	18.9 $\pm$ 3.6	781 $\pm$ 156	0.022
5	13:40:32.352	-61:47:20.04	0.16	21.8 $\pm$ 1.5	42 $\pm$ 15	3.0 $\pm$ 1.1	1411 $\pm$ 282	0.005
8	13:39:54.576	-61:40:59.52	0.12	18.1 $\pm$ 1.4	270 $\pm$ 106	44.4 $\pm$ 17.4	1607 $\pm$ 321	0.019
10	13:41:01.992	-61:44:14.28	0.12	23.1 $\pm$ 0.8	12 $\pm$ 2	2.0 $\pm$ 0.4	399 $\pm$ 80	0.006
11	13:40:09.168	-61:41:31.56	0.19	25.1 $\pm$ 0.3	39 $\pm$ 2	1.6 $\pm$ 0.1	3938 $\pm$ 788	0.002
15	13:39:49.560	-61:44:30.12	0.12	25.3 $\pm$ 1.0	10 $\pm$ 2	1.6 $\pm$ 0.3	240 $\pm$ 48	0.009
16	13:40:18.456	-61:47:07.44	0.19	17.6 $\pm$ 1.0	183 $\pm$ 53	7.4 $\pm$ 2.2	616 $\pm$ 123	0.032
19	13:40:37.704	-61:46:59.88	0.19	18.6 $\pm$ 1.7	87 $\pm$ 34	3.5 $\pm$ 1.4	456 $\pm$ 91	0.023
28	13:39:54.360	-61:42:59.4	0.19	20.8 $\pm$ 0.5	25 $\pm$ 3	1.0 $\pm$ 0.1	1215 $\pm$ 243	0.003
32	13:39:45.216	-61:44:41.64	0.16	25.5 $\pm$ 0.7	9 $\pm$ 1	0.6 $\pm$ 0.1	225 $\pm$ 45	0.009
33	13:40:36.648	-61:49:29.64	0.25	19.7 $\pm$ 0.2	55 $\pm$ 3	1.0 $\pm$ 0.1	340 $\pm$ 68	0.022
37	13:41:06.912	-61:45:54.72	0.18	17.1 $\pm$ 0.8	49 $\pm$ 13	2.2 $\pm$ 0.6	347 $\pm$ 69	0.014
42	13:40:27.240	-61:36:16.56	0.24	20.3 $\pm$ 0.8	54 $\pm$ 10	1.1 $\pm$ 0.2	392 $\pm$ 78	0.020
44	13:39:39.456	-61:43:31.08	0.19	23.4 $\pm$ 1.7	23 $\pm$ 8	0.9 $\pm$ 0.3	360 $\pm$ 72	0.012
45	13:40:29.424	-61:47:28.68	0.18	14.0 $\pm$ 0.6	360 $\pm$ 80	17.3 $\pm$ 3.8	290 $\pm$ 58	0.076
47	13:40:54.624	-61:46:40.08	0.20	17.0 $\pm$ 0.2	158 $\pm$ 10	5.3 $\pm$ 0.3	429 $\pm$ 86	0.036
49	13:40:46.584	-61:46:59.16	0.29	18.3 $\pm$ 6.4	31 $\pm$ 47	0.3 $\pm$ 0.5	128 $\pm$ 26	0.028
51	13:40:27.384	-61:47:48.48	0.12	15.8 $\pm$ 0.3	121 $\pm$ 12	19.8 $\pm$ 2.0	290 $\pm$ 58	0.035
58	13:39:58.704	-61:39:56.16	0.19	22.3 $\pm$ 0.6	14 $\pm$ 2	0.6 $\pm$ 0.1	167 $\pm$ 33	0.014
61	13:40:25.704	-61:32:23.28	0.21	10.9 $\pm$ 1.1	759 $\pm$ 384	22.4 $\pm$ 11.3	100 $\pm$ 20	0.234
69	13:39:55.704	-61:46:19.56	0.20	19.9 $\pm$ 0.7	32 $\pm$ 5	1.1 $\pm$ 0.2	206 $\pm$ 41	0.021
72	13:39:38.280	-61:43:06.24	0.19	24.1 $\pm$ 0.7	17 $\pm$ 2	0.7 $\pm$ 0.1	310 $\pm$ 62	0.011
85	13:41:03.144	-61:45:22.68	0.12	14.9 $\pm$ 0.9	150 $\pm$ 47	24.7 $\pm$ 7.7	188 $\pm$ 38	0.058
86	13:40:32.424	-61:42:35.64	0.17	22.4 $\pm$ 0.6	7 $\pm$ 1	0.4 $\pm$ 0.1	85 $\pm$ 17	0.014
89	13:40:04.032	-61:40:32.16	0.25	22.9 $\pm$ 0.7	14 $\pm$ 2	0.3 $\pm$ 0.1	201 $\pm$ 40	0.013
90	13:40:11.520	-61:42:24.84	0.19	17.6 $\pm$ 0.2	75 $\pm$ 4	3.0 $\pm$ 0.2	253 $\pm$ 51	0.032
92	13:41:48.648	-61:35:20.04	0.19	16.3 $\pm$ 0.8	37 $\pm$ 9	1.5 $\pm$ 0.4	80 $\pm$ 16	0.042
111	13:39:46.512	-61:38:54.6	0.13	19.0 $\pm$ 1.0	11 $\pm$ 3	1.3 $\pm$ 0.3	57 $\pm$ 11	0.025
115	13:40:21.192	-61:52:23.88	0.18	19.7 $\pm$ 0.7	6 $\pm$ 1	0.3 $\pm$ 0.1	40 $\pm$ 8	0.022
132	13:40:56.856	-61:37:43.32	0.12	18.2 $\pm$ 2.5	10 $\pm$ 6	1.5 $\pm$ 0.9	40 $\pm$ 8	0.029
141	13:40:59.328	-61:47:01.68	0.37	19.8 $\pm$ 0.7	28 $\pm$ 5	0.1 $\pm$ 0.1	178 $\pm$ 36	0.022
154	13:40:58.512	-61:48:45	0.25	21.1 $\pm$ 0.4	19 $\pm$ 2	0.3 $\pm$ 0.1	177 $\pm$ 35	0.017
161	13:41:07.176	-61:47:51.72	0.29	20.0 $\pm$ 0.2	23 $\pm$ 1	0.3 $\pm$ 0.1	157 $\pm$ 31	0.021
263	13:39:44.208	-61:41:29.76	0.26	15.5 $\pm$ 2.0	210 $\pm$ 96	3.4 $\pm$ 1.5	339 $\pm$ 68	0.050
265	13:41:10.248	-61:44:02.4	0.24	16.3 $\pm$ 0.6	54 $\pm$ 9	1.0 $\pm$ 0.2	117 $\pm$ 23	0.042
268	13:40:37.392	-61:51:28.8	0.19	15.2 $\pm$ 0.5	63 $\pm$ 10	2.6 $\pm$ 0.4	88 $\pm$ 18	0.055
270	13:40:28.680	-61:35:17.52	0.40	14.8 $\pm$ 1.2	225 $\pm$ 67	0.9 $\pm$ 0.3	263 $\pm$ 53	0.061
271	13:41:54.888	-61:35:09.96	0.36	20.4 $\pm$ 0.2	30 $\pm$ 2	0.2 $\pm$ 0.1	231 $\pm$ 46	0.019
272	13:39:50.760	-61:41:03.12	0.19	13.6 $\pm$ 2.4	353 $\pm$ 243	14.3 $\pm$ 9.8	238 $\pm$ 48	0.085
273	13:39:47.352	-61:39:47.16	0.19	23.1 $\pm$ 0.5	11 $\pm$ 1	0.5 $\pm$ 0.1	164 $\pm$ 33	0.013
274	13:39:39.384	-61:39:52.56	0.19	14.0 $\pm$ 1.0	42 $\pm$ 15	1.7 $\pm$ 0.6	34 $\pm$ 7	0.075
278	13:39:33.936	-61:40:55.2	0.12	14.2 $\pm$ 0.8	22 $\pm$ 6	3.6 $\pm$ 1.1	19 $\pm$ 4	0.072
280	13:40:16.608	-61:33:24.48	0.29	15.8 $\pm$ 1.8	75 $\pm$ 30	0.8 $\pm$ 0.3	131 $\pm$ 26	0.047
281	13:40:57.192	-61:49:52.32	0.20	21.2 $\pm$ 0.1	8 $\pm$ 0	0.3 $\pm$ 0.1	178 $\pm$ 36	0.007
291	13:41:03.096	-61:48:30.96	0.26	12.2 $\pm$ 0.1	103 $\pm$ 6	1.5 $\pm$ 0.1	32 $\pm$ 6	0.139
298	13:39:42.312	-61:40:26.76	0.19	19.5 $\pm$ 1.7	14 $\pm$ 6	0.6 $\pm$ 0.3	83 $\pm$ 17	0.023
316	13:41:00.360	-61:46:23.88	0.35	26.2 $\pm$ 0.1	34 $\pm$ 1	0.2 $\pm$ 0.1	1024 $\pm$ 205	0.008

Table 3. Table 3: Observed condensation parameters

Name	$R.A.$	$Dec.$	$R_{\mathrm{maj}}$	$R_{\min }$	$F_{870\mu m}$	$F_{870\mu m}^{Planck}$	$F_{1.2\mathrm{mm}}^a$	$\overline{T_d}$	$\overline{N_{H_2}}$	$\overline{N_{H_2}^{\mathrm{bg}}}$
	J2000	J2000	$″$	$″$	mJy	mJy	mJy	K	${10}^{22}$ cm-2	${10}^{22}$ cm-2
cond1	13:41:08.560	-61:44:17.43	25.9	38.2	514	1974	224	22	2.0	0.6
cond2	13:40:56.013	-61:46:21.92	105.2	72.1	8828	23240	4200	22	2.9	0.6
cond3	13:40:26.940	-61:47:27.88	122.6	64.5	7567	17833	2350	21	2.3	0.5
cond4	13:39:47.435	-61:41:17.14	90.2	47.6	6198	12585	3000	22	2.9	0.5
cond5	13:40:27.041	-61:35:42.84	26.8	58.8	1179	3088	795	20	2.1	0.7
cond6	13:40:08.717	-61:41:29.01	15.4	19.1	272	574	81	23	1.7	0.6
cond7	13:40:10.802	-61:42:24.84	20.5	17.1	281	665	144	21	2.0	0.5
cond8	13:40:25.868	-61:32:38.16	26.3	59.3	1088	3062	483	18	2.8	0.7

Table 4. Table 7: Original fluxes in the Herschel bands for the 50 compact sources

ID	$S_{p,70}$	$S_{70}$	$S_{p,100}$	$S_{100}$	$S_{p,160}$	$S_{160}$	$S_{p,250}$	$S_{250}$	$S_{p,350}$	$S_{350}$	$S_{p,500}$	$S_{500}$
	Jy ${\mathrm{beam}}^{-1}$	Jy	Jy ${\mathrm{beam}}^{-1}$	Jy	Jy ${\mathrm{beam}}^{-1}$	Jy	Jy ${\mathrm{beam}}^{-1}$	Jy	Jy ${\mathrm{beam}}^{-1}$	Jy	Jy ${\mathrm{beam}}^{-1}$	Jy
1	79.7 $\pm$ 1.6	149.6 $\pm$ 2.2	98.4 $\pm$ 2.2	227.8 $\pm$ 5.5	118.7 $\pm$ 3.0	188.1 $\pm$ 4.0	94.5 $\pm$ 4.4	92.3 $\pm$ 3.9	39.6 $\pm$ 2.4	38.3 $\pm$ 2.2	15.8 $\pm$ 1.0	19.4 $\pm$ 1.6
2	13.0 $\pm$ 0.3	23.2 $\pm$ 0.4	24.2 $\pm$ 0.3	32.7 $\pm$ 0.5	28.8 $\pm$ 1.2	42.0 $\pm$ 2.0	20.9 $\pm$ 0.6	25.2 $\pm$ 0.6	14.3 $\pm$ 1.0	14.6 $\pm$ 0.9	5.2 $\pm$ 0.6	5.8 $\pm$ 0.5
3	26.4 $\pm$ 0.9	95.8 $\pm$ 1.5	50.7 $\pm$ 0.3	303.2 $\pm$ 1.3	87.3 $\pm$ 2.6	199.9 $\pm$ 4.0	89.8 $\pm$ 1.1	96.6 $\pm$ 0.9	39.6 $\pm$ 1.4	40.0 $\pm$ 1.2	8.5 $\pm$ 1.0	8.2 $\pm$ 1.0
4	7.1 $\pm$ 0.6	10.4 $\pm$ 0.6	15.0 $\pm$ 0.5	17.9 $\pm$ 0.6	22.3 $\pm$ 1.3	32.6 $\pm$ 1.3	24.8 $\pm$ 0.6	28.3 $\pm$ 0.5	11.9 $\pm$ 1.0	12.0 $\pm$ 1.0	8.9 $\pm$ 0.6	9.3 $\pm$ 0.5
5	11.2 $\pm$ 0.5	20.6 $\pm$ 0.7	12.6 $\pm$ 0.6	20.7 $\pm$ 0.7	14.9 $\pm$ 1.1	29.8 $\pm$ 2.2	10.7 $\pm$ 0.9	10.4 $\pm$ 0.8	4.7 $\pm$ 1.2	6.1 $\pm$ 1.1	3.6 $\pm$ 0.8	3.6 $\pm$ 0.7
8	0.0 $\pm$ 1.2	0.4 $\pm$ 1.4	11.5 $\pm$ 2.2	47.8 $\pm$ 3.2	43.6 $\pm$ 2.9	58.1 $\pm$ 2.9	50.0 $\pm$ 0.9	55.1 $\pm$ 0.8	33.9 $\pm$ 1.3	35.4 $\pm$ 1.2	17.9 $\pm$ 1.1	18.3 $\pm$ 1.0
10	3.2 $\pm$ 0.2	5.6 $\pm$ 0.2	5.5 $\pm$ 0.3	9.3 $\pm$ 0.4	8.6 $\pm$ 0.9	10.1 $\pm$ 0.9	5.8 $\pm$ 1.2	4.2 $\pm$ 1.4	2.4 $\pm$ 1.2	2.1 $\pm$ 1.2	0.0 $\pm$ 0.4
11	5.0 $\pm$ 0.1	32.3 $\pm$ 0.2	7.0 $\pm$ 0.2	50.2 $\pm$ 0.5	17.1 $\pm$ 0.4	42.8 $\pm$ 0.6	16.5 $\pm$ 0.6	19.3 $\pm$ 0.6	8.9 $\pm$ 1.1	9.3 $\pm$ 1.2	3.1 $\pm$ 0.5	3.3 $\pm$ 1.3
15	3.4 $\pm$ 0.2	7.9 $\pm$ 0.2	5.8 $\pm$ 0.2	13.3 $\pm$ 0.3	8.6 $\pm$ 0.4	10.4 $\pm$ 0.4	6.8 $\pm$ 0.3	5.8 $\pm$ 0.3	2.9 $\pm$ 0.3	2.2 $\pm$ 0.3	1.4 $\pm$ 0.5	1.6 $\pm$ 0.4
16	3.4 $\pm$ 0.4	16.4 $\pm$ 0.7	4.3 $\pm$ 0.4	24.8 $\pm$ 0.8	16.3 $\pm$ 1.0	37.5 $\pm$ 1.2	25.6 $\pm$ 0.5	31.4 $\pm$ 0.4	14.7 $\pm$ 0.6	21.8 $\pm$ 1.3	7.5 $\pm$ 0.5	10.4 $\pm$ 0.7
19	2.7 $\pm$ 0.3	10.7 $\pm$ 0.4	4.3 $\pm$ 0.3	17.6 $\pm$ 0.5	12.2 $\pm$ 1.5	26.1 $\pm$ 1.9	14.6 $\pm$ 1.8	15.7 $\pm$ 1.6	10.1 $\pm$ 1.2	11.0 $\pm$ 1.1	5.2 $\pm$ 0.9	5.1 $\pm$ 0.8
28	1.1 $\pm$ 0.1	5.7 $\pm$ 0.1	2.1 $\pm$ 0.1	9.9 $\pm$ 0.2	5.6 $\pm$ 0.9	12.9 $\pm$ 1.1	6.8 $\pm$ 0.6	7.5 $\pm$ 0.6	2.9 $\pm$ 0.8	2.9 $\pm$ 0.7	1.9 $\pm$ 0.7	2.1 $\pm$ 0.6
32	2.1 $\pm$ 0.2	8.0 $\pm$ 0.3	3.4 $\pm$ 0.2	16.6 $\pm$ 0.4	5.5 $\pm$ 0.4	10.9 $\pm$ 0.4	3.8 $\pm$ 0.5	3.9 $\pm$ 0.4	1.8 $\pm$ 0.3	2.4 $\pm$ 0.4	1.7 $\pm$ 0.5	3.2 $\pm$ 0.6
33	0.8 $\pm$ 0.1	17.5 $\pm$ 0.4	1.5 $\pm$ 0.1	28.0 $\pm$ 0.5	6.2 $\pm$ 0.5	32.9 $\pm$ 1.1	7.9 $\pm$ 0.7	13.1 $\pm$ 0.8	5.2 $\pm$ 0.8	7.1 $\pm$ 0.8	2.6 $\pm$ 0.7	2.9 $\pm$ 0.6
37	0.6 $\pm$ 0.3	1.8 $\pm$ 0.4	1.3 $\pm$ 0.4	7.7 $\pm$ 0.9	5.5 $\pm$ 2.0	10.1 $\pm$ 2.9	8.3 $\pm$ 2.8	7.2 $\pm$ 2.4	3.0 $\pm$ 1.5	2.9 $\pm$ 1.6	1.0 $\pm$ 0.4	0.8 $\pm$ 0.3
42	1.6 $\pm$ 0.1	14.1 $\pm$ 0.2	3.1 $\pm$ 0.2	26.2 $\pm$ 0.6	10.1 $\pm$ 0.4	30.0 $\pm$ 1.1	9.6 $\pm$ 0.8	12.3 $\pm$ 0.8	7.3 $\pm$ 0.7	7.9 $\pm$ 0.6	3.2 $\pm$ 0.6	4.2 $\pm$ 1.0
44	2.0 $\pm$ 0.2	10.8 $\pm$ 0.4	2.9 $\pm$ 0.2	18.2 $\pm$ 0.7	6.6 $\pm$ 0.6	21.7 $\pm$ 1.0	4.8 $\pm$ 0.7	5.3 $\pm$ 0.7	3.3 $\pm$ 0.9	3.4 $\pm$ 0.9	1.5 $\pm$ 0.7	2.0 $\pm$ 0.6
45	0.6 $\pm$ 0.5	1.3 $\pm$ 0.6	1.6 $\pm$ 0.4	2.8 $\pm$ 0.5	11.3 $\pm$ 1.3	21.5 $\pm$ 1.3	22.4 $\pm$ 0.7	27.6 $\pm$ 0.6	15.4 $\pm$ 1.2	19.5 $\pm$ 1.1	9.2 $\pm$ 0.6	9.2 $\pm$ 0.6
47	2.6 $\pm$ 1.7	11.4 $\pm$ 2.8	5.4 $\pm$ 2.0	34.2 $\pm$ 3.8	12.7 $\pm$ 3.4	39.3 $\pm$ 4.7	18.6 $\pm$ 3.7	23.9 $\pm$ 3.4	11.1 $\pm$ 2.2	12.5 $\pm$ 2.0	9.6 $\pm$ 1.0	14.6 $\pm$ 0.9
49	0.0 $\pm$ 0.2	0.8 $\pm$ 0.3	0.5 $\pm$ 0.3	3.3 $\pm$ 0.5	5.2 $\pm$ 1.5	8.8 $\pm$ 1.8	7.1 $\pm$ 2.8	5.1 $\pm$ 2.5	4.8 $\pm$ 1.4	5.1 $\pm$ 1.3	4.7 $\pm$ 1.0	6.0 $\pm$ 0.9
51	0.8 $\pm$ 0.2	0.4 $\pm$ 0.2	5.0 $\pm$ 0.4	5.5 $\pm$ 0.4	11.8 $\pm$ 1.2	15.2 $\pm$ 1.2	14.1 $\pm$ 0.6	14.8 $\pm$ 0.6	7.3 $\pm$ 1.1	7.0 $\pm$ 1.0	3.9 $\pm$ 0.6	3.9 $\pm$ 0.5
58	1.4 $\pm$ 0.1	8.0 $\pm$ 0.1	2.1 $\pm$ 0.2	8.4 $\pm$ 0.4	4.0 $\pm$ 0.4	9.6 $\pm$ 0.6	3.9 $\pm$ 0.5	5.1 $\pm$ 0.4	1.4 $\pm$ 0.4	1.4 $\pm$ 0.7	1.5 $\pm$ 0.8	2.3 $\pm$ 0.7
61	0.1 $\pm$ 0.0	0.3 $\pm$ 0.1	0.3 $\pm$ 0.1	0.9 $\pm$ 0.1	2.9 $\pm$ 0.5	5.7 $\pm$ 0.6	10.3 $\pm$ 0.8	21.0 $\pm$ 1.6	9.3 $\pm$ 0.7	11.9 $\pm$ 0.7	6.9 $\pm$ 0.7	8.1 $\pm$ 0.7
69	1.4 $\pm$ 0.4	9.9 $\pm$ 0.9	1.9 $\pm$ 0.5	17.4 $\pm$ 1.1	5.3 $\pm$ 0.6	20.6 $\pm$ 0.8	6.3 $\pm$ 0.5	9.4 $\pm$ 0.5	3.8 $\pm$ 0.4	5.3 $\pm$ 0.4	1.9 $\pm$ 0.3	2.7 $\pm$ 0.3
72	1.7 $\pm$ 0.2	9.3 $\pm$ 0.3	2.0 $\pm$ 0.2	16.6 $\pm$ 0.5	5.5 $\pm$ 0.8	16.6 $\pm$ 1.1	4.5 $\pm$ 1.0	6.3 $\pm$ 0.9	2.5 $\pm$ 0.9	3.1 $\pm$ 0.8	0.8 $\pm$ 0.7	1.0 $\pm$ 0.6
85	0.1 $\pm$ 0.3	0.6 $\pm$ 0.4	0.9 $\pm$ 0.4	5.8 $\pm$ 0.9	7.3 $\pm$ 1.9	12.4 $\pm$ 2.7	14.2 $\pm$ 3.2	14.1 $\pm$ 2.8	8.5 $\pm$ 1.8	8.0 $\pm$ 1.6	5.0 $\pm$ 0.9	6.5 $\pm$ 1.0
86	0.4 $\pm$ 0.0	1.5 $\pm$ 0.1	0.6 $\pm$ 0.1	2.4 $\pm$ 0.1	2.7 $\pm$ 0.1	4.8 $\pm$ 0.1	2.5 $\pm$ 0.2	2.4 $\pm$ 0.1	1.3 $\pm$ 0.1	1.1 $\pm$ 0.1	0.5 $\pm$ 0.1	0.4 $\pm$ 0.1
89	1.3 $\pm$ 0.2	5.2 $\pm$ 0.5	1.7 $\pm$ 0.2	11.8 $\pm$ 0.5	4.1 $\pm$ 0.4	12.5 $\pm$ 0.6	3.6 $\pm$ 0.6	5.5 $\pm$ 0.6	2.5 $\pm$ 0.5	6.3 $\pm$ 0.9	2.5 $\pm$ 0.8	3.1 $\pm$ 0.7
90	0.2 $\pm$ 0.1	1.9 $\pm$ 0.1	1.0 $\pm$ 0.2	8.2 $\pm$ 0.5	5.7 $\pm$ 0.3	17.5 $\pm$ 0.5	10.9 $\pm$ 0.5	12.6 $\pm$ 0.6	6.6 $\pm$ 0.5	6.6 $\pm$ 0.5	2.9 $\pm$ 0.4	2.4 $\pm$ 0.7
92	0.1 $\pm$ 0.1	0.3 $\pm$ 0.1	0.2 $\pm$ 0.1	1.3 $\pm$ 0.2	2.1 $\pm$ 0.3	5.5 $\pm$ 0.5	3.6 $\pm$ 0.5	4.6 $\pm$ 0.4	2.2 $\pm$ 0.3	2.7 $\pm$ 0.3	1.5 $\pm$ 0.2	1.6 $\pm$ 0.2
111	0.4 $\pm$ 0.0	2.2 $\pm$ 0.1	0.8 $\pm$ 0.1	2.7 $\pm$ 0.1	2.3 $\pm$ 0.2	3.9 $\pm$ 0.3	2.2 $\pm$ 0.4	2.4 $\pm$ 0.3	1.4 $\pm$ 0.4	1.4 $\pm$ 0.4	0.6 $\pm$ 0.5	0.6 $\pm$ 0.4
115	0.3 $\pm$ 0.1	0.9 $\pm$ 0.1	0.6 $\pm$ 0.2	1.5 $\pm$ 0.3	1.6 $\pm$ 0.6	2.7 $\pm$ 0.6	1.9 $\pm$ 0.6	2.3 $\pm$ 0.5	0.8 $\pm$ 0.4	0.8 $\pm$ 0.4	0.3 $\pm$ 0.3	0.0 $\pm$ 0.3
132	0.1 $\pm$ 0.0	0.4 $\pm$ 0.0	0.6 $\pm$ 0.1	1.8 $\pm$ 0.1	1.8 $\pm$ 0.2	2.6 $\pm$ 0.2	2.1 $\pm$ 0.4	2.2 $\pm$ 0.4	1.3 $\pm$ 0.5	1.4 $\pm$ 0.4	0.5 $\pm$ 0.3	0.6 $\pm$ 0.2
141	0.3 $\pm$ 0.1	3.5 $\pm$ 0.2		8.0 $\pm$ 0.8		11.1 $\pm$ 2.2	0.2 $\pm$ 0.3	7.6 $\pm$ 0.8	0.2 $\pm$ 0.2	2.0 $\pm$ 0.2	0.0 $\pm$ 0.3	1.5 $\pm$ 0.2
154	0.9 $\pm$ 0.2	8.1 $\pm$ 0.4	1.3 $\pm$ 0.2	11.5 $\pm$ 0.5	3.5 $\pm$ 0.5	14.1 $\pm$ 0.9	3.9 $\pm$ 0.6	5.9 $\pm$ 0.6	2.1 $\pm$ 0.9	2.4 $\pm$ 0.8	1.0 $\pm$ 0.4	1.1 $\pm$ 0.4
161	0.5 $\pm$ 0.1	6.9 $\pm$ 0.3	0.8 $\pm$ 0.1	9.9 $\pm$ 0.3	2.6 $\pm$ 0.4	12.6 $\pm$ 0.8	3.2 $\pm$ 1.0	6.1 $\pm$ 1.0	1.6 $\pm$ 1.0	2.8 $\pm$ 0.9	0.8 $\pm$ 0.4	1.1 $\pm$ 0.3
263	0.3 $\pm$ 0.2	3.9 $\pm$ 0.7	0.5 $\pm$ 0.2	13.9 $\pm$ 1.0	3.3 $\pm$ 1.6	9.7 $\pm$ 2.8	15.6 $\pm$ 1.0	23.6 $\pm$ 1.4	9.9 $\pm$ 0.9	12.1 $\pm$ 1.1	7.7 $\pm$ 0.8	9.7 $\pm$ 0.7
265	0.0 $\pm$ 0.1	0.4 $\pm$ 0.1	0.1 $\pm$ 0.1	1.7 $\pm$ 0.4	3.5 $\pm$ 0.6	8.7 $\pm$ 0.9	5.9 $\pm$ 1.0	6.8 $\pm$ 0.9	4.5 $\pm$ 1.2	4.4 $\pm$ 1.1	2.5 $\pm$ 0.4	3.8 $\pm$ 0.4
268		2.0 $\pm$ 0.1	0.2 $\pm$ 0.1	3.0 $\pm$ 0.2	2.3 $\pm$ 0.4	6.1 $\pm$ 0.6	4.6 $\pm$ 0.5	6.8 $\pm$ 0.7	3.1 $\pm$ 0.5	3.4 $\pm$ 0.4	1.6 $\pm$ 0.4	1.3 $\pm$ 0.4
270	0.1 $\pm$ 0.0		0.3 $\pm$ 0.1	5.4 $\pm$ 0.3	2.9 $\pm$ 0.2	27.4 $\pm$ 0.6	7.6 $\pm$ 0.9	20.6 $\pm$ 1.5	6.0 $\pm$ 0.8	10.6 $\pm$ 1.0	4.5 $\pm$ 0.8	5.9 $\pm$ 0.8
271	0.6 $\pm$ 0.0	7.6 $\pm$ 0.2	0.9 $\pm$ 0.1	10.9 $\pm$ 0.2	2.8 $\pm$ 0.2	14.5 $\pm$ 0.5	3.2 $\pm$ 0.4	9.0 $\pm$ 0.5	2.0 $\pm$ 0.3	2.8 $\pm$ 0.3	1.2 $\pm$ 0.2	1.4 $\pm$ 0.2
272				4.4 $\pm$ 0.5	0.0 $\pm$ 1.2	0.0 $\pm$ 1.2	22.2 $\pm$ 1.2	23.3 $\pm$ 1.0	12.3 $\pm$ 1.2	12.9 $\pm$ 1.1	9.2 $\pm$ 0.9	8.9 $\pm$ 0.9
273	0.3 $\pm$ 0.2	3.9 $\pm$ 0.6	0.6 $\pm$ 0.2	8.8 $\pm$ 0.5	2.3 $\pm$ 0.4	8.6 $\pm$ 0.8	3.3 $\pm$ 0.4	4.9 $\pm$ 0.6	1.7 $\pm$ 0.7	1.8 $\pm$ 0.7	0.7 $\pm$ 0.4	0.7 $\pm$ 0.4
274	0.0 $\pm$ 0.0	1.4 $\pm$ 0.1	0.1 $\pm$ 0.0	1.3 $\pm$ 0.1	0.9 $\pm$ 0.2	2.3 $\pm$ 0.3	2.5 $\pm$ 0.4	3.3 $\pm$ 0.4	1.7 $\pm$ 0.4	1.6 $\pm$ 0.4	0.6 $\pm$ 0.4	0.2 $\pm$ 0.3
278	0.0 $\pm$ 0.1	0.0 $\pm$ 0.1	0.3 $\pm$ 0.1	0.5 $\pm$ 0.1	1.2 $\pm$ 0.4	1.3 $\pm$ 0.4	1.7 $\pm$ 0.6	1.7 $\pm$ 0.5	1.2 $\pm$ 0.6	2.1 $\pm$ 0.5	1.1 $\pm$ 0.4	1.1 $\pm$ 0.3
280	0.1 $\pm$ 0.0	4.3 $\pm$ 0.1	0.3 $\pm$ 0.1	6.7 $\pm$ 0.2	1.8 $\pm$ 0.6	17.4 $\pm$ 1.6	3.4 $\pm$ 0.7	8.8 $\pm$ 1.4	2.6 $\pm$ 0.7	4.4 $\pm$ 1.1	2.4 $\pm$ 0.6	4.7 $\pm$ 0.8
281	0.2 $\pm$ 0.1	0.4 $\pm$ 0.1	0.3 $\pm$ 0.1	0.7 $\pm$ 0.1	1.8 $\pm$ 0.5	4.8 $\pm$ 0.9	2.1 $\pm$ 0.4	2.5 $\pm$ 0.3	1.5 $\pm$ 0.5	1.7 $\pm$ 0.5	1.0 $\pm$ 0.3	1.0 $\pm$ 0.3
291	0.0 $\pm$ 0.1	0.1 $\pm$ 0.1	0.3 $\pm$ 0.0	2.5 $\pm$ 0.1	1.3 $\pm$ 0.5	3.1 $\pm$ 0.6	2.7 $\pm$ 0.7	4.1 $\pm$ 0.6	2.2 $\pm$ 1.0	3.2 $\pm$ 0.9	1.2 $\pm$ 0.4	1.2 $\pm$ 0.4
298	0.3 $\pm$ 0.1	1.9 $\pm$ 0.3	0.4 $\pm$ 0.1	3.1 $\pm$ 0.4	1.4 $\pm$ 0.4	5.8 $\pm$ 0.7	1.9 $\pm$ 0.6	2.8 $\pm$ 0.7	1.0 $\pm$ 0.6	1.0 $\pm$ 0.5	0.2 $\pm$ 0.3	0.1 $\pm$ 0.3
316	0.3 $\pm$ 0.1	3.5 $\pm$ 0.2		57.1 $\pm$ 5.7		44.1 $\pm$ 8.8	0.2 $\pm$ 0.3	17.8 $\pm$ 1.8	0.2 $\pm$ 0.2	6.3 $\pm$ 0.6	0.0 $\pm$ 0.3	2.2 $\pm$ 0.2

Table 5. Table 8: Size-scaled and color-corrected fluxes in the Herschel bands

ID	$S_{100}$	$S_{160}$	$S_{250}$	$S_{350}$	$S_{500}$
	Jy	Jy	Jy	Jy	Jy
1	233.9 $\pm$ 9.0	187.5 $\pm$ 10.2	86.8 $\pm$ 5.7	36.1 $\pm$ 3.2	18.5 $\pm$ 2.0
2	33.5 $\pm$ 1.1	43.1 $\pm$ 3.0	23.7 $\pm$ 1.3	13.7 $\pm$ 1.3	5.5 $\pm$ 0.6
3	227.0 $\pm$ 6.9	199.3 $\pm$ 10.7	90.8 $\pm$ 4.6	37.7 $\pm$ 2.9	7.8 $\pm$ 1.1
4	17.9 $\pm$ 0.8	34.0 $\pm$ 2.2	26.6 $\pm$ 1.4	11.3 $\pm$ 1.2	8.9 $\pm$ 0.8
5	21.2 $\pm$ 1.0	30.0 $\pm$ 2.7	9.8 $\pm$ 0.9	2.4 $\pm$ 1.1	3.5 $\pm$ 0.7
8	47.7 $\pm$ 3.5	60.5 $\pm$ 4.3	51.8 $\pm$ 2.7	33.4 $\pm$ 2.6	17.4 $\pm$ 1.5
10	9.5 $\pm$ 0.5	10.1 $\pm$ 1.0	4.0 $\pm$ 1.3
11	51.5 $\pm$ 1.6	42.5 $\pm$ 2.2	18.1 $\pm$ 1.1	8.7 $\pm$ 1.2	3.1 $\pm$ 1.2
15	13.7 $\pm$ 0.5	10.4 $\pm$ 0.6	5.5 $\pm$ 0.4	2.1 $\pm$ 0.3	1.6 $\pm$ 0.4
16	25.0 $\pm$ 1.1	38.9 $\pm$ 2.3	29.5 $\pm$ 1.5	20.6 $\pm$ 1.9	9.9 $\pm$ 1.0
19		27.2 $\pm$ 2.4	14.8 $\pm$ 1.7	10.4 $\pm$ 1.3	4.9 $\pm$ 0.9
28	10.1 $\pm$ 0.4	13.1 $\pm$ 1.3	7.1 $\pm$ 0.7	2.7 $\pm$ 0.7	2.0 $\pm$ 0.6
32	12.5 $\pm$ 0.6	10.7 $\pm$ 0.7	3.7 $\pm$ 0.4	1.2 $\pm$ 0.3	0.8 $\pm$ 0.6
33	14.6 $\pm$ 0.7	22.4 $\pm$ 1.6	12.3 $\pm$ 1.0	6.2 $\pm$ 0.9	2.8 $\pm$ 0.6
37	4.0 $\pm$ 0.9	10.5 $\pm$ 3.1	6.8 $\pm$ 2.3
42	17.6 $\pm$ 0.8	26.0 $\pm$ 1.7	11.5 $\pm$ 0.9	7.5 $\pm$ 0.8	4.0 $\pm$ 1.0
44	18.7 $\pm$ 0.9	21.8 $\pm$ 1.5	5.0 $\pm$ 0.7	3.2 $\pm$ 0.8	1.9 $\pm$ 0.6
45	3.4 $\pm$ 0.5	22.4 $\pm$ 1.7	25.9 $\pm$ 1.4	12.2 $\pm$ 1.3	8.8 $\pm$ 0.8
47		30.6 $\pm$ 5.1	22.5 $\pm$ 3.4	11.8 $\pm$ 2.1	5.3 $\pm$ 0.9
49		9.1 $\pm$ 0.9	4.8 $\pm$ 0.5	2.0 $\pm$ 0.2	5.7 $\pm$ 0.6
51	5.5 $\pm$ 0.4	16.0 $\pm$ 1.5	13.9 $\pm$ 0.9	6.6 $\pm$ 1.1	3.8 $\pm$ 0.6
58	8.7 $\pm$ 0.5	9.7 $\pm$ 0.8	4.8 $\pm$ 0.5	1.4 $\pm$ 0.7
61		5.6 $\pm$ 0.7	19.8 $\pm$ 1.8	11.3 $\pm$ 1.0	7.7 $\pm$ 0.9
69	9.6 $\pm$ 1.1	12.4 $\pm$ 1.1	8.8 $\pm$ 0.6	3.2 $\pm$ 0.4	1.1 $\pm$ 0.3
72	17.0 $\pm$ 0.8	16.5 $\pm$ 1.4	6.0 $\pm$ 0.9	2.9 $\pm$ 0.8
85	5.7 $\pm$ 0.9	13.1 $\pm$ 2.9	13.3 $\pm$ 2.7	7.5 $\pm$ 1.6	6.2 $\pm$ 1.0
86		4.8 $\pm$ 0.3	2.3 $\pm$ 0.2	1.1 $\pm$ 0.1
89	10.8 $\pm$ 0.6	10.9 $\pm$ 0.8	5.1 $\pm$ 0.6	2.4 $\pm$ 0.8	1.9 $\pm$ 0.7
90	8.3 $\pm$ 0.5	18.1 $\pm$ 1.0	11.8 $\pm$ 0.8	6.2 $\pm$ 0.6	2.3 $\pm$ 0.7
92		5.8 $\pm$ 0.6	4.3 $\pm$ 0.5	2.5 $\pm$ 0.3	1.6 $\pm$ 0.2
111	2.1 $\pm$ 0.1	4.1 $\pm$ 0.4	2.3 $\pm$ 0.3	0.7 $\pm$ 0.3
115	1.6 $\pm$ 0.3	2.8 $\pm$ 0.7	1.3 $\pm$ 0.5	0.7 $\pm$ 0.3
132		2.7 $\pm$ 0.2	2.0 $\pm$ 0.4	0.5 $\pm$ 0.4
141	8.0 $\pm$ 0.8	11.1 $\pm$ 2.2	7.6 $\pm$ 0.8	2.0 $\pm$ 0.2	1.5 $\pm$ 0.2
154	8.5 $\pm$ 0.6	11.1 $\pm$ 1.1	5.6 $\pm$ 0.6	1.9 $\pm$ 0.8	1.0 $\pm$ 0.4
161	7.0 $\pm$ 0.4	10.2 $\pm$ 0.9	5.7 $\pm$ 1.0		0.6 $\pm$ 0.3
263			22.2 $\pm$ 1.7	11.4 $\pm$ 1.3	6.3 $\pm$ 0.8
265		8.6 $\pm$ 1.1	6.4 $\pm$ 0.9	4.2 $\pm$ 1.0	1.4 $\pm$ 0.4
268		6.5 $\pm$ 0.7	6.4 $\pm$ 0.7	3.2 $\pm$ 0.5	1.2 $\pm$ 0.4
270			19.4 $\pm$ 1.7	10.8 $\pm$ 1.2	5.6 $\pm$ 0.9
271	10.6 $\pm$ 0.4	14.9 $\pm$ 0.9	7.5 $\pm$ 0.6	3.8 $\pm$ 0.4	1.3 $\pm$ 0.2
272			21.9 $\pm$ 1.5	12.2 $\pm$ 1.3	8.5 $\pm$ 1.0
273	9.0 $\pm$ 0.6	8.6 $\pm$ 0.9	4.6 $\pm$ 0.6	1.7 $\pm$ 0.7
274		2.5 $\pm$ 0.3	3.1 $\pm$ 0.4	1.5 $\pm$ 0.4
278	0.5 $\pm$ 0.1	1.4 $\pm$ 0.4	1.6 $\pm$ 0.5
280			8.3 $\pm$ 1.4	4.3 $\pm$ 1.1	2.3 $\pm$ 0.8
281		4.5 $\pm$ 0.9	2.4 $\pm$ 0.3	1.0 $\pm$ 0.4
291		2.5 $\pm$ 0.6	3.9 $\pm$ 0.6	2.8 $\pm$ 0.8
298	3.2 $\pm$ 0.4	6.0 $\pm$ 0.8	2.6 $\pm$ 0.7
316	57.1 $\pm$ 5.7	44.1 $\pm$ 8.8	17.8 $\pm$ 1.8	6.3 $\pm$ 0.6	2.2 $\pm$ 0.2

Table 6. Table 9: Observed properties of compact sources

ID	Photometriesa	IR Counterpartb	Blended Source	Hosting Condensationc	Classd	Commentse
1	(100,160,250,350,500) $\mu$m	(3.6,4.5,5.8,8.0,12,24,70) $\mu$m	no	cond-2	I	91C2, class I, high-mass YSO
2	(100,160,250,350,500) $\mu$m	(2.17,3.6,4.5,5.8,8.0,12,24,70) $\mu$m	51	cond-3	IM	3C3, class I
3	(100,160,250,350,500) $\mu$m	(3.6,4.5,5.8,8.0,24,70) $\mu$m	8	cond-4	I	2C4, class I
4	(100,160,250,350,500) $\mu$m	(1.25,1.65,2.17,3.6,4.5,5.8,8.0,24,70) $\mu$m	no	cond-3	IM	class I
5	(100,160,250,350,500) $\mu$m	(1.25,1.65,2.17,3.6,4.5,5.8,8.0,12,24,70) $\mu$m	2,51	cond-3	I	2C3, class I
8	(100,160,250,350,500) $\mu$m	(3.6,4.5,5.8,8.0) $\mu$m	3	cond-4	IM	3C4, class I
10	(100,160,250) $\mu$m	(3.6,4.5,5.8,8.0,12,24,70) $\mu$m	no	cond-1	I	237C2, class I, high-mass YSO
11	(100,160,250,350,500) $\mu$m	(1.25,1.65,2.17,3.6,4.5,5.8,8.0,70) $\mu$m	no	cond-9	I	class I
15	(100,160,250,350,500) $\mu$m	Filaments at [3.6,4.5,5.8,8.0,12,24,70] $\mu$m	no	SW	I	I
16	[100](160,250,350,500) $\mu$m	Filaments at [3.6,4.5,5.8,8.0,12,24,70] $\mu$m	no	cond-3	0	class 0
19	(160,250,350,500) $\mu$m	(3.6,4.5,5.8,8.0,24) $\mu$m	no	cond-3	IM	1C3, class I
28	(100,160,250,350,500) $\mu$m	(1.65,2.17,3.6,4.5) $\mu$m	no	cond4below	I	class I
32	(100,160,250,350,500) $\mu$m	Filaments at [3.6,4.5,5.8,8.0,12,24,70] $\mu$m	no	SW	I	class I
33	[100](160,250,350,500) $\mu$m	[8.0,12,24,70] $\mu$m	no	cond2below	IM	IM
37	(100,160,250) $\mu$m	[5.8,8.0,12,24,70] $\mu$m	no	cond-2	IM	IM
42	(100,160,250,350,500) $\mu$m	[5.8,8.0,12,24,70] $\mu$m	no	cond-5	IM	IM
44	(100,160,250,350,500) $\mu$m	Filaments at [3.6,4.5,5.8,8.0,12,24,70] $\mu$m	no	SW	IM	IM
45	(100,160,250,350,500) $\mu$m	[5.8,8.0] $\mu$m	no	cond-3	0	class 0
47	(160,250,350,500) $\mu$m	[5.8,8.0,12,24,70] $\mu$m	no	cond-2	0	class 0
49	(160,250,350,500) $\mu$m	[5.8,8.0,12,24,70] $\mu$m	no	cond-2	IM	IM
51	(100,160,250,350,500) $\mu$m	(2.17,3.6,4.5,5.8,8.0) $\mu$m	2,4	cond-3	0	5C3, class I
58	(100,160,250,350) $\mu$m	[5.8,8.0,12,24,70] $\mu$m	no	cond-4	IM	IM
61	[160](250,350,500) $\mu$m	Absorption at [5.8,8.0,12] $\mu$m	no	cond-8	0	class 0
69	(100,160,250,350,500) $\mu$m	Filaments at [3.6,4.5,5.8,8.0,12,24,70] $\mu$m	no	SW	IM	IM
72	(100,160,250,350) $\mu$m	Filaments at [3.6,4.5,5.8,8.0,12,24,70] $\mu$m	no	SW	IM	IM
85	(100,160,250,350,500) $\mu$m	[3.6,4.5,5.8,8.0,12,24] $\mu$m	no	cond-2	0	class 0
86	(100,160,250,350,500) $\mu$m	[3.6,4.5,5.8,8.0,70] $\mu$m	no	Center	IM	IM
89	(100,160,250,350,500) $\mu$m	[5.8,8.0,12,24,70] $\mu$m	95	cond-4	IM	IM
90	[100](160,250,350,500) $\mu$m	Absorption at [8,12,24] $\mu$m	no	cond-7	0	class 0
92	(160,250,350,500) $\mu$m	Absorption at [8,12,24] $\mu$m	no	NE	0	class 0
111	(100,160,250,350,500) $\mu$m	[5.8,8.0,12,24,70] $\mu$m	no	cond-4	IM	IM
115	(100,160,250,350) $\mu$m	[5.8,8.0,12,24,70] $\mu$m	no	cond3below	IM	IM
132	(160,250,350) $\mu$m	[12,24,70] $\mu$m	no	NE	IM	IM
141	(160,250,350,500) $\mu$m	Absorption at [8.0] $\mu$m	no	cond-2	IM	AC2, class I
154	(100,160,250,350,500) $\mu$m	Filaments at [5.8,8.0,12,24,70] $\mu$m	no	cond2below	IM	IM
161	[100](160,250,500) $\mu$m	Filaments at [5.8,8.0,12,24,70] $\mu$m	no	cond2below	IM	IM
263	(250,350,500) $\mu$m	Absorption at [8.0,12,24] $\mu$m	no	cond-4	0	class 0
265	(160,250,350,500) $\mu$m	Absorption at [8.0,12,24] $\mu$m	no	cond-1	0	class 0
268	(160,250,350,500) $\mu$m	Absorption at [8.0,12,24] $\mu$m	no	cond3below	0	class 0
270	(250,350,500) $\mu$m	Absorption at [8.0,12,24,70] $\mu$m	no	cond-5	0	class 0
271	(100,160,250,350,500) $\mu$m	[8.0,12,24,70] $\mu$m	no	NE	IM	IM
272	(250,350,500) $\mu$m	Absorption at [8.0,12,24,70] $\mu$m	no	cond-4	0	class 0
273	(100,160,250,350) $\mu$m	[8.0,12,24,70] $\mu$m	no	cond-4	IM	IM
274	(160,250,350) $\mu$m	Absorption at [8.0,12,24,70] $\mu$m	no	cond-4	0	class 0
278	(100,160,250) $\mu$m	Absorption at [8.0,12,24,70] $\mu$m	no	cond-4	0	class 0
280	(250,350,500) $\mu$m	Absorption at [8.0,12,24,70] $\mu$m	no	cond-9	0	class 0
281	(160,250,350) $\mu$m	[8.0,12,24,70] $\mu$m	no	cond2below	I	class I
291	(160,250,350) $\mu$m	[5.8,8.0,12,24,70] $\mu$m	no	cond-2	0	class 0
298	(100,160,250) $\mu$m	[5.8,8.0,12,24,70] $\mu$m	no	cond-4	IM	IM
316	[100](160,250,350,500) $\mu$m	[5.8,8.0,12,24,70] $\mu$m	no	cond-2	I	class I

Table 7. Table 10: Photometries in the NIR and MIR bands for 11 compact sources

ID	Designation	$J$	$H$	$Ks$	$I1$	$I2$	$I3$	$I4$	$12$ $\mu$m	$24$ $\mu$m
		mJy	mJy	mJy	mJy	mJy	mJy	mJy	mJy	mJy
1	G308.7543+00.5486				20.4 $\pm$ 0.8	107.7 $\pm$ 13.8	156.7 $\pm$ 8.6	210.0 $\pm$ 9.3	353.5 $\pm$ 7.4	6959.4 $\pm$ 57.3
2	G308.6874+00.5240			6.2 $\pm$ 0.3	57.9 $\pm$ 10.0	278.6 $\pm$ 17.7	532.4 $\pm$ 17.1	487.6 $\pm$ 16.6	74.5 $\pm$ 2.5	1272.5 $\pm$ 26.4
3	G308.6467+00.6458				9.7 $\pm$ 3.0	23.2 $\pm$ 3.8	178.6 $\pm$ 19.6	456.8 $\pm$ 67.7		946.0 $\pm$ 23.6
4	G308.6884+00.5279	1.0 $\pm$ 0.5	6.1 $\pm$ 1.9	3.8 $\pm$ 0.3	5.0 $\pm$ 0.7	12.6 $\pm$ 1.6	16.8 $\pm$ 1.0	27.2 $\pm$ 2.6		242.2 $\pm$ 10.0
5	G308.7009+00.5315	3.7 $\pm$ 0.1	7.8 $\pm$ 0.3	12.5 $\pm$ 0.4	43.0 $\pm$ 13.8	43.5 $\pm$ 4.6	259.0 $\pm$ 12.8	668.2 $\pm$ 36.3	680.0 $\pm$ 8.0	6633.2 $\pm$ 56.8
8	G308.6465+00.6503				20.1 $\pm$ 1.6	49.1 $\pm$ 3.6	95.4 $\pm$ 3.9	129.5 $\pm$ 7.5
10	G308.7681+00.5706				11.0 $\pm$ 0.7	45.0 $\pm$ 2.3	112.7 $\pm$ 4.1	162.3 $\pm$ 9.0	42.2 $\pm$ 1.8	759.4 $\pm$ 14.4
11	G308.6729+00.6335	6.5 $\pm$ 0.8	16.7 $\pm$ 0.8	51.0 $\pm$ 1.6	86.5 $\pm$ 9.2	95.3 $\pm$ 8.1	128.8 $\pm$ 11.8	178.8 $\pm$ 25.8
19	G308.7129+00.5349				34.5 $\pm$ 2.9	65.5 $\pm$ 3.4	114.2 $\pm$ 7.5	122.0 $\pm$ 27.8		168.9 $\pm$ 6.1
28			1.3 $\pm$ 1.8	3.5 $\pm$ 3.3	1.6 $\pm$ 0.1	1.3 $\pm$ 0.1
51	G308.6895+00.5253			3.7 $\pm$ 0.3	31.4 $\pm$ 3.5	78.0 $\pm$ 6.4	134.9 $\pm$ 9.0	140.6 $\pm$ 7.2

Equations

$$L_{\mathrm{bol}}=4\pi D^2\int F_{\nu }\mathrm{d}\nu .$$

$$F_{\nu }=\frac{{\kappa }_{\nu }{B}_{\nu }(T_{\mathrm{d}})M_{\mathrm{env}}}{D^2},$$

$$F_{\lambda }^{scaled}=F_{\lambda }^{original}\left(\frac{FWH{M}_{ref}^{dec}}{FWH{M}_{\lambda }^{dec}}\right),$$

$$FWH{M}_{\lambda }^{dec}=\sqrt{{FWH{M}_{\lambda }^{obs}}^2-{HPB{W}_{\lambda }}^2},$$

Full text

*Aims. *We aim to obtain a census of the young stellar population observed at the edges of the H ii region and to determine the properties of the young sources in order to characterize the star formation processes that take place at the edges of this ionized region.

*Methods. *We take advantage of Herschel data from the surveys HOBYS, “Evolution of Interstellar Dust”, and Hi-Gal to extract compact sources. We use the algorithm getsources. We complement the Herschel data with archival 2MASS, Spitzer, and WISE data to determine the physical parameters of the sources (e.g., envelope mass, dust temperature, and luminosity) by fitting the spectral energy distribution.

Results. We created the dust temperature and column density maps along with the column density probability distribution function (PDF) for the entire RCW 79 region. We obtained a sample of 50 compact sources in this region, $96\%$ of which are situated in the ionization-compressed layer of cold and dense gas that is characterized by the column density PDF with a double-peaked lognormal distribution. The 50 sources have sizes of $\sim 0.1-0.4$ pc with a typical value of $\sim 0.2$ pc, temperatures of $\sim 11-26$ K, envelope masses of $\sim 6-760$ $M_{\odot}$, densities of $\sim 0.1-44\times 10^{5}$ cm-3, and luminosities of $\sim 19-12712$ $L_{\odot}$. The sources are classified into 16 class 0, 19 intermediate, and 15 class I objects. Their distribution follows the evolutionary tracks in the diagram of bolometric luminosity versus envelope mass ($L_{\rm bol}-M_{\rm env}$) well. A mass threshold of 140 $M_{\odot}$, determined from the $L_{\rm bol}-M_{\rm env}$ diagram, yields 12 candidate massive dense cores that may form high-mass stars. The core formation efficiency (CFE) for the 8 massive condensations shows an increasing trend of the CFE with density. This suggests that the denser the condensation, the higher the fraction of its mass transformation into dense cores, as previously observed in other high-mass star-forming regions.

1 Introduction

H ii regions or bubbles are ubiquitous in the Milky Way. Taking advantage of the Spitzer-GLIMPSE (Benjamin et al. 2003) and MIPSGAL (Carey et al. 2005) surveys, Churchwell et al. (2006, 2007) cataloged the first largest sample of about 600 infrared (IR) dust bubbles in longitudes $|l|\leq 65\degr$. The comparison of these bubbles with the H ii region catalog of Paladini et al. (2003) indicates that about $12-25\%$ of the bubbles are overlapping with H ii regions (Churchwell et al. 2006, 2007). This fraction is probably a lower limit because the H ii region catalog is incomplete, especially for the H ii regions with small diameters (Churchwell et al. 2007). Indeed, the fraction can reach $\sim\leavevmode\nobreak\ 86\%$ (Deharveng et al. 2010) and even more (Bania et al. 2010; Anderson et al. 2011). These results imply a significant correlation between bubbles and Galactic H ii regions. Based on the same surveys, a larger sample of more than 5000 IR bubbles has been visually identified by citizen scientists recruited online (Simpson et al. 2012). Moreover, using data from the all-sky Wide-Field Infrared Survey Explorer (WISE) satellite, Anderson et al. (2014) have made a catalog of over 8000 Galactic H ii regions and H ii region candidates by searching for their characteristic mid-infrared (MIR) bubble morphology.

It is suggested that triggered star formation might occur around H ii regions or bubbles. For instance, Deharveng et al. (2010) studied the association of 102 Churwell’s bubbles with the dense condensations revealed by the ATLASGAL 870 $\mu$m continuum survey data (Schuller et al. 2009). Their study suggested that more than $25\%$ of bubbles may have triggered the formation of high-mass stars. In addition, analyzing the association of Red Mid-course Space Experiment (MSX, Price et al. 2001) massive young stellar objects111A massive young stellar object (MYSO) is an embedded infrared source that is luminous enough to be a young O- or B-type star, but has not yet formed an H ii region (e.g., Urquhart et al. 2007; Mottram et al. 2007) (MYSOs) with 322 Churwell’s bubbles, Thompson et al. (2012) suggested that about $14-30\%$ of high-mass star formation in the Milky Way might have been triggered by the expanding H ii regions or bubbles. Similarly, the study of the association of MYSOs with 1018 bubbles from the Simpson et al. (2012) catalog indicated that around $22\pm 2\%$ of MYSO formation might have been induced by the expansion of the H ii regions or bubbles (Kendrew et al. 2012). These results suggest that triggered star formation around H ii regions or bubbles may be an important process, especially for high-mass star formation (e.g., Deharveng et al. 2010; Kendrew et al. 2016).

Triggered star formation may cause the increase of the clump and/or core formation efficiency (CFE), which is analogous to the star formation efficiency (SFE, e.g., Motte et al. 2007; Bontemps et al. 2010b; Eden et al. 2012). For example, in the W3 giant molecular cloud, which is a Galactic high-mass star-forming region, Moore et al. (2007) found that the CFE is around $5-13\%$ in the undisturbed cloud, but about $25-37\%$ in the feedback-affected region, which is indicative of an increase in CFE. Furthermore, Eden et al. (2012) reported a local increase in CFE in the W43 H ii region, which may be associated with the triggering of star formation in its vicinity (Bally et al. 2010). In addition, the increases in CFE have been predicted by the simulation of Dale et al. (2007). Their simulation with feedback from an H ii region results in an SFE approximately one-third higher than in the control run without feedback.

In spite of its importance, triggered star formation remains difficult to be clearly identified (e.g., Elmegreen 2011; Dale et al. 2013; Liu et al. 2015; Dale et al. 2015). It is difficult to distinguish stars formed by triggering from those forming spontaneously (Elmegreen 2011; Dale et al. 2015). The high surface density of YSOs observed at the edge of H ii regions or bubbles is often assumed to be a result of triggered star formation (Zavagno et al. 2006; Deharveng et al. 2009; Thompson et al. 2012; Kendrew et al. 2012; Liu et al. 2015, 2016; Yadav et al. 2016; Nandakumar et al. 2016). However, these YSOs might either be redistributed by the expansion of H ii regions or bubbles, or they might form in situ (Elmegreen 2011; Liu et al. 2015; Dale et al. 2015). Moreover, the incompleteness of YSOs, especially for the youngest protostars that are deeply embedded in dense clouds, prevents us from restoring their true spatial distribution (Liu et al. 2015). These facts make it difficult to draw a convincing conclusion on triggered star formation around ionized regions.

Herschel observations (Pilbratt et al. 2010), with their unprecedented angular resolutions and sensitivities in the far-IR regime, allow us to study the young stellar population in detail and to assess the importance of triggered star formation. The large wavelength coverage of Herschel (70$-$500 $\mu$m) and the high sensitivity allow the detection of highly embedded YSOs (e.g., class 0 objects) that cannot be detected at shorter wavelengths because of their low luminosity and high extinction (Zavagno et al. 2010). Therefore, Herschel observations allow us to obtain a census of the YSO population in all evolutionary stages around ionized region for a better study of the impact of high-mass stars on their surrounding. Indeed, more class 0 candidates have been detected with *Herschel *observations in different star-forming regions (e.g., Motte et al. 2010; Zavagno et al. 2010; Hennemann et al. 2010; Deharveng et al. 2012; Giannini et al. 2012; Samal et al. 2014; Deharveng et al. 2015). Furthermore, the spectral energy distribution (SED) of YSOs can be better constrained by the large FIR wavelength coverage, leading to more accurate estimates of their physical parameters such as the envelope mass, dust temperature, and bolometric luminosity. The luminosity-mass diagram is a useful tool to infer the evolutionary properties of the YSOs (Molinari et al. 2008, 2016). Moreover, Herschel images allow us to obtain reliable catalogs of compact sources (core/clumps, Figueira et al. (2016), and Tigé et al. 2016, submitted). This allows us to estimate the CFEs on smaller scales toward H ii regions. This is crucial for studying the influence of ionized regions on local star formation.

RCW 79 is a textbook example of an H ii region where triggered star formation might have taken place (Zavagno et al. 2006, hereafter ZA06). In this paper, we analyze the star formation observed around this region, using Herschel data from the surveys HOBYS222The Herschel imaging survey of OB Young Stellar objects (HOBYS) is a Herschel key programme. See http://hobys-herschel.cea.fr (Motte et al. 2010) and “Evolution of Interstellar Dust” (Abergel et al. 2010), complemented with 2MASS, Spitzer, and WISE data. Our purposes are to search for clumps that may form high-mass stars, to explore the star formation evolutionary scenarios, and to investigate the CFEs in RCW 79. This paper is organized as follows: we present RCW 79 in Sect. 2, the Herschel observations together with other archival data sets are described in Sect. 3, the results are presented in Sect. 4, and the discussion is given in Sect. LABEL:sect:discuss, followed by our conclusions in Sect. 6.

2 Presentation of RCW 79

RCW 79 (Rodgers et al. 1960) is a bright optical H ii region ionized by a cluster of a dozen O stars, the two most massive of which have a spectral type O4-6V/III (Martins et al. 2010). The ionizing luminosity of the ionizing stars was estimated to be $10^{3}$ times higher than the mechanical luminosity of their stellar winds (Martins et al. 2010), indicating a radiation-driven H ii region. This region is spatially encompassed by an almost complete dust ring (see Fig. 1), with a diameter of $\sim 12\arcmin$ , which corresponds to 12.8 pc at a distance of 4.3 kpc (ZA06). The ring structure was revealed with a velocity range of $-50$ to $-44$ km s*-1* in the observations of 12CO, 13CO, and C18O (J=1-0) (Saito et al. 2001). It is in good agreement with the velocity range of $-51$ to $-40$ km s*-1* measured for ionized gas (ZA06), indicative of a good association of the dust ring with the H ii region.

Figure 1 shows the composite three-color image of RCW 79 where blue, green, and red code the Spitzer 8.0 and 24 $\mu$m and the Herschel 70 $\mu$m, respectively. An unsharp masking333The module scipy.ndimage for multidimensional gradient magnitude using Gaussian derivatives is available at http://docs.scipy.org/doc/scipy/reference/py-modindex.html. was applied to the 70 $\mu$m image to filter out diffuse emission and enhance the contrast of intense emission in the images. As shown in Fig. 1, the dust ring is seen at both 8.0 and 70 $\mu$m. Emission at 8.0 $\mu$m mainly comes from polycyclic aromatic hydrocarbons (PAHs) at 7.7 and 8.6 $\mu$m, indicative of photoionization regions (PDRs, e.g., Pavlyuchenkov et al. 2013) which indicate the interplay between ionized gas and the adjacent neutral cloud. The 70 $\mu$m emission mainly traces hot components such as very small grains (VSGs) or warm material heated by protostars. Therefore, the appearance of the dust ring at both 8.0 and 70 $\mu$m demonstrates that the enclosed H ii region is interacting with and heating its vicinity. The 24 $\mu$m emission is predominantly distributed in the direction of the H ii region. This spatial distribution is in good agreement with the fact that 24 $\mu$m emission mainly arises from hot dust, which can reach rather high temperatures after absorbing high-energy photons (e.g. Deharveng et al. 2010; Liu et al. 2016).

SEST-SIMBA 1.2 mm continuum observations with an angular resolution of $24\arcsec$ revealed three highest mass fragments in the dust ring (see ZA06). For this, ESO-NTT SOFI near-IR and Spitzer GLIMPSE mid-IR data were combined to study the young stellar population observed toward this region. Nineteen class I YSO candidates (see Fig. 1) were found to be associated with the three fragments. In addition, one compact H ii region (CH ii) is embedded in the most massive fragment in the southeast region of the ring. Martins et al. (2010) furthermore observed 8 out of the 19 YSOs with the near-IR integral field spectragraph SINFONI mounted on the VLT telescope. All present spectral features typical of YSOs. All lines have velocities similar to that of the ionized gas, confirming the association of these YSOs with the region. The dust ring is opened in the northwest. The H$\alpha$ velocity field of ionized gas shows a flow through the hole with a few km s*-1* (see Fig. 12 of ZA06). This flow was interpreted as a champagne phenomenon, indicating a strong interaction of RCW 79 with its surrounding material (ZA06). Moreover, combining the model of Whitworth et al. (1994), ZA06 found that the ring of collected gas had enough time to fragment during the lifetime of RCW 79, and that the radius and mass of the fragments basically agree with the values predicted by the model. Therefore, ZA06 concluded that the YSOs at the edge of RCW 79 might have been triggered by the expanding H ii region.

An elongated clump (i.e., RegA) is located about 6 pc away from the northeast edge of RCW 79 (see Fig. 1). This clump is associated with 8 $\mu$m emission, suggesting influences from ionized gas. The northeastern ring orthogonal to the clump appears diffuse relative to its neighbors. This diffuse characteristic implies that the clump could be photoionization-shaped by the leaking photons from the H ii region through the diffuse ring, as shown in Fig. 2(c). Additionally, there are two other extended filamentary features (e.g., RegB and RegC) situated to the south and southwest of RCW 79, respectively. Based on the observations of 12CO, and 13CO (J=1-0) (Saito et al. 2001), these two features have the same velocity as RCW 79, which means that they may be associated. As shown in Fig. 1, these two features are associated with PDRs, as seen in 8 $\mu$m emission. Likewise, the two features could be a consequence of photoionization by the leaking photons from RCW 79, as discussed in Sect. 4.1.

3 Observations and data reduction

3.1 Herschel observations

RCW 79 was observed as part of the HOBYS (Motte et al. 2010) and “Evolution of Interstellar Dust” (Abergel et al. 2010) guaranteed time key programs. The Photodetector Array Camera & Spectrometer (PACS, Poglitsch et al. 2010) at 100 and 160 $\mu$m and the Spectral and Photometric Imaging Receiver (SPIRE, Griffin et al. 2010) at 250, 350, and 500 $\mu$m were equipped to carry out both surveys with scan speeds of $20\arcsec$ per second for PACS and $30\arcsec$ per second for SPIRE. The angular resolutions of these five bands in order of increasing wavelength are 6$\aas@@fstack{\prime\prime}7$, 11$\aas@@fstack{\prime\prime}4$, 18$\aas@@fstack{\prime\prime}2$, 25$\arcsec$, and 36$\arcsec$. Table 1 lists the observation parameters including the mapping size, the total integration time, the observation identification number, and the observation date.

The Herschel data were processed using slightly modified versions of the default PACS and SPIRE pipelines built into the Herschel interactive processing environment (HIPE) software v. 10. The pipelines produced level 2 data, which to some extent suffer from striping artifacts in the in-scan directions and flux decrements around bright zones of emission resulting from the median-filtering baseline removal. To remove both artifacts, the Scanamorphos software (Roussel 2012), version 9, was used to create the final level 2 maps without the “Galactic” option. Additionally, the astrometry of all the maps was adjusted to be consistent with each other and with higher resolution Spitzer data.

The 70 $\mu$m image from the Hi-Gal survey (Molinari et al. 2010) was also retrieved to complement our observations. Its measured angular resolution is 10$\aas@@fstack{\prime\prime}7$ (Traficante et al. 2011). The detailed descriptions of the preprocessing of the data up to usable high-quality image can be found in Traficante et al. (2011).

The absolute calibration uncertainty for PACS is estimated to be $10\%$ at 70 and 100 $\mu$m and $20\%$ at 160 $\mu$m (see PACS observers’ manual444http://herschel.esac.esa.int/Docs/PACS/pdf/pacs\_om.pdf), while for SPIRE it is within $10\%$ for all bands (see SPIRE observers’ manual555http://herschel.esac.esa.int/Docs/SPIRE/spire\_handbook.pdf).

3.2 Archival data

To carry out a multiwavelength analysis of this region, ancillary infrared data were taken from the IRSA Archive.666http://irsa.ipac.caltech.edu/frontpage/ The J, H, Ks images at 1.25, 1.65, and 2.17 $\mu$m with a resolution of $4\arcsec$ were retrieved from the Two Micron All Sky Survey (2MASS, Skrutskie et al. 2006). In addition, the images of the Spitzer Infrared Array Camera (IRAC) at 3.6, 4.5, 5.8, and 8.0 $\mu$m, together with the Multiband imaging photometer for Spitzer (MIPS) at 24 $\mu$m, were obtained from the GLIMPSE (Benjamin et al. 2003) and MIPSGAL (Carey et al. 2005) surveys, respectively. The resolutions in the IRAC bands are better than $2\arcsec,$ and the resolution is $6\arcsec$ in the MIPS 24 $\mu$m band. Moreover, the 12 $\mu$m image with a resolution of $6\aas@@fstack{\prime\prime}5$ was used from the WISE survey (Wright et al. 2010). This survey provides the images in four wavelength bands, but the 3.4 and 4.6 $\mu$m bands were not taken into account because their resolutions are lower than those of the IRAC 3.6 and 4.5 $\mu$m bands. We did not make use of the 22 $\mu$m data either because negative values appear in the majority of pixels of the image covering RCW 79.

4 Results

4.1 Dust temperature and column density maps

The dust temperature ($T_{\mathrm{dust}}$) and column density ($N_{\mathrm{H_{2}}}$) maps of RCW 79 were created using a modified blackbody model to fit the SEDs pixel by pixel, as described by Hill et al. (2012a, b). Before the SED fitting, all Herschel images except for the 70 $\mu$m image were convolved to the resolution of the 500 $\mu$m band and then regridded to the same pixel size as that of the 500 $\mu$m image. Emission at 70 $\mu$m  was excluded in the SED fitting because it can be contaminated by emission from small grains in hot PDRs. In the SED fitting, a dust opacity law of $\kappa_{\nu}=0.1\times(\nu/1\mathrm{THz})^{\beta}$ was adopted with a gas-to-dust mass ratio of 100 (Beckwith et al. 1990). $\beta=2$ was fixed to be consistent with other papers of the HOBYS consortium. Additionally, to reveal more small structures, a high-resolution ($18\aas@@fstack{\prime\prime}2$) column density map was made based on the method of Hill et al. (2012a). The 36$\arcsec$ resolution $T_{\mathrm{dust}}$ and $18\aas@@fstack{\prime\prime}2$ resolution $N_{\mathrm{H_{2}}}$ maps are presented in Fig. 2.

In Fig. 2 (a) the dust temperature distribution on the large scale almost agrees with the 24 $\mu$m emission. As mentioned in Sect. 2, this 24 $\mu$m  emission traces hot dust heated by high-energy ionizing photons, which can be demonstrated by the good spatial coincidence of 24 $\mu$m emission with ionized gas seen by the H$\alpha$ emission (see Fig. 2 (c)). On the small scale, we see the four main hottest regions (HRs 1-4) with a range of 23.5 to 27 K (see Fig. 2 a-b). The first two (HR1 and HR2) are located in the direction of the H ii region, spatially overlapping with dense ionized gas (see Fig. 2 (c)). The other two (HR3 and HR4) are located on the southwestern and southeastern edges of RCW 79, respectively, where they are exposed to ionized gas. These four hottest regions could in large part be a consequence of their exposure to the heating of ionized gas. Additionally, the hottest of the four regions (HR3) is situated on the southeastern edge (see Fig. 2 a-b), but it is the farthest from the cluster of ionizing stars of RCW 79. Given the association of this region with the CH ii region, the highest temperature can be attributed to an additional heating from the CH ii region. In contrast, there are five cold regions (CRs 1-5) with lower temperatures ($\sim 17.5-20$ K, see Fig. 2 (a-b)). These five coldest regions are all spatially coincident with the column density peaks. The first two regions (CR1 and CR2) lie on the southern edge, the third region (CR3) lies on the western edge, and the remaining two regions (CR4 and CR5) lie in the northern area of RCW 79. For these regions, the anticorrelation between their temperatures and column densities suggests that their low temperatures could arise, in part, from a lower penetration of the external heating from the H ii region into dense regions (Liu et al. 2016).

Figure 2 (c) shows the column density map (red) superimposed on H$\alpha$ emission (turquoise) from the SuperCOSMOS survey (Parker & Phillipps 1998). The shell seen in the column density distribution encompasses ionized gas traced by H$\alpha$ emission, suggesting the strong impact that the enclosed H ii region has on its surroundings. The influence on the column density structure is discussed in more detail in Sect. 4.2. Of interest are two dark lanes of H$\alpha$ emission in the direction of the H ii region. Such characteristics have also been observed in RCW 120 (Anderson et al. 2015). The dark lanes of H$\alpha$ emission have been attributed to optical absorption by foreground material. As shown in Fig. 2 (c), lane 1 is indeed associated with column density enhancement with respect to its surrounding. Therefore, the dark lane 1 of ionized gas could be a result of optical absorption by foreground material. In contrast, lane 2 is not clearly related with enhanced column densities, indicating that lane 2 of ionized gas may not be caused predominantly by optical absorption of foreground clouds. In fact, lane 2 of the ionized gas is spatially well coincident with the central cavity, as inscribed at 24 $\mu$m in Fig. 2 (a). On the basis of hydrodynamical simulations, it is suggested that a young H ii region should not be strongly affected by stellar winds at the beginning of its evolution, but the winds eventually become stronger, giving rise to a very hot dust cavity (Capriotti & Kozminski 2001; Freyer et al. 2003, 2006). Such a cavity is probably shown in the 24 $\mu$m emission tracing hot dust (Watson et al. 2008; Liu et al. 2015). However, the dust cavity could also be caused by either the radiation pressure of ionizing stars or dust destruction by their intense radiation (Inoue 2002; Krumholz & Matzner 2009; Martins et al. 2010). In lane 2, ionized gas dark emission indicates no intense radiation in this cavity. Additionally, Martins et al. (2010) concluded that the effect of the stellar winds on the dynamics of RCW 79 is rather limited. Therefore, we suggest that lane 2 may arise from the dispersion of ionized gas by the strong radiation pressure from the cluster of ionizing stars. Diffuse ionized gas emission is observed outside the ionized region, indicated by arrows in Fig. 2 (c). These emissions can be due to the leaking of ionizing photons through density holes in the PDR, as has been suggested in Zavagno et al. (2007) (see their Fig. 2).

4.2 Probability distribution function

The impact of different physical processes (e.g., turbulence, gravity, or pressure) on the column density structure of a whole molecular cloud or parts of it can be studied using probability distribution functions (PDFs) of the column density. PDFs are frequently used in observations and theory (e.g., Kainulainen et al. 2009; Schneider et al. 2015b; Federrath & Klessen 2012, for an overview). Using Herschel dust maps, various studies showed that a lognormal shape of the PDF is consistent with low-density gas, dominated by turbulence (Schneider et al. 2013), and a single or double power-law tail appears for dense star-forming clouds (e.g., Hill et al. 2011; Russeil et al. 2013; Schneider et al. 2015a; Könyves et al. 2015), which is attributed to the effects of gravity (e.g., Girichidis et al. 2014, for an overview). Molecular clouds surrounding H ii regions (Schneider et al. 2012; Tremblin et al. 2014b) showed PDFs with two lognormal distributions (“double-peak” PDFs) or PDFs with a larger width, followed by a power-law tail. These observations were interpreted as an expansion of the ionized gas into the turbulent molecular cloud (representing the first lognormal form of the PDF), leading to a compression zone with higher densities that in turn cause the second peak, but are still dominated by turbulence. The widths of the two lognormal distributions of the PDFs and the distance between the peaks depend on the relative importance of ionization pressure and turbulent ram pressure (Tremblin et al. 2014b).

For this paper, we constructed a PDF777To be consistent with other Herschel studies, we used the visual extinction $A_{\rm v}$ instead of the hydrogen column density, linked by $N_{\rm H_{2}}=A_{\rm v}\times 0.94\times 10^{21}$ cm*-2* mag*-1* (Bohlin et al. 1978). of RCW 79 from the whole area observed with Herschel, using the high- and low-angular resolution maps (18*′′.2 and 36′′*, respectively). The PDFs do not differ much (see Schneider et al. 2015b; Ossenkopf-Okada et al. 2016, for resolution effects on PDFs), therefore we only present the PDF of the high-resolution map here. We did not perform a background subtraction, as recommended by Schneider et al. (2015b), because the map of RCW 79 is too small to clearly define a background level. The column density at the map borders is on the order of a few Av, but may still contain parts of the associated molecular cloud.

Figure 3 (left) shows the column density map and the corresponding PDF (right). The PDF has a complex structure, and the best results (we performed KS-tests for which we fit different distributions) were obtained with two lognormal distributions in the lower column density range and one power-law tail for higher column densities. The widths of the lognormal forms are $\sigma$=0.18 for both, and the peaks are around Av = 7 and Av = 11. Starting at Av = 20, the distribution is better described by a power-law tail with a slope of s=–2.46, which corresponds to $\alpha$=1.8 for a spherical density distribution with $\rho\propto r^{-\alpha}$. Our interpretation of these results is that the first lognormal form shows the turbulent gas of the associated molecular cloud (in dark blue scale in the column density map), followed by the compressed shell component (indicated by the gas component between the light blue and black contours in Fig. 3). This turbulent gas layer starts to fragment, and gravity takes over in the densest parts of the compressed shell, forming clumps and finally cores. The gravitational collapse of the embedded cores then leads to the power-law tail. The exponent $\alpha$=1.8 assuming a spherical density distribution is consistent with the exponent $\alpha$=1.5–2 predicted from theory (Shu 1977; Whitworth & Summers 1985). These results are fully consistent with what is found in Tremblin et al. (2014b) for RCW 120, which is also an H ii region bubble. The only difference is that the peaks of the two lognormal distributions of the unperturbed lower density gas and the compressed shell are closer together, implying that the density contrast in RCW 79 is lower. The second lognormal form indicates the compression from ionized gas that might have created the necessary condition for triggered star formation in RCW 79.

4.3 Compact sources

4.3.1 Source extraction

The algorithm getsources (Men’shchikov et al. 2010, 2012; Men’shchikov 2013) was used to extract compact sources from the images at all Herschel wavelengths from 70 to 500 $\mu$m. Full details on the source extraction can be found in Appendix A.1. The resulting catalog returned by getsources contains the identity number of sources, unique coordinates, peak and integrated fluxes with respective errors, and FWHM major and minor sizes with a position angle at each wavelength, as presented in Table B. In our work, 317 sources were initially extracted as candidate compact sources (Sigmono $\geq 7$)888Sigmono is the detection significance given by getsources. A source with Sigmono $\geq 7$ is regarded as reliable (Men’shchikov et al. 2012). within a region of 25$\arcmin\times$ 25$\arcmin$ centered at $\alpha_{2000}=13^{\mathrm{h}}40^{\mathrm{m}}20\aas@@fstack{s}928,\ \delta_{2000}=-61\degr 42\arcmin 20\aas@@fstack{\prime\prime}16$.

To pick out the most reliable compact sources, two selection criteria were applied to the 317 sources:

A minimum of three measured integrated fluxes with good qualities for a better constraint on the SED fitting in Sect. 4.3.2. They must include the flux at a reference wavelength (160 or 250 $\mu$m, see Sect.A.2). The signal-to-noise (S/N) ratios of the integrated and corresponding peak fluxes at each wavelength have to be greater than 2 to guarantee the good qualities of the flux measurements. 2. 2.

An axis ratio of $<2$ and a deconvolved size (see Eq. 4) of $<0.4$ pc for preliminarily selected compact sources. The latter is arbitrarily determined and is based on the fact that most of sources in the catalog have sizes of $<0.4$ pc. Objects that do not fulfill the above criteria may be cloud fragments or filament pieces.

Applying these criteria, we end up with a sample of 100 candidate compact sources.

4.3.2 Graybody SED fitting

Assuming optically thin dust emission, we adopted a single-temperature graybody function to fit the SED of sources between 100 and 500 $\mu$m (see Appendix A.2). The SED fitting was performed for the 100 candidate compact sources to derive their physical parameters including the dust temperature $T_{\rm d}$ and envelope mass $M_{\rm env}$. As mentioned in Sect 4.1, 70 $\mu$m emission was not included in the SED fitting. Before the SED fitting, we scaled fluxes to the same aperture at the reference wavelength (see Sect. A.2) and made the corresponding color corrections. Detailed descriptions of the flux scaling and color correction methods can be found in Appendix A.2. In the SED fitting, the dust emissivity spectral index, $\beta$, was set at 2 and was not left as a free parameter. This is the value adopted for the analysis of the HOBYS survey. Moreover, Men’shchikov (2016) suggested that variable $\beta$ during the SED fitting for mass derivation leads to huge biases and should never be used (Men’shchikov 2016). We must keep in mind that absolute values in masses are at least a factor of 2–3 (Men’shchikov 2016). After the SED fitting, we kept 89 sources selected by the goodness of their fit ($\chi^{2}/N_{data}<10$).

4.3.3 Infrared counterparts

We searched for the possible IR features of the 89 sources in the 1.25 to 70 $\mu$m range, including point-like objects, absorption against local bright background emission, and filament- or extended-structure emission. A point-like object, with a size of $<10\arcsec$ depending on the resolution of the IR data (see Sect. 3), may be an indicator of ongoing star formation, absorption is indicative of cold gas lying in front of the hot dust, and the IR filament or extended-structure implies an accumulation of either hot dust or PDRs in which there may be embedded point-like objects that are not easily separated from bright background emission.

Taking advantage of Herschel images complemented with the $18\aas@@fstack{\prime\prime}2$ resolution column density map and other IR data, we made a plot consisting of 16 $1\aas@@fstack{\prime}5\times 1\aas@@fstack{\prime}5$ images for each source (see Fig. 14) to pinpoint the IR counterparts. The IR sources were searched for within 5$\arcsec$, which corresponds to 0.1 pc at the distance of RCW 79.

Following the appearance of their infrared emission, we classified the sources into three groups:

$Group\,0$ compact sources with IR absorption or without any detectable IR counterparts, 2. 2.

$Group\,IM$ (i.e., intermediate) compact sources with filament or extended-structure IR emission, 3. 3.

$Group\,I$ compact sources with point-like IR counterparts.

By visually inspecting the plots in Fig. 14, we identified 14 $Group\,0$ and 11 $Group\,I$ sources. The remaining 64 out of 89 sources are found to be only spatially coincident with filament (or extended) emission. These sources can be either compact sources or pieces of clouds. To distinguish the compact sources from the pieces of clouds, we requested that the compact sources have at least three good flux measurements at wavelengths $\geq 100$ $\mu$m. The good photometry at each wavelength is defined by the photometry ellipse centered on the corresponding density peak. For example, the photometry ellipses of source 1 at wavelengths 100 to 500 $\mu$m are centered on the respective density peaks (see Fig. 14). As a result, we picked out 25 $Group\,IM$ sources. In all, we obtained 14 $Group\,0$, 25 $Group\,IM$, and 11 $Group\,I$ compact sources. The physical parameters of these 50 compact sources are summarized in Cols. 1-6 of Table 4.3.4, including the ID, the coordinates ($R.A.$ and $Dec.$), the deconvolved size ($D_{\rm dec}$), the dust temperature ($T_{\rm d}$), the envelope mass ($M_{\rm env}$), and the number density ($n_{{}_{\rm H_{2}}}$). The errors of $T_{\rm d}$ and $M_{\rm env}$, given by the MPFITFUN999http://cow.physics.wisc.edu/~craigm/idl/mpfittut.html procedure, mainly arise from the photometric flux error at each wavelength (see Table B). The 50 compact sources have sizes ranging from 0.1 to 0.4 pc with an average value of 0.2 pc, temperatures ranging from 11 to 26 K, envelope masses ranging from 6 to 760 $M_{\odot}$, and number density ranging from 0.1 to $44\times 10^{5}$ cm*-3*. In the following, we should keep in mind that due to their large typical size of 0.2 pc, these compact sources may be made of different sources in different evolutionary stages.

Figure 4 displays the spatial distribution of the 50 compact sources overlaid on the high-resolution column density map. They are predominantly concentrated on the local density peaks, which has also been observed in other star-forming regions like the Rosette molecular cloud (Schneider et al. 2012). Interestingly, $96\%$ of the sources are observed toward the compressed layer (within the black contour in Fig. 4, see Sect. 4.2). This distribution not only indicates that these compact sources are exposed to the influence of the H ii region, but it is also suggestive of more efficient formation of compact sources in the layer of compressed gas than in other regions away from the H ii region. Moreover, 26 out of 50 compact sources are found to be associated with the gravitationally bound gas (within the white contour). Coupled with their associated IR counterparts, the 26 compact sources have a high probability of forming stars through gravitational collapse.

4.3.4 Luminosity

The bolometric luminosities $L_{\rm bol}$ for the 50 compact sources are calculated as

[TABLE]

The bolometric luminosity of the 39 $Group\,0$ and $Group\,IM$ sources that have no IR point-like objects was obtained by integrating the graybody SED fits over frequencies. For the 11 $Group\,I$ sources, IR fluxes were added to the calculation. To obtain the IR fluxes, we cross matched these 11 sources with those in the archival GLIMPSE I (Benjamin et al. 2003), MIPSGAL (Gutermuth & Heyer 2015), and ALLWISE (Wright et al. 2010) catalogs within a search radius of $5\arcsec$. These catalogs all have been cross matched with the 2MASS survey. Therefore, if there is any, the near IR fluxes can be simultaneously retrieved. All $Group\,I$ sources except for source 28 can be well matched in the catalogs. For source 28 we used the software DS9 to perform aperture photometries at the wavelengths where the IR counterpart exists. Table B gives a summary of the resulting IR fluxes for the 11 compact sources. In addition, the submillimeter luminosities ($L_{{}_{\rm submm}}^{{}_{\lambda>\rm 350}}$) for all 50 compact sources were derived from the integrated luminosity of the resulting SED fit over wavelengths $\geq 350$ $\mu$m. The derived $L_{\rm bol}$ and $L_{{}_{\rm submm}}^{{}_{\lambda>\rm 350}}$ are given in Table 4.3.4. An uncertainty of $10\%$ for both $L_{\rm bol}$ and $L_{{}_{\rm submm}}^{{}_{\lambda>\rm 350}}$ is estimated from the flux errors. The bolometric luminosities of the 50 compact sources range from 19 to 12712 $L_{\odot}$.