The Ap 2-1 nebula and the surrounding molecular cloud G35.2-0.74: an active star forming region

TL;DR

This study uses multiwavelength data to analyze the star-forming activity and properties of the Ap 2-1 nebula and surrounding molecular cloud G35.2-0.74, confirming active star formation and the nebula's embedded nature.

Contribution

It provides a detailed multiwavelength analysis of the Ap 2-1 nebula and molecular cloud, confirming the nebula's distance, star formation activity, and likely excitation source.

Findings

The Ap 2-1 nebula is embedded in the molecular cloud at ~2 kpc.

Active star formation is confirmed with a young stellar object cluster.

The nebula is likely excited by an early B-type star.

Abstract

Using data from large-scale surveys: 2MASS, GLIMPSE, MIPSGAL, VGPS, GRS, and IPHAS, we performed a multiwavelength study of the ISM in a region of about 20' x 20' towards the molecular cloud G35.2-0.74. Additionally, the Ap 2-1 nebula, that is seen in projection over the molecular cloud, was studied using optical data obtained with the 2.15 m telescope at CASLEO, Argentina. From the HI absorption study we estimate a distance of ~2 kpc for Ap 2-1 confirming that the nebula is embedded in the south portion of the molecular cloud G35.2-0.74. Performing a photometric study and analysing the spectral energy distributions of the sources likely embedded in the cloud, we confirm that this region is very active in star formation, mainly towards the north, where we discover a cluster of young stellar objects. From the H_alpha and [NII] lines we obtain a radial velocity of v_LSR ~ 31 km/s for the Ap 2-1 nebula, in coincidence with the velocity of the molecular cloud. Finally, we conclude that Ap 2-1 is an HII region probably excited by an early B-type star.