Spatially resolved near-infrared spectroscopy of the massive star-forming region IRAS 19410+2336

TL;DR

This study uses spatially resolved near-infrared spectroscopy to analyze the excitation mechanisms, environmental conditions, and evolutionary stages of sources within the massive star-forming region IRAS 19410+2336.

Contribution

It provides the first spatially resolved NIR spectroscopic analysis of IRAS 19410+2336, confirming shock-excited H2 emission and identifying different evolutionary stages of embedded sources.

Findings

H2 emission is shock-excited with an excitation temperature of about 2000 K.

The most massive millimeter source, mm1, has a bright NIR and MIR counterpart.

The less evolved source, mm2, is detected only at wavelengths >6 μm, indicating a high-mass protostar in accretion.

Abstract

IRAS19410+2336 is a young massive star forming region with an intense outflow activity. We present here spatially resolved NIR spectroscopy which allows us to verify whether the H2 emission detected in this object originates from thermal emission in shock fronts or from fluorescence excitation by non-ionizing UV photons. Moreover, NIR spectroscopy also offers the possibility of studying the characteristics of the putative driving source(s) of the H2 emission by the detection of photospheric and circumstellar spectral features, and of the environmental conditions (e.g. extinction). We obtained long-slit, intermediate-resolution, NIR spectra of IRAS19410+2336 using LIRIS. As a complement, we also obtained J, H and K_s images with the Las Campanas 2.5m Du Pont Telescope, and archival mid-infrared (MIR) Spitzer images at 3.6, 4.5, 5.8 and 8.0 um. We confirm the shocked nature of the H2 emission, with an excitation temperature of about 2000 K. We have also identified objects with very different properties and evolutionary stages in IRAS19410+2336. The most massive source at millimeter wavelengths, mm1, with a mass of a few tens of solar masses, has a bright NIR (and MIR) counterpart. This suggests that emission is leaking at these wavelengths. The second most massive millimeter source, mm2, is only detected at lambda > 6 um, suggesting that it could be a high-mass protostar still in its main accretion phase. The NIR spectra of some neighboring sources show CO first-overtone bandhead emission which is associated with neutral material located in the inner regions of the circumstellar environment of YSOs.