Bibcode
Martín-Hernández, N. L.; Bik, A.; Puga, E.; Nürnberger, D. E. A.; Bronfman, L.
Referencia bibliográfica
Astronomy and Astrophysics, Volume 489, Issue 1, 2008, pp.229-243
Fecha de publicación:
10
2008
Revista
Número de citas
20
Número de citas referidas
20
Descripción
Aims: IRAS 19410+2336 is a young massive star forming region with an
intense outflow activity. Outflows are frequently studied in the
near-infrared (NIR) since the H2 emission in this wavelength range often
traces the shocked molecular gas. However, the mechanisms behind the H2
emission detected in IRAS 19410+2336 have not been clarified yet. We
present here spatially resolved NIR spectroscopy which allows us to
verify whether the H2 emission 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). Methods: We
obtained long-slit, intermediate-resolution, NIR spectra of IRAS
19410+2336 using LIRIS, the NIR imager/spectrographer mounted on the 4.2
m William Herschel Telescope. As a complement, we also obtained J, H and
Ks images with the Las Campanas 2.5 m Du Pont Telescope, and
archival mid-infrared (MIR) Spitzer images at 3.6, 4.5, 5.8 and 8.0
μm. Results: We confirm the shocked nature of the H2 emission,
with an excitation temperature of about 2000 K, based on the analysis of
relevant H2 line ratios, ortho-to-para ratios and excitation diagrams.
We have also identified objects with very different properties and
evolutionary stages in IRAS 19410+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 -
probably coming through a cavity created by one of the outflows present
in the region, or from the outflow cavity itself - is leaking at these
wavelengths. The second most massive millimeter source, mm2, is only
detected at λ ⪆ 6 μm, 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.
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