J/MNRAS/454/4335 Multiwavelength photometry of Sh 2-138 YSOs (Baug+, 2015)
Sh 2-138: physical environment around a small cluster of massive stars.
Baug T., Ojha D.K., Dewangan L.K., Ninan J.P., Bhatt B.C., Ghosh S.K.,
Mallick K.K.
<Mon. Not. R. Astron. Soc., 454, 4335-4356 (2015)>
=2015MNRAS.454.4335B 2015MNRAS.454.4335B (SIMBAD/NED BibCode)
ADC_Keywords: H II regions ; YSOs ; Photometry
Keywords: stars: formation - HII regions - ISM: individual objects: Sh 2-138 -
infrared: ISM - radio continuum: ISM
Abstract:
We present a multiwavelength study of the Sh 2-138, a Galactic compact
HII region. The data comprise of optical and near-infrared (NIR)
photometric and spectroscopic observations from the 2-m Himalayan
Chandra Telescope, radio observations from the Giant Metrewave Radio
Telescope (GMRT), and archival data covering radio through NIR
wavelengths. A total of 10 Class I and 54 Class II young stellar
objects (YSOs) are identified in a 4.6-arcminx4.6-arcmin area of the
Sh 2-138 region. Five compact ionized clumps, with four lacking of any
optical or NIR counterparts, are identified using the 1280MHz radio
map, and correspond to sources with spectral type earlier than B0.5.
Free-free emission spectral energy distribution fitting of the central
compact HII region yields an electron density of ∼2250±400cm-3.
With the aid of a wide range of spectra, from 0.5-15µm, the central
brightest source - previously hypothesized to be the main ionizing
source - is characterized as a Herbig Be type star. At large scale
(15-arcminx15-arcmin), the Herschel images (70-500µm) and the
nearest neighbour analysis of YSOs suggest the formation of an
isolated cluster at the junction of filaments. Furthermore, using a
greybody fit to the dust spectrum, the cluster is found to be
associated with the highest column density (∼3x1022cm-2) and high
temperature (∼35K) regime, as well as with the radio continuum
emission. The mass of the central clump seen in the column density map
is estimated to be ∼3770M☉.
Description:
Optical BVRI imaging observations of the Sh2-138 region were carried
out on 2005 September 8 using the Himalaya Faint Object Spectrograph
and Camera (HFOSC) mounted on the 2 m Himalayan Chandra Telescope
(HCT).
In order to identify strong Hα emission sources in the Sh2-138
region, slitless Hα spectra were obtained using the HFOSC on
2007 November 16.
Optical spectroscopic observations of the central brightest source
were performed using the HFOSC on 2014 November 18.
The newly installed TIFR Near Infrared Spectrometer and Imager Camera
(TIRSPEC) on the HCT was used for NIR observations on 2014 November 18
under photometric conditions with an average seeing of 1.4 arcsec.
We obtained NIR spectra of the central brightest source on 2014 May
29, using the TIRSPEC, in NIR Y (1.02-1.20um), J (1.21-1.48um),
H (1.49-1.78um), and K (2.04-2.35um) bands. We conducted optical
narrow-band imaging observations of the region in Hα filter
(λ∼6563Å, Δλ∼100Å) with exposure
times of 600s, 250s, and 50s on 2005 September 8 using the HFOSC.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tables1.dat 178 151 Catalog of YSOs towards the Sh 2-138 region
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Byte-by-byte Description of file: tables1.dat
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Bytes Format Units Label Explanations
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1- 2 I2 h RAh Right ascension (J2000.0)
4- 5 I2 min RAm Right ascension (J2000.0)
7- 12 F6.3 s RAs Right ascension (J2000.0)
13 A1 --- DE- Declination sign (J2000.0)
14- 15 I2 deg DEd Declination (J2000.0)
17- 18 I2 arcmin DEm Declination (J2000.0)
20- 25 F6.3 arcsec DEs Declination (J2000.0)
27- 32 F6.3 mag Bmag ?=- Johnson B magnitude
34- 38 F5.3 mag e_Bmag ? rms uncertainty on Bmag
40- 45 F6.3 mag Vmag ?=- Johnson V magnitude
47- 51 F5.3 mag e_Vmag ? rms uncertainty on Vmag
53- 58 F6.3 mag Rmag ?=- Cousins R magnitude
60- 64 F5.3 mag e_Rmag ? rms uncertainty on Rmag
66- 71 F6.3 mag Imag ?=- Cousins I magnitude
73- 77 F5.3 mag e_Imag ? rms uncertainty on Imag
79- 84 F6.3 mag Jmag ?=- TIRSPEC J magnitude
86- 90 F5.3 mag e_Jmag ? rms uncertainty on Jmag
92- 97 F6.3 mag Hmag ?=- TIRSPEC H magnitude
99-103 F5.3 mag e_Hmag ? rms uncertainty on Hmag
105-110 F6.3 mag Ksmag ?=- TIRSPEC Ks magnitude
112-116 F5.3 mag e_Ksmag ? rms uncertainty on Ksmag
118-123 F6.3 mag W1mag ?=- WISE W1 magnitude
125-129 F5.3 mag e_W1mag ? rms uncertainty on W1mag
131-136 F6.3 mag W2mag ?=- WISE W2 magnitude
138-142 F5.3 mag e_W2mag ? rms uncertainty on W2mag
144-149 F6.3 mag W3mag ?=- WISE W3 magnitude
151-155 F5.3 mag e_W3mag ? rms uncertainty on W3mag
157-162 F6.3 mag W4mag ?=- WISE W4 magnitude
164-168 F5.3 mag e_W4mag ? rms uncertainty on W4mag
170-178 A9 --- Type Source Type
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 22-Jul-2016