J/MNRAS/492/1335 Star formation and 6.7GHz methanol masers (Paulson+, 2020)
Probing the early phases of high-mass star formation with 6.7GHz methanol
masers.
Paulson S.T., Pandian J.D.
<Mon. Not. R. Astron. Soc., 492, 1335-1347 (2020)>
=2020MNRAS.492.1335P 2020MNRAS.492.1335P (SIMBAD/NED BibCode)
ADC_Keywords: Masers ; Star Forming Region ; Millimetric/submm sources
Keywords: masers - techniques: photometric - stars: formation
Abstract:
Methanol masers at 6.7GHz are the brightest of class II methanol
masers and have been found exclusively towards massive star-forming
regions. These masers can thus be used as a unique tool to probe the
early phases of massive star formation. We present here a study of the
spectral energy distributions of 320 6.7GHz methanol masers chosen
from the Methanol Multibeam catalogue, which fall in the Hi-GAL range
(|l|=<60°, |b|=<1°). The spectral energy distributions are
constructed from 870 to 70µm using data from the ATLASGAL and
Hi-GAL surveys. The emission from cold dust is modelled by a single
grey body component fit. We estimate the clump properties such as
mass, far-infrared luminosity, and column density using the
best-fitting parameters of the SED fits. Considering the Kauffman
criteria for massive star formation, we find that all but a few maser
hosts have the potential to harbour at least one high-mass star. The
physical properties of the methanol maser hosts are also discussed.
The evolutionary stages of 6.7GHz maser sources, explored using the
mass luminosity diagram, suggest that they are predominantly
associated with high-mass stars with the majority being in the
accretion phase. However, we observe a small number of sources that
could possibly be related to intermediate- or low-mass stars.
Description:
Our methanol maser sample has been selected from the catalogue of the
MMB survey. The MMB survey covers the entire Galactic plane with a
latitude coverage of |b|=<2° and the catalogue comprises of a
total of 972 sources. We have restricted our analysis to sources that
have been covered by the Hi-GAL survey (|l|=<60°, |b|=<1°).
This limits the number of masers in our sample to 630. Determination
of physical parameters such as mass, size, and luminosity of the
sources requires knowledge of the distances to the sources; and this
brings the sample size to 602 sources. The distances are taken from
Urquhart et al. (2013MNRAS.431.1752U 2013MNRAS.431.1752U, Cat. J/MNRAS/431/1752), Reid et
al. (2014ApJ...783..130R 2014ApJ...783..130R, Cat. J/ApJ/783/130), Pandian, Menten &
Goldsmith (2009ApJ...706.1609P 2009ApJ...706.1609P), and Green et al.
(2017MNRAS.469.1383G 2017MNRAS.469.1383G).
We have discarded sources that are either saturated in the Hi-GAL data
or are in very crowded fields where reliable photometry is difficult.
We have also taken into account only sources that have ATLASGAL
counterparts. This gave a final methanol maser sample of 320 sources
among which the integrated flux densities of 311 methanol maser
sources are taken from Breen et al. (2015MNRAS.450.4109B 2015MNRAS.450.4109B).
Fluxes from 870 to 70µm have been determined from aperture
photometry of the ATLASGAL and Hi-GAL images (level 2.5 images in the
Herschel archive). The 870µm ATLASGAL data have a resolution of
19arcsec, while the Hi-GAL data have a resolution of 36.9, 25.3, 18.0,
11.6, and 10.2arcsec at 500, 350, 250, 160, and 70µm, respectively.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 79 320 Flux densities of sources hosting 6.7GHz
methanol masers from 870 to 70µm
table2.dat 46 320 The best-fitting parameters of characteristic
sources
table3.dat 53 320 The physical properties derived from
best-fitting parameters of characteristic
sources
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See also:
J/MNRAS/431/1752 : ATLASGAL 6.7GHz methanol masers (Urquhart+, 2013)
J/ApJ/783/130 : Parallaxes of high mass star forming regions (Reid+, 2014)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 14 A14 --- Name Source name (GLLL.lll+B.bbb)
16- 20 F5.2 Jy S870 Flux density at 870um
22- 25 F4.2 Jy e_S870 Error on S870
27- 32 F6.2 Jy S500 Flux density at 500um
34- 38 F5.2 Jy e_S500 Error on S500
40- 45 F6.2 Jy S350 Flux density at 350um
47- 51 F5.2 Jy e_S350 Error on S350
53- 58 F6.2 Jy S250 Flux density at 250um
60- 64 F5.2 Jy e_S250 Error on S250
66- 72 F7.2 Jy S160 Flux density at 160um
74- 79 F6.2 Jy e_S160 Error on S160
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 14 A14 --- Name Source name (GLLL.lll+B.bbb)
16- 20 F5.2 kpc Dist Distance
22- 26 F5.2 K Tc Temperature of the cold dust component
28- 35 E8.2 sr Omegac Solid angle of cold dust as seen in aperture
photometry
37- 41 F5.3 --- tau Optical depth of dust at 500um
43- 46 F4.2 --- beta Dust spectral index
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 14 A14 --- Name Source name (GLLL.lll+B.bbb)
16- 23 E8.2 Msun Mass Clump mass
25- 32 E8.2 cm-2 NH2 Hydrogen column density
34- 38 F5.3 pc Rad ? Effective radius (1)
40- 44 F5.3 g/cm2 Sigma ? Surface density (1)
46- 53 E8.2 Lsun LFIR FIR luminosity
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Note (1): We have not provided the radius and surface density values of sources
that weren't properly resolved
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History:
From electronic version of the journal
(End) Ana Fiallos [CDS] 14-Mar-2023