J/ApJ/764/L19 Methanol emission from the Galactic Center (Yusef-Zadeh+, 2013)
Widespread methanol emission from the Galactic Center: the role of cosmic rays.
Yusef-Zadeh F., Cotton W., Viti S., Wardle M., Royster M.
<Astrophys. J., 764, L19 (2013)>
=2013ApJ...764L..19Y 2013ApJ...764L..19Y
ADC_Keywords: Radio continuum ; Masers ; Milky Way
Keywords: astrochemistry; cosmic rays; Galaxy: nucleus; ISM: molecules; masers;
stars: early-type
Abstract:
We report the discovery of a widespread population of collisionally
excited methanol J=4-1 to 30E sources at 36.2GHz from the inner
66'x18' (160x43pc) of the Galactic center. This spectral feature was
imaged with a spectral resolution of 16.6km/s taken from 41 channels
of a Very Large Array continuum survey of the Galactic center region.
The revelation of 356 methanol sources, most of which are maser
candidates, suggests a large abundance of methanol in the gas phase in
the Galactic center region. There is also spatial and kinematic
correlation between SiO (2-1) and CH3OH emission from four Galactic
center clouds: the +50 and +20km/s clouds and G0.13-0.13 and
G0.25+0.01. The enhanced abundance of methanol is accounted for in
terms of induced photodesorption by cosmic rays as they travel through
a molecular core, collide, dissociate, ionize, and excite Lyman Werner
transitions of H2. A time-dependent chemical model in which cosmic
rays drive the chemistry of the gas predicts CH3OH abundance of
10-8 to 10-7 on a chemical timescale of 5x104 to 5x105 years.
The average methanol abundance produced by the release of methanol
from grain surfaces is consistent with the available data.
Description:
Observations were made in six sessions between 2012 February 21 and
March 10 with the K. Jansky Very Large Array of the National Radio
Astronomy Observatory (NRAO) in its C configuration as part of a
continuum survey (centered at 36.169265GHz).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 77 355 Detected CH3OH sources in the survey
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See also:
J/A+A/563/A68 : CH3OH and H2O Galactic center masers (Chambers+, 2014)
J/ApJ/702/178 : YSOs in the central 400pc of the Galaxy (Yusef-Zadeh+, 2009)
J/ApJ/699/186 : VLA observations of the Galactic center (Zhao+, 2009)
J/ApJS/155/421 : Survey of Galactic Center region at 20cm (Yusef-Zadeh+, 2004)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- Seq [1/355] Running sequence number of the source
5- 13 F9.5 deg GLON Galactic longitude
15- 22 F8.5 deg GLAT Galactic latitude
24- 29 F6.2 Jy.km/s Flux [0.1/469] Observed line flux (at 36.2GHz)
31- 36 F6.1 km/s Vel [-183/266] Velocity
38- 44 F7.2 cK Tb [7.4/7261] Brightness temperature (°Kx100)
46- 51 F6.2 cK e_Tb Uncertainty in Tb (°Kx100)
53- 56 F4.2 arcsec amaj [0.7/6] Major size fit
58- 61 F4.2 arcsec amin [0.07/6] Minor size fit
63- 68 F6.1 deg PA [-309/354] Position angle of fitted ellipse
70- 77 A8 --- Ref "SPF 2010": Sjouwerman+, 2010ApJ...710L.111S 2010ApJ...710L.111S
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 28-Oct-2014