J/MNRAS/416/2 Photodissociation regions in M33 (Heiner+, 2011)
Atomic hydrogen produced in M33 photodissociation regions.
Heiner J.S., Allen R.J., Van Der Kruit P.C.
<Mon. Not. R. Astron. Soc., 416, 2-12 (2011)>
=2011MNRAS.416....2H 2011MNRAS.416....2H
ADC_Keywords: Galaxies, nearby ; Molecular clouds ; H I data ; Ultraviolet
Keywords: ISM: atoms - ISM: clouds - ISM: molecules -
galaxies: individual: M33 - galaxies: ISM - ultraviolet: galaxies
Abstract:
We derive total (atomic + molecular) hydrogen densities in giant
molecular clouds (GMCs) in the nearby spiral galaxy M33 using a method
that views the atomic hydrogen near regions of recent star formation
as the product of photodissociation. Far-ultraviolet (FUV) photons
emanating from a nearby OB association produce a layer of atomic
hydrogen on the surfaces of nearby GMCs. Our approach provides an
estimate of the total hydrogen density in these GMCs from observations
of the excess FUV emission that reaches the GMC from the OB
association and of the excess 21-cm radio HI emission produced after
these FUV photons convert H2 into HI on the GMC surface. The method
provides an alternative approach to the use of CO emission as a tracer
of H2 in GMCs and is especially sensitive to a range of densities well
below the critical density for CO(1-0) emission.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table5.dat 43 42 Locations and FUV fluxes of candidate
photodissociation regions (PDRs)
table6.dat 34 208 Candidate photodissociation regions results
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Byte-by-byte Description of file: table5.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- Seq [1/42] Source sequential number
4 I1 h RAh Right ascension (J2000)
6- 7 I2 min RAm Right ascension (J2000)
9- 14 F6.3 s RAs Right ascension (J2000)
16 A1 --- DE- Declination sign (J2000)
17- 18 I2 deg DEd Declination (J2000)
20- 21 I2 arcmin DEm Declination (J2000)
23- 27 F5.2 arcsec DEs Declination (J2000)
29- 32 F4.2 kpc Rad Radius (distance from M33 galaxy center)
34- 39 F6.2 10-17W/m2/nm FFUV Far-UV flux (in 10-15erg/cm2/s/Å)
41- 43 I3 arcsec Ap [36/180] Aperture
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Byte-by-byte Description of file: table6.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- Seq [1/42] Source sequential number
3 A1 --- m_Seq [a-h] Multiplicity index on Seq
5- 7 I3 pc rho(HI) Separation between the OB clusters and
associated HI patches
9- 12 F4.2 10+21cm-2 NHI HI column density
14- 18 F5.3 --- G0 Incident flux G0
19- 24 F6.2 --- G/Gbg Source contrast
26- 29 I4 cm-3 nH Total hydrogen volume density
31- 34 F4.2 --- e_nH [0,1] Fractional error on nH
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 02-Mar-2012