J/ApJ/723/1019 Galactic SFR and gas surface densities (Heiderman+, 2010)
The star formation rate and gas surface density relation in the Milky Way: implications for extragalactic studies. Heiderman A., Evans II N.J., Allen L.E., Huard T., Heyer M. <Astrophys. J., 723, 1019-1037 (2010)> =2010ApJ...723.1019H
ADC_Keywords: Molecular clouds ; Extinction ; Interstellar medium ; Milky Way ; YSOs Keywords: dust, extinction - galaxies: ISM - galaxies: star formation - infrared: stars - ISM: clouds - stars: formation Abstract: We investigate the relation between star formation rate (SFR) and gas surface densities in Galactic star-forming regions using a sample of young stellar objects (YSOs) and massive dense clumps. Our YSO sample consists of objects located in 20 large molecular clouds from the Spitzer cores to disks (c2d; Evans, 2009, Cat. J/ApJS/181/321) and Gould's Belt (GB) survey (L. Allen et al. 2010, in preparation). These data allow us to probe the regime of low-mass star formation, essentially invisible to tracers of high-mass star formation used to establish extragalactic SFR-gas relations. We estimate the gas surface density (Σgas) from extinction (AV) maps and YSO SFR surface densities (ΣSFR) from the number of YSOs, assuming a mean mass and lifetime. We also divide the clouds into evenly spaced contour levels of AV, counting only Class I and Flat spectral energy distribution YSOs, which have not yet migrated from their birthplace. For a sample of massive star-forming clumps, we derive SFRs from the total infrared luminosity and use HCN gas maps to estimate gas surface densities. We find that c2d and GB clouds lie above the extragalactic SFR-gas relations (e.g., Kennicutt-Schmidt law) by factors of up to 17. We use 12CO and 13CO gas maps of the Perseus and Ophiuchus clouds from the COMPLETE survey (Ridge et al. 2006AJ....131.2921R) to estimate gas surface densities and compare to measurements from AV maps. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 96 21 Measured quantities for clouds table3.dat 103 100 Properties of suspicious YSOs and MISFITS (misidentified YSOs from SED FITS) for 13 clouds
See also: J/A+A/515/A42 : Catalog of high extinction clouds (Rygl+, 2010) J/ApJ/715/310 : Early stages of star formation in IRDCs (Rathborne+, 2010) J/ApJS/181/321 : Properties of Spitzer c2d dark clouds (Evans+, 2009) J/ApJ/699/1092 : Giant molecular clouds (SRBY) (Heyer+, 2009) J/ApJS/185/198 : The Cepheus flare observed with IRAC and MIPS (Kirk+, 2009) J/ApJ/698/324 : Spitzer IRDCs (Ragan+, 2009) J/A+A/487/993 : MAMBO Mapping of c2d Clouds and Cores (Kauffmann+, 2008) J/ApJ/680/1295 : Optical spectroscopy of Cha-II PMS stars (Spezzi+, 2008) J/ApJ/680/495 : Interstellar clouds in the Gould belt (Harvey+, 2008) J/ApJ/683/822 : Star formation in Ophiuchus and Perseus II. (Jorgensen+, 2008) J/ApJS/177/551 : Spitzer c2d survey of Lupus dark clouds (Merin+, 2008) J/ApJ/663/1149 : Spitzer survey of Serpens YSO population (Harvey+, 2007) J/A+A/468/1009 : Star formation in Perseus. II. (Hatchell+, 2007) J/ApJ/551/852 : FCRAO CO survey of the outer Galaxy (Heyer+, 2001) Byte-by-byte Description of file: table1.dat
Bytes Format Units Label Explanations
1- 9 A9 --- Cloud Cloud name 10 A1 --- n_Cloud [*] *: data from litterature 12- 15 I4 --- Ntot Total number of YSOs above AV=2 (1) 17- 19 I3 --- NI ? Number of Class I objects above AV=2 (1) 21- 22 I2 --- NF ? Number of Flat SED objects >AV=2 (1) 24- 26 I3 pc Dist Distance to cloud 28- 29 I2 pc e_Dist ? Dist uncertainty 31- 36 F6.3 deg2 Omega Solid angle (angular area Ω) of cloud 38- 43 F6.2 pc2 Area Cloud area 45- 49 F5.2 pc2 e_Area ? Area uncertainty 51- 55 I5 Msun Mass Mass of cloud (gas) 57- 60 I4 Msun e_Mass ? Mass uncertainty 62- 66 F5.1 Msun/pc2 Sigma Surface gas density Σgas 68- 69 I2 Msun/pc2 e_Sigma ? Sigma uncertainty 71- 76 F6.2 Msun/Myr SFR Star formation rate 78- 83 F6.2 Msun/Myr e_SFR ? SFR uncertainty 85- 90 F6.4 Msun/yr/kpc2 SigSFR SFR density ΣSFR 92- 96 F5.3 Msun/yr/kpc2 e_SigSFR ? SigSFR uncertainty
Note (1): Total AV mass from Pineda et al. (2010ApJ...721..686P) and YSO data from Rebull et al. (2010ApJS..186..259R).
Byte-by-byte Description of file: table3.dat
Bytes Format Units Label Explanations
1- 8 A8 --- Cloud Cloud name 10- 11 I2 h RAh Hour of right ascension (J2000) 13- 14 I2 min RAm Minute of right ascension (J2000) 16- 20 F5.2 s RAs Second of right ascension (J2000) 22 A1 --- DE- Sign of declination (J2000) 23- 24 I2 deg DEd Degree of declination (J2000) 26- 27 I2 arcmin DEm Arcminute of declination (J2000) 29- 33 F5.2 arcsec DEs Arcsecond of declination (J2000) 35- 53 A19 --- Class Spitzer classification (see Evans et al. 2009; Cat. J/ApJS/181/321) 55- 59 F5.2 --- alpha Spectral Index, extinction corrected values for c2d clouds only 61- 64 F4.2 K.km/s MBdV ? Integrated main beam HCO+line intensity 66- 69 F4.2 K.km/s e_MBdV ? MBdV uncertainty 71 A1 --- l_TMB Limit flag on TMB, upper limits are computed as 2σrms 72- 75 F4.2 K TMB Main beam HCO+ line temperature 77- 80 F4.2 K e_TMB ? TMB uncertainty 82- 85 A4 --- SED SED class based on Greene et al. (1994ApJ...434..614G) 87 A1 --- l_AV Limit flag on AV (1) 88- 89 I2 mag AV AV at source position 91-103 A13 --- Comm Line profile comments
Note (1): Values that are found outside the AV map completeness limit are given as < limit.
History: From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 24-Jul-2012
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