J/ApJ/805/31 IR-radio luminosities & surface densities of galaxies (Liu+, 2015)
The global star formation laws of galaxies from a radio continuum perspective.
Liu L., Gao Y., Greve T.R.
<Astrophys. J., 805, 31 (2015)>
=2015ApJ...805...31L 2015ApJ...805...31L (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, nearby ; Radio continuum ; Galaxies, IR
Keywords: galaxies: evolution; galaxies: ISM; galaxies: spiral;
galaxies: starburst; stars: formation
Abstract:
We study the global star formation law --the relation between gas and
star formation (SF) rates-- in a sample of 181 local galaxies with
infrared (IR) luminosities spanning almost five orders of magnitude
(107.8-1012.3L☉), which includes 115 normal spiral galaxies
and 66 (ultra)luminous IR galaxies ((U)LIRGs, LIR≫1011L☉).
We derive their atomic, molecular gas, and dense molecular gas masses
using newly available HI, CO, and HCN data from the literature, and SF
rates are determined both from total IR (8-1000um) and 1.4GHz radio
continuum (RC) luminosities. In order to derive the disk-averaged
surface densities of gas and SF rates, we have taken a novel approach
and used high-resolution RC observations to measure the radio sizes
for all 181 galaxies. In our sample, we find that the surface density
of dense molecular gas (as traced by HCN) has the tightest correlation
with that of SF rates (ΣSFR), and is linear in log-log space
(power-law slope of N=1.01±0.02) across the full galaxy sample. The
correlation between surface densities of molecular gas (ΣH2,
traced by CO) and ΣSFR is sensitive to the adopted value of
the CO-to-H2 conversion factor (αCO) used to infer molecular
gas masses from CO luminosities. For a fixed Galactic value of
αCO, a power law index of 1.14±0.02 is found. If instead we
adopt values for αCO of 4.6 and 0.8 for disk galaxies and
(U)LIRGs, respectively, we find the two galaxy populations separate
into two distinct ΣSFR versus ΣH2 relations. Finally,
applying a continuously varying αCO to our sample, we recover
a single ΣSFR-ΣH2 relation with slope of
1.60±0.03. The ΣSFR is a steeper function of total gas
Σgas (molecular gas with atomic gas) than that of molecular
gas ΣH2, and are tighter among low-luminosity galaxies. We
find no correlation between global surface densities of SFRs and
atomic gas (HI).
Description:
HI maps or sizes for 95 of the 115 normal star-forming galaxies in our
sample were obtained from HI imaging surveys carried out with the
(J)VLA and the Westerbork Synthesis Radio Telescope (see section 2.2.1
for the detailed surveys used).
Velocity-integrated CO fluxes were gathered from the literature and,
when available, preference was given to CO fluxes derived directly
from galaxy-integrated imaging measurements (see section 2.2.2).
In order to obtain the largest possible HCN (1-0) sample, we collected
all robust measurements available in the literature (see section
2.2.3).
Total-IR 8-1000um luminosities were calculated using 12, 25, 60, 100um
photometry from the Infrared Astronomical Satellite (IRAS) and the
formulas presented in Table 1 of Sanders & Mirabel (1996ARA&A..34..749S 1996ARA&A..34..749S).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 74 181 Luminosities
table2.dat 101 181 Surface density
refs.dat 102 92 References
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See also:
VIII/81 : Sydney University Molonglo Sky Survey (SUMSS V2.1) (Mauch+ 2008)
VIII/71 : The FIRST Survey Catalog, Version 03Apr11 (Becker+ 2003)
VIII/65 : 1.4GHz NRAO VLA Sky Survey (NVSS) (Condon+ 1998)
II/156 : IRAS Faint Source Catalog, |b| > 10, Version 2.0 (Moshir+ 1989)
II/125 : IRAS catalogue of Point Sources, Version 2.0 (IPAC 1986)
J/AJ/144/134 : LITTLE THINGS survey of nearby dwarf galaxies (Hunter+, 2012)
J/ApJ/723/993 : Spatial extent of (U)LIRGs in the MIR. I. (Diaz-Santos+, 2010)
J/A+A/522/A3 : M33 CO(2-1) and HI integrated intensity maps (Gratier+, 2010)
J/ApJ/704/842 : VIRUS-P spectroscopy of NGC 5194 (Blanc+, 2009)
J/AJ/136/2782 : Star formation efficiency in nearby galaxies (Leroy+, 2008)
J/AJ/136/2563 : HI Nearby Galaxy Survey, THINGS (Walter+, 2008)
J/ApJ/671/333 : Aperture photometry in NGC 5194 (Kennicutt+, 2007)
J/A+A/462/507 : AMIGA III. IRAS data (Lisenfeld+, 2007)
J/A+A/462/81 : LIR-Tdust relation in galaxies (Chanial+, 2007)
J/A+A/442/137 : HI observations of WHISP disk galaxies (Noordermeer+, 2005)
J/AJ/126/1607 : IRAS Revised Bright Galaxy Sample (Sanders+, 2003)
J/A+A/390/863 : CCD R Photometry of WHISP Dwarf Galaxies (Swaters, 2002)
J/ApJ/554/803 : New VLA Sky Survey (NVSS) of IRAS 2 Jy Galaxies (Yun+ 2001)
J/A+AS/131/73 : Catalogue of HI maps of galaxies. I. (Martin 1998)
J/A+AS/115/439 : CO survey of galaxies (Elfhag+, 1996)
J/A+AS/115/407 : Short WSRT HI observations of spiral galaxies (Rhee+, 1996)
J/ApJS/73/359 : 1.49 GHz atlas of the IRAS bright galaxies (Condon+, 1990)
J/ApJS/65/485 : 1.49GHz Atlas of Spiral Galaxies (Condon, 1987)
http://archive.nrao.edu/ : NRAO archive home page
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 7 A7 --- Type Galaxy type: "Normal" Galaxies or
"(U)LIRG" = (ultra)luminous IR Galaxy
8- 15 A8 --- --- [Galaxies ]
17- 26 A10 --- Name Identifier
28- 33 F6.2 Mpc Dist [0.8/313.6] Distance
35- 40 F6.2 10+8K.km/s LCO [0.01/226.5] The CO line luminosity
42- 46 F5.2 10+8K.km/s LHCN [0.02/50.6]? The HCN line luminosity
48- 52 F5.2 Lsun LIR [7.8/12.5] Total 8-1000 micron luminosity
54- 59 F6.2 ZW/Hz LRC [-6.4/864] The 1.4GHz radio continuum luminosity
(in 10+21W.Hz-1)
61- 74 A14 --- Ref Luminosity references (see refs.dat file)
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 7 A7 --- Type Galaxy type: "Normal" Galaxies or
"(U)LIRG" = (ultra)luminous IR Galaxy
8- 15 A8 --- --- [Galaxies ]
17- 26 A10 --- Name Galaxy identifier
28- 34 F7.2 arcsec Diam1 Diameter (deconvolved major axes)
36- 39 F4.2 arcsec Diam2 ? Second diameter for interacting
galaxies (1)
41- 45 F5.2 [Msun/pc2] logSHI [-0.6/1.3]? Log HI atomic surface density
47- 51 F5.2 [Msun/pc2] logSH2a [-0.4/6.1] Log molecular H2 gas mass
surface density (2)
53- 57 F5.2 [Msun/pc2] logSH2b [-0.2/4.9] Log molecular H2 gas mass
surface density (3)
59- 63 F5.2 [Msun/pc2] logSgas [-0.2/6.1] Log total gas surface density
65- 69 F5.2 [Msun/pc2] logSden [-0.5/5.5]? Log dense molecular gas
surface density
71- 75 F5.2 [Msun/yr/kpc2] logSIR [-2.8/3.9] Star formation rate from
8-1000µm
77- 81 F5.2 [Msun/yr/kpc2] logSRC [-3.2/3.6] Star formation rate from
1.4GHz radio continuum
83- 89 A7 --- Ref2 References (see refs.dat file)
91-101 A11 --- NRAO Project code(s) in NRAO archive (4)
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Note (1): For interacting galaxies which clearly show two independent
components, such as Arp 055 and Arp 220, we gave the radio sizes
for both components.
Note (2): Calculated using a fixed CO-to-H2 conversion factor value of
4.6 solar masses (K.km/s.pc2)-1.
Note (3): Calculated using continuously-varying αCO.
Note (4): See NRAO archive (http://archive.nrao.edu/).
The (J)VLA observation project codes were given for the radio images
reduced in this work. Two project codes were given in the cases that
the data sets from two different (J)VLA configurations were combined.
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Byte-by-byte Description of file: refs.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 I3 --- Ref [1/140] Reference code (1)
5- 23 A19 --- BibCode Bibcode
25- 47 A23 --- Auth First author's name(s)
49-102 A54 --- Comm Comment
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Note (1): Reference number 1-19 are for CO data, 20-35 are for HCN data,
36-41 for IR data and 42-52 for 1.4GHz radio continuum data;
101-112 are references for the Radio map and
113-140 for the HI atomic surface density.
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 03-Sep-2015