HERSCHEL EXPLOITATION OF LOCAL GALAXY ANDROMEDA (HELGA). III. THE STAR FORMATION LAW IN M31

Journal Article · Mon May 20 00:00:00 EDT 2013 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/769/1/55· OSTI ID:22126635

Ford, George P.; Gear, Walter K.; Smith, Matthew W. L.; Eales, Steve A.; Gomez, Haley L.; Kirk, Jason ^[1]; Baes, Maarten; De Looze, Ilse; Fritz, Jacopo; Gentile, Gianfranco; Gordon, Karl D.; Verstappen, Joris ^[2]; Bendo, George J. ^[3]; Boquien, Mederic; Boselli, Alessandro ^[4]; Cooray, Asantha R. ^[5]; Lebouteiller, Vianney ^[6]; O'Halloran, Brian ^[7]; Spinoglio, Luigi ^[8]; Wilson, Christine D. ^[9]

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1. School of Physics and Astronomy, Cardiff University, Queens Buildings, The Parade, Cardiff CF24 3AA (United Kingdom)
2. Sterrenkundig Observatorium, Universiteit Gent, Krijgslaan 281, B-9000 Gent (Belgium)
3. Jodrell Bank Centre for Astrophysics, University of Manchester, Alan Turing Building, Manchester M13 9PL (United Kingdom)
4. Aix Marseille Universite, CNRS, LAM (Laboratoire d'Astrophysique de Marseille) UMR 7326, F-13388 Marseille (France)
5. Department of Physics and Astronomy, University of California, Irvine, 4129 Frederick Reines Hall, Irvine, CA 92697-4575 (United States)
6. Service d'Astrophysique, l'Orme des Merisiers, CEA, Saclay, F-91191 Gif-sur-Yvette (France)
7. Astrophysics Group, Blackett Laboratory, Imperial College London, Prince Consort Road, London SW7 2AZ (United Kingdom)
8. INAF, Istituto di Fisica dello Spazio Interplanetario, Via Fosso del Cavaliere 100, Tor Vergata, I-00133 Roma (Italy)
9. Department of Physics and Astronomy, ABB-241, McMaster University, 1280 Main Street West, Hamilton, ON L8S 4M1 (Canada)

We present a detailed study of how the star formation rate (SFR) relates to the interstellar medium (ISM) of M31 at {approx}140 pc scales. The SFR is calculated using the far-ultraviolet and 24 {mu}m emission, corrected for the old stellar population in M31. We find a global value for the SFR of 0.25{sup +0.06}{sub -0.04} M{sub sun} yr{sup -1} and compare this with the SFR found using the total far-infrared luminosity. There is general agreement in regions where young stars dominate the dust heating. Atomic hydrogen (H I) and molecular gas (traced by carbon monoxide, CO) or the dust mass is used to trace the total gas in the ISM. We show that the global surface densities of SFR and gas mass place M31 among a set of low-SFR galaxies in the plot of Kennicutt. The relationship between SFR and gas surface density is tested in six radial annuli across M31, assuming a power law relationship with index, N. The star formation (SF) law using total gas traced by H I and CO gives a global index of N = 2.03 {+-} 0.04, with a significant variation with radius; the highest values are observed in the 10 kpc ring. We suggest that this slope is due to H I turning molecular at {Sigma}{sub Gas} {approx} 10 M{sub Sun} pc{sup -2}. When looking at H{sub 2} regions, we measure a higher mean SFR suggesting a better spatial correlation between H{sub 2} and SF. We find N {approx} 0.6 with consistent results throughout the disk-this is at the low end of values found in previous work and argues against a superlinear SF law on small scales.

• OSTI ID: 22126635
• Journal Information: Astrophysical Journal, Vol. 769, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
CARBON MONOXIDE
COMPARATIVE EVALUATIONS
CORRELATIONS
DENSITY
DUSTS
EMISSION
FAR ULTRAVIOLET RADIATION
LUMINOSITY
MASS
MILKY WAY
RESOURCE EXPLOITATION
RINGS
STARS
SURFACES