Carma survey toward infrared-bright nearby galaxies (STING): Molecular gas star formation law in NGC 4254

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This study explores the effects of different assumptions and systematics on the determination of the local, spatially resolved star formation law. Using four star formation rate (SFR) tracers (Hα with azimuthally averaged extinction correction, mid-infrared 24 μm, combined Hα and mid-infrared 24 μm, and combined far-ultraviolet and mid-infrared 24 μm), several fitting procedures, and different sampling strategies, we probe the relation between SFR and molecular gas at various spatial...[Show more]

dc.contributor.author Rahman, N. Bolatto, Alberto Wong, T Leroy, Adam K. Walter, Fabian Rosolowsky, Erik West, Andrew A. Bigiel, Frank Ott, Juergen Xue, Rui Jameson, Katherine 2018-11-29T22:52:40Z 2018-11-29T22:52:40Z 0004-637X http://hdl.handle.net/1885/152241 This study explores the effects of different assumptions and systematics on the determination of the local, spatially resolved star formation law. Using four star formation rate (SFR) tracers (Hα with azimuthally averaged extinction correction, mid-infrared 24 μm, combined Hα and mid-infrared 24 μm, and combined far-ultraviolet and mid-infrared 24 μm), several fitting procedures, and different sampling strategies, we probe the relation between SFR and molecular gas at various spatial resolutions (500 pc and larger) and surface densities ($\hbox{$\Sigma _{{\rm H}_2}$}\approx 10\hbox{--}245$ M ☉ pc–2) within the central ~6.5 kpc in the disk of NGC 4254. We explore the effect of diffuse emission using an unsharp masking technique with varying kernel size. The fraction of diffuse emission, f DE, thus determined is a strong inverse function of the size of the filtering kernel. We find that in the high surface brightness regions of NGC 4254 the form of the molecular gas star formation law is robustly determined and approximately linear (~0.8-1.1) and independent of the assumed fraction of diffuse emission and the SFR tracer employed. When the low surface brightness regions are included, the slope of the star formation law depends primarily on the assumed fraction of diffuse emission. In such a case, results range from linear when the fraction of diffuse emission in the SFR tracer is f DE lesssim 30% (or when diffuse emission is removed in both the star formation and the molecular gas tracer) to super-linear (~1.4) when f DE gsim 50%. We find that the tightness of the correlation between gas and star formation varies with the choice of star formation tracer. The 24 μm SFR tracer by itself shows the tightest correlation with the molecular gas surface density, whereas the Hα corrected for extinction using an azimuthally averaged correction shows the highest dispersion. We find that for R < 0.5R 25 the local star formation efficiency is constant and similar to that observed in other large spirals, with a molecular gas depletion time τdep ~ 2 Gyr. application/pdf IOP Publishing The Astrophysical Journal Carma survey toward infrared-bright nearby galaxies (STING): Molecular gas star formation law in NGC 4254 Journal article Imported from ARIES 730 2011 020199 - Astronomical and Space Sciences not elsewhere classified u4351680xPUB114 Published Version Rahman, N., University of Maryland Bolatto, Alberto, University of Maryland Wong, T, University of Illinois Leroy, Adam K., National Radio Astronomy Observatory Walter, Fabian, Max Planck Institute for Astronomy Rosolowsky, Erik, University of British Columbia West, Andrew A., Boston University Bigiel, Frank, University of California Ott, Juergen, National Radio Astronomy Observatory Xue, Rui, University of Illinois Jameson, Katherine, College of Science, ANU 2 10.1088/0004-637X/730/2/72 2018-11-29T07:47:36Z 2-s2.0-79953689951 000288441900012 Open Access ANU Research Publications