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

Date

2011

Authors

Rahman, N.
Bolatto, Alberto
Wong, T
Leroy, Adam K.
Walter, Fabian
Rosolowsky, Erik
West, Andrew A.
Bigiel, Frank
Ott, Juergen
Xue, Rui

Journal Title

Journal ISSN

Volume Title

Publisher

IOP Publishing

Abstract

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.

Description

Keywords

Citation

Source

The Astrophysical Journal

Type

Journal article

Book Title

Entity type

Access Statement

Open Access

License Rights

Restricted until

Back to topicon-arrow-up-solid
 
APRU
IARU
 
edX
Group of Eight Member

Acknowledgement of Country

The Australian National University acknowledges, celebrates and pays our respects to the Ngunnawal and Ngambri people of the Canberra region and to all First Nations Australians on whose traditional lands we meet and work, and whose cultures are among the oldest continuing cultures in human history.


Contact ANUCopyrightDisclaimerPrivacyFreedom of Information

+61 2 6125 5111 The Australian National University, Canberra

TEQSA Provider ID: PRV12002 (Australian University) CRICOS Provider Code: 00120C ABN: 52 234 063 906