NASA/IPAC EXTRAGALACTIC DATABASE
Date and Time of the Query: 2019-06-24 T02:34:03 PDT
Help | Comment | NED Home

For refcode 2011AJ....142...37S:
Retrieve 33 NED objects in this reference.
Please click here for ADS abstract

NED Abstract

Copyright by American Astronomical Society. Reproduced by permission
2011AJ....142...37S A Molecular Star Formation Law in the Atomic-gas-dominated Regime in Nearby Galaxies Schruba, Andreas; Leroy, Adam K.; Walter, Fabian; Bigiel, Frank; Brinks, Elias; de Blok, W. J. G.; Dumas, Gaelle; Kramer, Carsten; Rosolowsky, Erik; Sandstrom, Karin; Schuster, Karl; Usero, Antonio; Weiss, Axel; Wiesemeyer, Helmut Abstract. We use the IRAM HERACLES survey to study CO emission from 33 nearby spiral galaxies down to very low intensities. Using 21 cm line atomic hydrogen (H I) data, mostly from THINGS, we predict the local mean CO velocity based on the mean H I velocity. By re-normalizing the CO velocity axis so that zero corresponds to the local mean H I velocity we are able to stack spectra coherently over large regions. This enables us to measure CO intensities with high significance as low as I_CO_ ~ 0.3 K km s^--1^ ({SIGMA}_H__2_ ~ 1 M {sun} pc^--2^), an improvement of about one order of magnitude over previous studies. We detect CO out to galactocentric radii r_gal_ ~ r_25_ and find the CO radial profile to follow a remarkably uniform exponential decline with a scale length of ~0.2 r_25_. Here we focus on stacking as a function of radius, comparing our sensitive CO profiles to matched profiles of H I, H{alpha}, far-UV (FUV), and Infrared (IR) emission at 24 micron and 70 micron. We observe a tight, roughly linear relationship between CO and IR intensity that does not show any notable break between regions that are dominated by molecular gas ({SIGMA}_H__2_ > {SIGMA}_HI_) and those dominated by atomic gas ({SIGMA}_H__2_ < {SIGMA}_HI_). We use combinations of FUV+24 micron and H{alpha}+24 micron to estimate the recent star formation rate (SFR) surface density, {SIGMA}_SFR_, and find approximately linear relations between {SIGMA}_SFR_ and {SIGMA}_H__2_. We interpret this as evidence of stars forming in molecular gas with little dependence on the local total gas surface density. While galaxies display small internal variations in the SFR-to-H_2_ ratio, we do observe systematic galaxy-to-galaxy variations. These galaxy-to-galaxy variations dominate the scatter in relationships between CO and SFR tracers measured at large scales. The variations have the sense that less massive galaxies exhibit larger ratios of SFR-to-CO than massive galaxies. Unlike the SFR-to-CO ratio, the balance between atomic and molecular gas depends strongly on the total gas surface density and galactocentric radius. It must also depend on additional parameters. Our results reinforce and extend to lower surface densities, a picture in which star formation in galaxies can be separated into two processes: the assembly of star-forming molecular clouds and the formation of stars from H_2_. The interplay between these processes yields a total gas-SFR relation with a changing slope, which has previously been observed and identified as a star formation threshold. Key words: galaxies: evolution, galaxies: ISM, radio lines: galaxies, stars: formation
Retrieve 33 NED objects in this reference.
Please click here for ADS abstract

Back to NED Home