K. V. Croxall

The CO-to-H2 Conversion Factor and Dust-to-gas Ratio on Kiloparsec Scales in Nearby Galaxies

We present ~kiloparsec spatial resolution maps of the CO-to-H_2 conversion factor (α_(CO)) and dust-to-gas ratio (DGR) in 26 nearby, star-forming galaxies. We have simultaneously solved for α_(CO) and the DGR by assuming that the DGR is approximately constant on kiloparsec scales. With this assumption, we can combine maps of dust mass surface density, CO-integrated intensity, and H I column density to solve for both αCO and the DGR with no assumptions about their value or dependence on metallicity or other parameters. Such a study has just become possible with the availability of high-resolution far-IR maps from the Herschel key program KINGFISH, ^(12)CO J = (2-1) maps from the IRAM 30 m large program HERACLES, and H I 21 cm line maps from THINGS. We use a fixed ratio between the (2-1) and (1-0) lines to present our α_(CO) results on the more typically used ^(12)CO J = (1-0) scale and show using literature measurements that variations in the line ratio do not affect our results. In total, we derive 782 individual solutions for α_(CO) and the DGR. On average, α_(CO) = 3.1 M_☉ pc^(–2) (K km s^(–1))^(–1) for our sample with a standard deviation of 0.3 dex. Within galaxies, we observe a generally flat profile of α_(CO) as a function of galactocentric radius. However, most galaxies exhibit a lower α_(CO) value in the central kiloparsec—a factor of ~2 below the galaxy mean, on average. In some cases, the central α_(CO) value can be factors of 5-10 below the standard Milky Way (MW) value of α_(CO,MW) = 4.4 M_☉ pc^(–2) (K km s^(–1))^(–1). While for α_(CO) we find only weak correlations with metallicity, the DGR is well-correlated with metallicity, with an approximately linear slope. Finally, we present several recommendations for choosing an appropriate α_(CO) for studies of nearby galaxies.

KINGFISH—Key Insights on Nearby Galaxies: A Far-Infrared Survey with Herschel: Survey Description and Image Atlas

The KINGFISH project (Key Insights on Nearby Galaxies: a Far-Infrared Survey with Herschel) is an imaging and spectroscopic survey of 61 nearby (d < 30 Mpc) galaxies, chosen to cover a wide range of galaxy properties and local interstellar medium (ISM) environments found in the nearby universe. Its broad goals are to characterize the ISM of present-day galaxies, the heating and cooling of their gaseous and dust components, and to better understand the physical processes linking star formation and the ISM. KINGFISH is a direct descendant of the Spitzer Infrared Nearby Galaxies Survey (SINGS), which produced complete Spitzer imaging and spectroscopic mapping and a comprehensive set of multiwavelength ancillary observations for the sample. The Herschel imaging consists of complete maps for the galaxies at 70, 100, 160, 250, 350, and 500 μm. The spectral line imaging of the principal atomic ISM cooling lines ([O I] 63 μm, [O III] 88 μm, [N II] 122,205 μm, and [C II] 158 μm) covers the subregions in the centers and disks that already have been mapped in the mid-infrared with Spitzer. The KINGFISH and SINGS multiwavelength data sets combined provide panchromatic mapping of the galaxies sufficient to resolve individual star-forming regions, and tracing the important heating and cooling channels of the ISM, across a wide range of local extragalactic ISM environments. This article summarizes the scientific strategy for KINGFISH, the properties of the galaxy sample, the observing strategy, and data processing and products. It also presents a combined Spitzer and Herschel image atlas for the KINGFISH galaxies, covering the wavelength range 3.6–500 μm. All imaging and spectroscopy data products will be released to the Herschel user-generated product archives.

[C II] 158 μm EMISSION AS A STAR FORMATION TRACER

The [CII] 157.74

Calibration of the total infrared luminosity of nearby galaxies from Spitzer and Herschel bands

\mu

THE TYPECASTING OF ACTIVE GALACTIC NUCLEI: Mrk 590 NO LONGER FITS THE ROLE

m transition is the dominant coolant of the neutral interstellar gas, and has great potential as a star formation rate (SFR) tracer. Using the Herschel KINGFISH sample of 46 nearby galaxies, we investigate the relation of [CII] surface brightness and luminosity with SFR. We conclude that [CII] can be used for measurements of SFR on both global and kiloparsec scales in normal star-forming galaxies in the absence of strong active galactic nuclei (AGN). The uncertainty of the

Mapping Dust through Emission and Absorption in Nearby Galaxies

\Sigma_{\rm [CII]}-\Sigma_{\rm SFR}

DUST CONTINUUM EMISSION AS A TRACER OF GAS MASS IN GALAXIES

calibration is

Herschel-SPIRE Fourier transform spectroscopy of the nearby spiral galaxy IC 342

\pm

Towards universal hybrid star formation rate estimators

0.21 dex. The main source of scatter in the correlation is associated with regions that exhibit warm IR colors, and we provide an adjustment based on IR color that reduces the scatter. We show that the color-adjusted

Shock Excited Molecules in NGC 1266: ULIRG Conditions at the Center of a Bulge-dominated Galaxy

\Sigma_{\rm[CII]}-\Sigma_{\rm SFR}