Gas and dust cooling along the major axis of M33 (HerM33es) -- Herschel/PACS [CII] and [OI] observations

Abstract

M33 is a gas rich spiral galaxy of the Local Group. We investigate the relationship between the two major gas cooling lines and the total infrared (TIR) dust continuum. We mapped the emission of gas and dust in M33 using the far-infrared lines of [CII] and [OI](63um) and the TIR. The line maps were observed with Herschel/PACS. These maps have 50pc resolution and form a ~370pc wide stripe along its major axis covering the sites of bright HII regions, but also more quiescent arm and inter-arm regions from the southern arm at 2kpc galacto-centric distance to the south out to 5.7kpc distance to the north. Full-galaxy maps of the continuum emission at 24um from Spitzer/MIPS, and at 70um, 100um, and 160um from PACS were combined to obtain a map of the TIR. TIR and [CII] intensities are correlated over more than two orders of magnitude. The range of TIR translates to a range of far ultraviolet (FUV) emission of G0,obs~2 to 200 in units of the average Galactic radiation field. The binned [CII]/TIR ratio drops with rising TIR, with large, but decreasing scatter. Fits of modified black bodies (MBBs) to the continuum emission were used to estimate dust mass surface densities and total gas column densities. A correction for possible foreground absorption by cold gas was applied to the [OI] data before comparing it with models of photon dominated regions (PDRs). Most of the ratios of [CII]/[OI] and ([CII]+[OI])/TIR are consistent with two model solutions. The median ratios are consistent with one solution at n~2x10^2 cm-3, G0~60, and and a second low-FUV solution at n~10^4 cm-3, G0~1.5. The bulk of the gas along the lines-of-sight is represented by a low-density, high-FUV phase with low beam filling factors ~1. A fraction of the gas may, however, be represented by the second solution.

Accepted for publication in Astronomy & Astrophysics

References in corpus (18)

• Infrared Emission from Interstellar Dust. IV. The Silicate-Graphite-PAH Model in the Post-Spitzer Era
• A Compendium of Far-Infrared Line and Continuum Emission for 227 Galaxies Observed by the Infrared Space Observatory
• The Herschel Dwarf Galaxy Survey: I. Properties of the low-metallicity ISM from PACS spectroscopy
• [CII] 158 $\mu$m Emission as a Star Formation Tracer
• The Herschel Comprehensive (U)LIRG Emission Survey (HerCULES): CO Ladders, fine structure lines, and neutral gas cooling
• Detection of the 205 um [NII] Line from the Carina Nebula
• A Herschel [CII] Galactic plane survey III: [CII] as a tracer of star formation
• Star formation in M33: multiwavelength signatures across the disk
• The Origins of [CII] Emission in Local Star-forming Galaxies
• The Spatially Resolved [CII] Cooling Line Deficit in Galaxies
• [CII] absorption and emission in the diffuse interstellar medium across the Galactic Plane
• Measuring star formation with resolved observations: the test case of M33
• Insights into gas heating and cooling in the disc of NGC 891 from Herschel far-infrared spectroscopy
• The Survey of Lines in M31 (SLIM): Investigating the Origins of [CII] Emission
• The molecular gas mass of M33
• The outflow of gas from the Centaurus A circumnuclear disk: atomic spectral line maps from Herschel-PACS and APEX
• The physical characteristics of the gas in the disk of Centaurus A using the Herschel Space Observatory
• The Survey of Lines in M31 (SLIM): The Drivers of the [CII]/TIR Variation

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