Widespread HCO emission in the M82's nuclear starburst

Abstract

We present a high-resolution (~ 5'') image of the nucleus of M82 showing the presence of widespread emission of the formyl radical (HCO). The HCO map, the first obtained in an external galaxy, reveals the existence of a structured disk of ~ 650 pc full diameter. The HCO distribution in the plane mimics the ring morphology displayed by other molecular/ionized gas tracers in M82. More precisely, rings traced by HCO, CO and HII regions are nested, with the HCO ring lying in the outer edge of the molecular torus. Observations of HCO in galactic clouds indicate that the abundance of HCO is strongly enhanced in the interfaces between the ionized and molecular gas. The surprisingly high overall abundance of HCO measured in M82 (X(HCO) ~ 4x10^{-10}) indicates that its nuclear disk can be viewed as a giant Photon Dominated Region (PDR) of ~ 650 pc size. The existence of various nested gas rings, with the highest HCO abundance occurring at the outer ring (X(HCO) ~ 0.8x10^{-9}), suggests that PDR chemistry is propagating in the disk. We discuss the inferred large abundances of HCO in M82 in the context of a starburst evolutionary scenario, picturing the M82 nucleus as an evolved starburst.

arXiv comment13 pages, 3 figures, to appear in ApJ Letters; corrected list of authors

References in corpus (5)

• The Asymmetric Wind in M82
• The effect of violent star formation on the state of the molecular gas in M82
• Detection of the Red Giant Branch Stars in M82 Using the Hubble Space Telescope
• Atomic Carbon in M82: Physical conditions derived from simultaneous observations of the [CI] fine structure submillimeter wave transitions
• SiO chimneys and supershells in M82

Cited by in corpus (51)

• 2021 Census of Interstellar, Circumstellar, Extragalactic, Protoplanetary Disk, and Exoplanetary Molecules
• 2018 Census of Interstellar, Circumstellar, Extragalactic, Protoplanetary Disk, and Exoplanetary Molecules
• A multi-transition HCN and HCO+ study of 12 nearby active galaxies: AGN versus SB environments
• A 2 mm spectral line survey of the starburst galaxy NGC 253
• Spatially Resolved Chemistry in Nearby Galaxies I. The Center of IC 342
• Molecular Gas Chemistry in AGN I. The IRAM Survey of NGC1068
• Photodissociation and X-Ray Dominated Regions
• Molecules at z=0.89: A 4-mm-rest-frame absorption line survey toward PKS 1830-211
• Molecular line emission in NGC1068 imaged with ALMA: II. The chemistry of the dense molecular gas
• Dense gas in luminous infrared galaxies
• Tracing shocks and photodissociation in the Galactic center region
• Dense gas in nearby galaxies XVI. The nuclear starburst environment in NGC4945
• Lambda = 3 mm line survey of nearby active galaxies
• Photon-Dominated Chemistry in the Nucleus of M82: Widespread HOC+ emission in the inner 650 pc disk
• Molecules in galaxies
• A lambda = 1.3 mm and 2 mm molecular line survey towards M82
• HNCO abundances in galaxies: Tracing the evolutionary state of starbursts
• HCO mapping of the Horsehead : Tracing the illuminated dense molecular cloud surfaces
• Dense gas in nearby galaxies: XV. Hot ammonia in NGC253, Maffei2 and IC342
• CS, HC3N and CH3CCH multi-line analyses towards starburst galaxies. The evolution of cloud structures in the central regions of galaxies
• Extragalactic CS survey
• Photodissociation chemistry footprints in the Starburst galaxy NGC 253
• Spectral line survey of the ultracompact HII region Mon R2
• On the chemistry and distribution of HOC+ in M82: More evidence for extensive PDRs
• HIFI spectroscopy of low-level water transitions in M82
• Large-scale molecular shocks in galaxies: the SiO interferometer map of IC342
• Formaldehyde as a Tracer of Extragalactic Molecular Gas I. Para-H_2CO Emission From M 82
• Detection of extragalactic H3O+
• Molecular shock tracers in NGC 1068: SiO and HNCO
• Detection of CO+ in the nucleus of M82
• 3 mm spectral line survey of two lines of sight toward two typical cloud complexes in the Galactic Center
• Molecular line emission in NGC 4945, imaged with ALMA
• Detections of C2H, cyclic-C3H2, and H13CN in NGC 1068
• Methanol detection in M82
• The interstellar medium of the Antennae Galaxies
• The JCMT Spectral Legacy Survey
• Tracing high density gas in M 82 and NGC 4038
• Cyanoacetylene in IC 342: An Evolving Dense Gas Component with Starburst Age
• Insights into the Carbon chemistry of Mon R2
• The chemical footprint of AGN feedback in the outflowing circumnuclear disk of NGC 1068
• Reconstructing the shock history in the CMZ of NGC 253 with ALCHEMI
• SMA High Angular Resolution Imaging of the Lensed Quasar APM08279+5255
• The chemical footprint of the star formation feedback in M 82 on scales of 100 pc
• New Detections of Galactic Molecular Absorption Systems toward ALMA Calibrator Sources
• High-resolution molecular line observations of active galaxies
• ATLASGAL-selected massive clumps in the inner Galaxy: VIII. Chemistry of photodissociation regions
• Properties of dense molecular gas along the major axis of M 82
• Extragalactic chemistry of molecular gas: lessons from the local universe
• Chemical Complexity in Galaxies
• The MALATANG survey: Dense gas distribution on sub-kiloparsec scales across the disk of M82
• Molecular line probes of activity in galaxies