COLD DUST BUT WARM GAS IN THE UNUSUAL ELLIPTICAL GALAXY NGC 4125
- Department of Physics and Astronomy, McMaster University, Hamilton, ON L8S 4M1 (Canada)
- Institut d'Astrophysique de Paris, Université Pierre et Marie Curie, CNRS UMR 7095, F-75014 Paris (France)
- Laboratoire AIM, CEA/DSM-CNRS-Université Paris Diderot DAPNIA/Service d'Astrophysique, Bât. 709, CEA-Saclay, F-91191 Gif-sur-Yvette Cedex (France)
- School of Physics and Astronomy, Cardiff University, The Parade, Cardiff CF24 3AA (United Kingdom)
- Sterrenkundig Observatorium, Universiteit Gent, Krijgslaan 281 S9, B-9000 Gent (Belgium)
- UK ALMA Regional Centre Node, Jodrell Bank Center for Astrophysics, School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL (United Kingdom)
- Aix-Marseille Université, CNRS, LAM (Laboratoire d'Astrophysique de Marseille) UMR 7326, F-13388 Marseille (France)
- Astrophysics Group, Imperial College London, Blackett Laboratory, Prince Consort Road, London SW7 2AZ (United Kingdom)
- Department of Physics and Astronomy, University of California, Irvine, CA 92697 (United States)
- Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA (United Kingdom)
Data from the Herschel Space Observatory have revealed an unusual elliptical galaxy, NGC 4125, which has strong and extended submillimeter emission from cold dust but only very strict upper limits to its CO and H I emission. Depending on the dust emissivity, the total dust mass is 2-5 × 10{sup 6} M {sub ☉}. While the neutral gas-to-dust mass ratio is extremely low (<12-30), including the ionized gas traced by [C II] emission raises this limit to <39-100. The dust emission follows a similar r {sup 1/4} profile to the stellar light and the dust to stellar mass ratio is toward the high end of what is found in nearby elliptical galaxies. We suggest that NGC 4125 is currently in an unusual phase where evolved stars produced in a merger-triggered burst of star formation are pumping large amounts of gas and dust into the interstellar medium. In this scenario, the low neutral gas-to-dust mass ratio is explained by the gas being heated to temperatures ≥10{sup 4} K faster than the dust is evaporated. If galaxies like NGC 4125, where the far-infrared emission does not trace neutral gas in the usual manner, are common at higher redshift, this could have significant implications for our understanding of high redshift galaxies and galaxy evolution.
- OSTI ID:
- 22215424
- Journal Information:
- Astrophysical Journal Letters, Vol. 776, Issue 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 2041-8205
- Country of Publication:
- United States
- Language:
- English
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