SERENDIPITOUS ALMA DETECTION OF A DISTANT CO-EMITTING X-RAY BRIGHT GALAXY
- Institute of Astronomy, The University of Tokyo, Mitaka, Tokyo 181-0015 (Japan)
- National Astronomical Observatory of Japan, Mitaka, Tokyo 181-8588 (Japan)
- Division of Physics and Astronomy, Kyoto University, Kitashirakawa-Oiwake-Cho, Sakyo, Kyoto 606-8502 (Japan)
- Department of Astronomy, University of Massachusetts, 710 North Pleasant Street, Amherst, MA 01003 (United States)
- Joint ALMA Observatory, Alonso de Cordova 3107, Vitacura, Santiago 763 0355 (Chile)
We report the detection of a distant star-forming galaxy, ALMA J010748.3–173028, which is identified by a 13σ emission line at 99.75 GHz (SΔv = 3.1 Jy km s{sup –1}), behind the nearby merging galaxies VV114 using the Atacama Large Millimeter/submillimeter Array (ALMA) Band 3. We also find an 880 μm counterpart with ALMA Band 7 (S {sub 880μm} = 11.2 mJy). A careful comparison of the intensities of the line and the continuum suggests that the line is a redshifted {sup 12}CO transition. A photometric redshift analysis using the infrared to radio data favors a CO redshift of z = 2.467, although z = 3.622 is acceptable. We also find a hard X-ray counterpart, suggesting the presence of a luminous (L {sub X} ∼ 10{sup 44} erg s{sup –1}) active galactic nucleus obscured by a large hydrogen column (N {sub H} ∼ 2 × 10{sup 23} cm{sup –2} if z = 2.47). A cosmological simulation shows that the chance detection rate of a CO-emitting galaxy at z > 1 with ≥1 Jy km s{sup –1} is ∼10{sup –3} per single ALMA field of view and 7.5 GHz bandwidth at 99.75 GHz. This demonstrates that ALMA has sufficient sensitivity to find an emission-line galaxy such as ALMA J010748.3–173028 even by chance, although the likelihood of stumbling across such a source is not high.
- OSTI ID:
- 22364008
- Journal Information:
- Astrophysical Journal Letters, Vol. 781, 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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