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|Title:||ALMA reveals starburst-like interstellar medium conditions in a compact star-forming galaxy at z 2 using [CI] and CO||Authors:||Popping, G.
de Breuck, C.
van Dokkum, P.G.
van Kampen, E.
|Issue Date:||2017||Journal:||ASTRONOMY & ASTROPHYSICS||Abstract:||We present ALMA detections of the [CI] 1-0, CO J = 3-2, and CO J = 4-3 emission lines, as well as the ALMA band 4 continuum for a compact star-forming galaxy (cSFG) at z = 2.225, 3D-HST GS30274. As is typical for cSFGs, this galaxy has a stellar mass of 1.89 ± 0.47 × 1011M☉, with a star formation rate (SFR) of 214 ± 44 M☉ yr-1 putting it on the star-forming "main-sequence", but with an H-band effective radius of 2.5 kpc, making it much smaller than the bulk of "main-sequence" star-forming galaxies. The intensity ratio of the line detections yield an ISM density ( 6 × 104 cm-3) and a UV-radiation field ( 2 × 104G0), similar to the values in local starburst and ultra-luminous infrared galaxy environments. A starburst phase is consistent with the short depletion times (tH2,dep ≤ 140 Myr) we find in 3D-HST GS30274 using three different proxies for the H2 mass ([CI], CO, dust mass). This depletion time is significantly shorter than in more extended SFGs with similar stellar masses and SFRs. Moreover, the gas fraction of 3D-HST GS30274 is smaller than typically found in extended galaxies. We measure the CO and [CI] kinematics and find a FWHM line width of 750 ± 41 km s-1. The CO and [CI] FWHM are consistent with a previously measured Hα FWHM for this source. The line widths are consistent with gravitational motions, suggesting we are seeing a compact molecular gas reservoir. A previous merger event, as suggested by the asymmetric light profile, may be responsible for the compact distribution of gas and has triggered a central starburst event. This event gives rise to the starburst-like ISM properties and short depletion times in 3D-HST GS30274. The centrally located and efficient star formation is quickly building up a dense core of stars, responsible for the compact distribution of stellar light in 3D-HST GS30274.||URI:||http://hdl.handle.net/20.500.12386/30227||URL:||https://www.aanda.org/articles/aa/full_html/2017/06/aa30391-17/aa30391-17.html||ISSN:||0004-6361||DOI:||10.1051/0004-6361/201730391||Bibcode ADS:||2017A&A...602A..11P||Fulltext:||open|
|Appears in Collections:||1.01 Articoli in rivista|
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checked on Jun 15, 2021
checked on Jun 15, 2021
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