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ALMA reveals starburst-like interstellar medium conditions in a compact star-forming galaxy at z ~ 2 using [CI] and CO

Popping, Gergö; Decarli, Roberto; Man, Allison W.S.; Nelson, Erica J.; Béthermin, Matthieu; De Breuck, Carlos; Mainieri, Vincenzo; van Dokkum, Pieter G.; Gullberg, Bitten; van Kampen, Eelco; Spaans, Marco; Trager, Scott C.

ALMA reveals starburst-like interstellar medium conditions in a compact star-forming galaxy at z ~ 2 using [CI] and CO Thumbnail


Authors

Gergö Popping

Roberto Decarli

Allison W.S. Man

Erica J. Nelson

Matthieu Béthermin

Carlos De Breuck

Vincenzo Mainieri

Pieter G. van Dokkum

Bitten Gullberg

Eelco van Kampen

Marco Spaans

Scott C. Trager



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.

Citation

Popping, G., Decarli, R., Man, A. W., Nelson, E. J., Béthermin, M., De Breuck, C., …Trager, S. C. (2017). ALMA reveals starburst-like interstellar medium conditions in a compact star-forming galaxy at z ~ 2 using [CI] and CO. Astronomy & Astrophysics, 602, Article A11. https://doi.org/10.1051/0004-6361/201730391

Journal Article Type Article
Acceptance Date Mar 9, 2017
Online Publication Date May 24, 2017
Publication Date May 24, 2017
Deposit Date Jul 7, 2017
Publicly Available Date Mar 29, 2024
Journal Astronomy and astrophysics.
Print ISSN 0004-6361
Electronic ISSN 1432-0746
Publisher EDP Sciences
Peer Reviewed Peer Reviewed
Volume 602
Article Number A11
DOI https://doi.org/10.1051/0004-6361/201730391

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Copyright Statement
Reproduced with permission from Astronomy & Astrophysics, © ESO 2017





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