TY - JOUR
T1 - The implications of the surprising existence of a large, massive CO disk in a distant protocluster
AU - Dannerbauer, H.
AU - Lehnert, M. D.
AU - Emonts, B.
AU - Ziegler, B.
AU - Altieri, B.
AU - De Breuck, C.
AU - Hatch, N.
AU - Kodama, T.
AU - Koyama, Y.
AU - Kurk, J. D.
AU - Matiz, T.
AU - Miley, G.
AU - Narayanan, D.
AU - Norris, R. P.
AU - Overzier, R.
AU - Röttgering, H. J.A.
AU - Sargent, M.
AU - Seymour, N.
AU - Tanaka, M.
AU - Valtchanov, I.
AU - Wylezalek, D.
N1 - Funding Information:
Acknowledgements. The Australia Telescope Compact Array is funded by the Commonwealth of Australia for operation as a National Facility managed by CSIRO. The authors wish to express their sincerest thanks to the staff of the CSIRO for their assistance in conducting these observations and to the program committee for their generous allocation of time and continuing support for our research. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. We thank the anonymous referee for her or his comments that helped us to improve our arguments and presentation in this
Publisher Copyright:
© ESO, 2017.
PY - 2017/12/1
Y1 - 2017/12/1
N2 - It is not yet known if the properties of molecular gas in distant protocluster galaxies are significantly affected by their environment as galaxies are in local clusters. Through a deep, 64 h of effective on-source integration with the Australian Telescope Compact Array (ATCA), we discovered a massive, Mmol = 2.0 ± 0.2× 1011 M⊙, extended, ∼40 kpc, CO(1-0)-emitting disk in the protocluster surrounding the radio galaxy, MRC 1138-262. The galaxy, at zCO = 2.1478, is a clumpy, massive disk galaxy, M∗ ∼ 5 × 1011 M⊙, which lies 250 kpc in projection from MRC 1138-262 and is a known Hα emitter, named HAE229. This source has a molecular gas fraction of ∼30%. The CO emission has a kinematic gradient along its major axis, centered on the highest surface brightness rest-frame optical emission, consistent with HAE229 being a rotating disk. Surprisingly, a significant fraction of the CO emission lies outside of the UV/optical emission. In spite of this, HAE229 follows the same relation between star-formation rate and molecular gas mass as normal field galaxies. HAE229 is the first CO(1-0) detection of an ordinary, star-forming galaxy in a protocluster. We compare a sample of cluster members at z > 0.4 thatare detected in low-order CO transitions, with a similar sample of sources drawn from the field. We confirm findings that the CO-luminosity and full-width at half maximum are correlated in starbursts and show that this relation is valid for normal high-z galaxies as well as for those in overdensities. We do not find a clear dichotomy in the integrated Schmidt-Kennicutt relation for protocluster and field galaxies. Our results suggest that environment does not have an impact on the "star-formation efficiency" or the molecular gas content of high-redshift galaxies. Not finding any environmental dependence in these characteristics, especially for such an extended CO disk, suggests that environmentally-specific processes such as ram pressure stripping do not operate efficiently in (proto)clusters.
AB - It is not yet known if the properties of molecular gas in distant protocluster galaxies are significantly affected by their environment as galaxies are in local clusters. Through a deep, 64 h of effective on-source integration with the Australian Telescope Compact Array (ATCA), we discovered a massive, Mmol = 2.0 ± 0.2× 1011 M⊙, extended, ∼40 kpc, CO(1-0)-emitting disk in the protocluster surrounding the radio galaxy, MRC 1138-262. The galaxy, at zCO = 2.1478, is a clumpy, massive disk galaxy, M∗ ∼ 5 × 1011 M⊙, which lies 250 kpc in projection from MRC 1138-262 and is a known Hα emitter, named HAE229. This source has a molecular gas fraction of ∼30%. The CO emission has a kinematic gradient along its major axis, centered on the highest surface brightness rest-frame optical emission, consistent with HAE229 being a rotating disk. Surprisingly, a significant fraction of the CO emission lies outside of the UV/optical emission. In spite of this, HAE229 follows the same relation between star-formation rate and molecular gas mass as normal field galaxies. HAE229 is the first CO(1-0) detection of an ordinary, star-forming galaxy in a protocluster. We compare a sample of cluster members at z > 0.4 thatare detected in low-order CO transitions, with a similar sample of sources drawn from the field. We confirm findings that the CO-luminosity and full-width at half maximum are correlated in starbursts and show that this relation is valid for normal high-z galaxies as well as for those in overdensities. We do not find a clear dichotomy in the integrated Schmidt-Kennicutt relation for protocluster and field galaxies. Our results suggest that environment does not have an impact on the "star-formation efficiency" or the molecular gas content of high-redshift galaxies. Not finding any environmental dependence in these characteristics, especially for such an extended CO disk, suggests that environmentally-specific processes such as ram pressure stripping do not operate efficiently in (proto)clusters.
KW - Galaxies: ISM
KW - Galaxies: clusters: individual: MRC 1138, 262
KW - Galaxies: evolution
KW - Galaxies: high-redshift
KW - Galaxies: individual: HAE229
KW - Submillimeter: galaxies
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U2 - 10.1051/0004-6361/201730449
DO - 10.1051/0004-6361/201730449
M3 - Article
AN - SCOPUS:85037738186
SN - 0004-6361
VL - 608
JO - Astronomy and Astrophysics
JF - Astronomy and Astrophysics
M1 - A48
ER -