Ultraluminous star-forming galaxies and extremely luminous warm molecular hydrogen emission at z = 2.16 in the PKS1138-26 radio galaxy protocluster
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A deep Spitzer Infrared Spectrograph map of the PKS 1138–26 galaxy protocluster reveals ultraluminous polycyclic aromatic hydrocarbon (PAH) emission from obscured star formation in three protocluster galaxies, including Hα-emitter (HAE) 229, HAE 131, and the central Spiderweb Galaxy. Star formation rates of ~500-1100 M ☉ yr–1 are estimated from the 7.7 μm PAH feature. At such prodigious formation rates, the galaxy stellar masses will double in 0.6-1.1 Gyr. We are viewing the peak epoch of star formation for these protocluster galaxies. However, it appears that extinction of Hα is much greater (up to a factor of 40) in the two ULIRG HAEs compared to the Spiderweb. This may be attributed to different spatial distributions of star formation-nuclear star formation in the HAEs versus extended star formation in accreting satellite galaxies in the Spiderweb. We find extremely luminous mid-IR rotational line emission from warm molecular hydrogen in the Spiderweb Galaxy, with L(H2 0-0 S(3)) = 1.4 × 1044 erg s–1 (3.7 × 1010 L ☉), ~20 times more luminous than any previously known H2 emission galaxy (MOHEG). Depending on the temperature, this corresponds to a very large mass of >9 × 106-2 × 109 M ☉ of T > 300 K molecular gas, which may be heated by the PKS 1138–26 radio jet, acting to quench nuclear star formation. There is >8 times more warm H2 at these temperatures in the Spiderweb than what has been seen in low-redshift (z < 0.2) radio galaxies, indicating that the Spiderweb may have a larger reservoir of molecular gas than more evolved radio galaxies. This is the highest redshift galaxy yet in which warm molecular hydrogen has been directly detected.
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Emonts, B.; Feain, I.; Röttgering, H.; Miley, G.; Seymour, Nick; Norris, R.; Carilli, C.; Villar-Martín, M.; Mao, M.; Sadler, E.; Ekers, R.; van Moorsel, G.; Ivison, R.; Pentericci, L.; Tadhunter, C.; Saikia, D. (2013)The high-redshift radio galaxy MRC 1138−262 (‘Spiderweb Galaxy’; z = 2.16) is one of the most massive systems in the early Universe and surrounded by a dense ‘web’ of proto-cluster galaxies. Using the Australia Telescope ...
Dannerbauer, H.; Lehnert, M.; Emonts, B.; Ziegler, B.; Altieri, B.; De Breuck, C.; Hatch, N.; Kodama, T.; Koyama, Y.; Kurk, J.; Matiz, T.; Miley, G.; Narayanan, D.; Norris, R.; Overzier, R.; Röttgering, H.; Sargent, M.; Seymour, Nick; Tanaka, M.; Valtchanov, I.; Wylezalek, D. (2017)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 ...
Gullberg, B.; Lehnert, M.; de Breuck, C.; Branchu, S.; Dannerbauer, H.; Drouart, G.; Emonts, B.; Guillard, P.; Hatch, N.; Nesvadba, N.; Omont, A.; Seymour, Nick; Vernet, J. (2016)We present 0.5 resolution ALMA detections of the observed 246 GHz continuum, [CI] 3P2→3P1 fine structure line ([CI]2–1), CO(7–6), and H2O lines in the z = 2.161 radio galaxy MRC1138-262, the so-called Spiderweb galaxy. ...