Аннотация
It has yet to be established whether the properties of the gas in distant
protocluster galaxies are significantly affected by their environment as they
are in galaxies in local clusters. Through a deep, 64 hours of effective
on-source integration with the ATCA, we discovered a very massive,
M_mol=2.0+-0.2x10^11 M_sun, very extended, ~40 kpc, CO(1-0)-emitting disk in
the protocluster surrounding the radio galaxy, MRC1138-262. The galaxy, at a
redshift z_CO=2.1478, is a clumpy massive disk galaxy, M_star~5x10^11 M_sun,
which lies 300 kpc in projection from MRC1138-262 and is a known H-alpha
emitter, HAE229. The bulk of the CO emission shows a kinematic gradient along
the major axis of the disk, consistent with rotation. A significant fraction of
the CO emission lies outside of the UV/optical emitting galaxy and the galaxy
has a molecular gas fraction, f_mol~30%. HAE229 follows the relation of normal
field star-forming galaxies between star-formation rate and molecular gas mass.
HAE229 is the first CO(1-0) detection of an ordinary, star-forming galaxy in a
high-redshift protocluster and only the third robust CO(1-0) detection of an
H-alpha emitting galaxy in an high-z overdensity. We compare a sample of
cluster members at z>0.4 that are detected in low-order CO transitions with a
similar sample of sources drawn from the field. We confirm recent findings that
the CO-luminosity and FWHM are correlated in dusty starbursts and show that
this relation is valid for normal high-z galaxies as well as those in
overdensities. We do not find a clear dichotomy in the integrated
Schmidt-Kennicutt relation for protocluster and field galaxies. Not finding any
environmental dependence in the molecular gas content or star-formation
efficiency of galaxies, suggests that environmentally-specific processes such
as ram pressure stripping are not operating efficiently in high-z
(proto)clusters. (abridged)
Описание
[1701.05250] The implications of the surprising existence of a large, massive CO disk in a distant protocluster
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