Obscured Star Formation in Intermediate-Density Environments: A Spitzer Study of the Abell 901/902 Supercluster
Gallazzi, Anna; Bell, Eric F.; Wolf, Christian;Gray, Meghan E.; Papovich, Casey; Barden, Marco;Peng, Chien Y.; Meisenheimer, Klaus;Heymans, Catherine; van Kampen, Eelco;Gilmour, Rachel; Balogh, Michael;McIntosh, Daniel H.; Bacon, David; Barazza, Fabio D.;Böhm, Asmus; Caldwell, John A. R.; Häußler, Boris;Jahnke, Knud; Jogee, Shardha; Lane, Kyle;Robaina, Aday R.; Sanchez, Sebastian F.;Taylor, Andy; Wisotzki, Lutz; Zheng, Xianzhong. Obscured Star Formation in Intermediate-Density Environments: A Spitzer Study of the Abell 901/902 Supercluster. The Astrophysical Journal. 2009, Vol. Volume 690, Issue 2, pp. 1883-1900 (2009)., p. -2009.
We explore the amount of obscured star formation as a function of
environment in the Abell 901/902 (A901/902) supercluster at z = 0.165 in
conjunction with a field sample drawn from the A901 and CDFS fields,
imaged with the Hubble Space Telescope as part of the Space Telescope
A901/902 Galaxy Evolution Survey and Galaxy Evolution from Morphology
and Spectral Energy Distributions (SEDs) Survey. We combine the COMBO-17
near-UV/optical SED with Spitzer 24 μ photometry to estimate both the
unobscured and obscured star formation in galaxies with M <SUB>*</SUB>
> 10<SUP>10</SUP> M <SUB>sun</SUB>. We find that the star formation
activity in massive galaxies is suppressed in dense environments, in
agreement with previous studies. Yet, nearly 40% of the star-forming
(SF) galaxies have red optical colors at intermediate and high
densities. These red systems are not starbursting; they have star
formation rates (SFRs) per unit stellar mass similar to or lower than
blue SF galaxies. More than half of the red SF galaxies have low
infrared-to-ultraviolet (IR-to-UV) luminosity ratios, relatively high
Sérsic indices, and they are equally abundant at all densities.
They might be gradually quenching their star formation, possibly but not
necessarily under the influence of gas-removing environmental processes.
The other gsim40% of the red SF galaxies have high IR-to-UV luminosity
ratios, indicative of high dust obscuration. They have relatively high
specific SFRs and are more abundant at intermediate densities. Our
results indicate that while there is an overall suppression in the SF
galaxy fraction with density, the small amount of star formation
surviving the cluster environment is to a large extent obscured,
suggesting that environmental interactions trigger a phase of obscured
star formation, before complete quenching.
We explore the amount of obscured star formation as a function of
environment in the Abell 901/902 (A901/902) supercluster at z = 0.165 in
conjunction with a field sample drawn from the A901 and CDFS fields,
imaged with the Hubble Space Telescope as part of the Space Telescope
A901/902 Galaxy Evolution Survey and Galaxy Evolution from Morphology
and Spectral Energy Distributions (SEDs) Survey. We combine the COMBO-17
near-UV/optical SED with Spitzer 24 μ photometry to estimate both the
unobscured and obscured star formation in galaxies with M <SUB>*</SUB>
> 10<SUP>10</SUP> M <SUB>sun</SUB>. We find that the star formation
activity in massive galaxies is suppressed in dense environments, in
agreement with previous studies. Yet, nearly 40% of the star-forming
(SF) galaxies have red optical colors at intermediate and high
densities. These red systems are not starbursting; they have star
formation rates (SFRs) per unit stellar mass similar to or lower than
blue SF galaxies. More than half of the red SF galaxies have low
infrared-to-ultraviolet (IR-to-UV) luminosity ratios, relatively high
Sérsic indices, and they are equally abundant at all densities.
They might be gradually quenching their star formation, possibly but not
necessarily under the influence of gas-removing environmental processes.
The other gsim40% of the red SF galaxies have high IR-to-UV luminosity
ratios, indicative of high dust obscuration. They have relatively high
specific SFRs and are more abundant at intermediate densities. Our
results indicate that while there is an overall suppression in the SF
galaxy fraction with density, the small amount of star formation
surviving the cluster environment is to a large extent obscured,
suggesting that environmental interactions trigger a phase of obscured
star formation, before complete quenching.