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ABSTRACT: We study the IR properties of galaxies in the cluster MS 1054-03 at z = 0.83 by combining MIPS 24 μm data with spectra of more than 400 galaxies and a very deep K-band-selected catalog. Nineteen IR cluster members are selected spectroscopically, and an additional 15 are selected by their photometric redshifts. We derive the IR luminosity function of the cluster and find strong evolution compared to the similar-mass Coma Cluster. The best-fitting Schechter function gives L = 11.49 L☉ with a fixed faint-end slope, about 1 order of magnitude larger than that in Coma. The rate of evolution of the IR luminosity from Coma to MS 1054-03 is consistent with that found in field galaxies, and it suggests that some internal mechanism, e.g., the consumption of the gas fuel, is responsible for the general decline of the cosmic SFR in different environments. The mass-normalized integrated SFR within 0.5R200 in MS 1054-03 also shows evolution compared with other rich clusters at lower redshifts, but the trend is less conclusive if the mass selection effect is considered. A nonnegligible fraction (13% ± 3%) of cluster members are forming stars actively, and the overdensity of IR galaxies is about 20 compared to the field. It is unlikely that clusters only passively accrete star-forming galaxies from the surrounding fields and have their star formation quenched quickly afterward; instead, many cluster galaxies still have large amounts of gas, and their star formation may be enhanced by the interaction with the cluster.
The Astrophysical Journal 12/2008; 664(1):181. · 6.02 Impact Factor
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ABSTRACT: Using mid-IR and optical data, we deduce the total infrared (IR) luminosities of galaxies in the Coma Cluster and present their IR luminosity function (LF). The shape of the overall Coma IR LF does not show significant differences from the IR LFs of the general field, which indicates the general independence of global galaxy star formation from environment up to densities ~40 times greater than in the field (we cannot test such independence above LIR ≈ 1044 ergs s-1). However, a shallower faint-end slope and a smaller L are found in the core region (where the densities are still higher) compared to the outskirt region of the cluster, and most of the brightest IR galaxies are found outside the core region. The IR LF in the NGC 4839 group region does not show any unique characteristics. By integrating the IR LF, we find a total star formation rate in the cluster of about 97.0 M☉ yr-1. We also studied the contributions of early- and late-type galaxies to the IR LF. The late-type galaxies dominate the bright end of the LF, and the early-type galaxies, although only making up a small portion (≈15%) of the total IR emission of the cluster, contribute greatly to the number counts of the LF at LIR < 1043 ergs s-1.
The Astrophysical Journal 12/2008; 639(2):827. · 6.02 Impact Factor
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Brent A. Buckalew,
Henry A. Kobulnicky,
Jonathan M. Darnel,
Elisha Polomski,
Robert D. Gehrz,
Roberta M. Humphreys,
Charles E. Woodward, Joannah L. Hinz,
C. W. Engelbracht,
Karl D. Gordon, [......],
P. G. Pérez-González,
George H. Rieke,
S. P. Willner,
M. L. Ashby,
P. Barmby,
M. A. Pahre,
T. L. Roellig,
Nick Devereux,
Jacco Th. Loon,
and B. Brandl
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ABSTRACT: We present ultraviolet, optical, near-infrared, Spitzer mid-infrared, and radio images of 14 radio-selected objects in M33. These objects are thought to represent the youngest phase of star cluster formation. We have detected the majority of cluster candidates in M33 at all wavelengths. From the near-IR images, we derived ages 2-10 Myr, KS-band extinctions (A) of 0-1 mag, and stellar masses of 103-104 M☉. We have generated spectral energy distributions (SEDs) of each cluster from 0.1 to 160 μm. From these SEDs, we have modeled the dust emission around these star clusters to determine the dust masses (1-103 M☉) and temperatures (40-90 K) of the clusters' local interstellar medium. Extinctions derived from the JHKS, Hα, and UV images are similar to within a factor of 2 or 3. These results suggest that 11 of the 14 radio-selected objects are optically visible young star clusters with a surrounding H II region, that 2 are background objects, possibly active galactic nuclei (AGNs), and that 1 is a Wolf-Rayet star with a surrounding H II region.
The Astrophysical Journal Supplement Series 12/2008; 162(2):329. · 13.46 Impact Factor
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Brent A. Buckalew,
Henry A. Kobulnicky,
Jonathan M. Darnel,
Elisha Polomski,
Robert D. Gehrz,
Roberta M. Humphreys,
Charles E. Woodward, Joannah L. Hinz,
C. W. Engelbracht,
Karl D. Gordon, [......],
P. G. Perez-Gonzalez,
George H. Rieke,
S. P. Willner,
M. L. N. Ashby,
P. Barmby,
M. A. Pahre,
T. L. Roellig,
Nick Devereux,
Jacco Th. van Loon,
B Brandl
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ABSTRACT: We present ultraviolet, optical, near-infrared, Spitzer mid-infrared, and radio images of 14 radio-selected objects in M 33. These objects are thought to represent the youngest phase of star cluster formation. We have detected the majority of cluster candidates in M 33 at all wavelengths. From the near-IR images, we derived ages 2-10 Myr, K_S-band extinctions (A_K_S) of 0-1 mag, and stellar masses of 10^3-10^4 M_solar. We have generated spectral energy distributions (SEDs) of each cluster from 0.1 micron to 160 microns. From these SEDs, we have modeled the dust emission around these star clusters to determine the dust masses (1-10^3 M_solar) and temperatures (40-90 K) of the clusters' local interstellar medium. Extinctions derived from the JHK_S, Halpha, and UV images are similar to within a factor of 2 or 3. These results suggest that eleven of the fourteen radio-selected objects are optically-visible young star clusters with a surrounding H II region, that two are background objects, possibly AGN, and that one is a Wolf-Rayet star with a surrounding H II region. Comment: 57 pages total; 20 figures; 3 tables under review by ApJS; first review complete
09/2005;
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Oliver Krause,
George H Rieke,
Stephan M Birkmann,
Emeric Le Floc'h,
Karl D Gordon,
Eiichi Egami,
John Bieging,
John P Hughes,
Erick T Young, Joannah L Hinz,
Sascha P Quanz,
Dean C Hines
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ABSTRACT: Two images of Cassiopeia A obtained at 24 micrometers with the Spitzer Space Telescope over a 1-year time interval show moving structures outside the shell of the supernova remnant to a distance of more than 20 arc minutes. Individual features exhibit apparent motions of 10 to 20 arc seconds per year, independently confirmed by near-infrared observations. The observed tangential velocities are at roughly the speed of light. It is likely that the moving structures are infrared echoes, in which interstellar dust is heated by the explosion and by flares from the compact object near the center of the remnant.
Science 07/2005; 308(5728):1604-6. · 31.20 Impact Factor
