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University of Massachusetts Amherst

Evolution

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Full-Text Articles in Physical Sciences and Mathematics

Quest For Cosmos Submillimeter Galaxy Counterparts Using Carma And Vla: Identifying Three High-Redshift Starburst Galaxies, V. Smolčić, F. Navarrete, M. Aravena, O. Ilbert, M. S. Yun, K. Sheth, M. Salvato, H. J. Mccracken, Diener C., I. Aretxaga, D. A. Riechers, A. Finoguenov, F. Bertoldi, P. Capak, D. Hughes, A. Karim, E. Schinnerer, N. Z. Scoville, Grant Wilson Jan 2012

Quest For Cosmos Submillimeter Galaxy Counterparts Using Carma And Vla: Identifying Three High-Redshift Starburst Galaxies, V. Smolčić, F. Navarrete, M. Aravena, O. Ilbert, M. S. Yun, K. Sheth, M. Salvato, H. J. Mccracken, Diener C., I. Aretxaga, D. A. Riechers, A. Finoguenov, F. Bertoldi, P. Capak, D. Hughes, A. Karim, E. Schinnerer, N. Z. Scoville, Grant Wilson

Grant Wilson

We report on interferometric observations at 1.3 mm at 2"-3" resolution using the Combined Array for Research in Millimeter-wave Astronomy (CARMA). We identify multi-wavelength counterparts of three submillimeter galaxies (SMGs; F(1mm)>5.5 mJy) in the COSMOS field, initially detected with MAMBO and AzTEC bolometers at low, ~10"-30", resolution. All three sources -- AzTEC/C1, Cosbo-3 and Cosbo-8 -- are identified to coincide with positions of 20 cm radio sources. Cosbo-3, however, is not associated with the most likely radio counterpart, closest to the MAMBO source position, but that further away from it. This illustrates the need for intermediate-resolution (~2") mm-observations to …


Morphological Transformation From Galaxy Harassment, B Moore, G Lake, N Katz Jan 1998

Morphological Transformation From Galaxy Harassment, B Moore, G Lake, N Katz

Astronomy Department Faculty Publication Series

Galaxy morphologies in clusters have undergone a remarkable transition over the past several billion yr. Distant clusters at z ~ 0.4 are filled with small spiral galaxies, many of which are disturbed and show evidence of multiple bursts of star formation. This population is absent from nearby clusters, where spheroidals comprise the faint end of the luminosity function. Our numerical simulations follow the evolution of disk galaxies in a rich cluster resulting from encounters with brighter galaxies and the cluster's tidal field, or "galaxy harassment." After a bursting transient phase, they undergo a complete morphological transformation from "disks" to "spheroidals." …


The Formation Of Quasars In Low-Luminosity Hosts Via Galaxy Harassment, G Lake, N Katz, B Moore Jan 1998

The Formation Of Quasars In Low-Luminosity Hosts Via Galaxy Harassment, G Lake, N Katz, B Moore

Astronomy Department Faculty Publication Series

We have simulated disk galaxies undergoing continual bombardment by other galaxies in a rich cluster. "Galaxy harassment" leads to dramatic evolution of smaller disk galaxies and provides an extremely effective mechanism for fueling a central quasar. Within a few billion years after a small disk galaxy enters the cluster environment, up to 90% of its gas can be driven into the inner 500 pc. Up to half of the mass can be transferred in a burst lasting just 100-200 Myr. This transport of gas to the center of galaxy is far more efficient than any mechanism proposed before. Galaxy harassment …


The Effect Of The Galactic Spheroid On Globular Cluster Evolution, C Murali, Md Weinberg Jan 1997

The Effect Of The Galactic Spheroid On Globular Cluster Evolution, C Murali, Md Weinberg

Astronomy Department Faculty Publication Series

We study the combined effects of relaxation, tidal heating and binary heating on globular cluster evolution, exploring the physical consequences of external effects and examining evolutionary trends in the MilkyWay population. Our analysis demonstrates that heating on circular and low-eccentricity orbits can dominate cluster evolution. The results also predict rapid evolution on eccentric orbits either due to strong relaxation caused by the high densities needed for tidal limitation or due to efficient bulge shocking of low density clusters. The combination of effects leads to strong evolution of the population as a whole. For example, within the solar circle, tidally-limited 105M⊙ …


Evolution Of The Galactic Globular Cluster System, C Murali, Md Weinberg Jan 1997

Evolution Of The Galactic Globular Cluster System, C Murali, Md Weinberg

Astronomy Department Faculty Publication Series

We study the dynamical evolution of disk and halo globular clusters in the Milky Way using a series of Fokker-Planck calculations combined with parametric statistical models. Our sample of 113 clusters with velocity data is predicted to descend from an initial population of 250 clusters, implying more than a factor of two decrease in population size due to evolution. Approximately 200 of these clusters are in a halo component and 50 in a disk component. The estimated initial halo population follows a coreless R−3.38 density profile in good agreement with current estimates for the distribution of halo field stars. The …