Bulletin of the American Physical Society
2012 Annual Fall Meeting of the APS Prairie Section
Volume 57, Number 14
Thursday–Saturday, November 8–10, 2012; Lawrence, Kansas
Session D1: Astrophysics, Cosmology and Space Science II |
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Chair: Barbara Anthony-Twarog, University of Kansas Room: Oread Hotel Hancock Room |
Friday, November 9, 2012 4:15PM - 4:27PM |
D1.00001: Measuring the Red Sequence Slope in a Distant Galaxy Cluster Erin Schultz, Gregory Rudnick Our project goal is to constrain the possible stellar mass dependence of galaxy ages for red sequence galaxies. We use the Y, J, and K-band data collected from the Very Large Telescope in Chile of the z = 1.62 galaxy cluster XMM-LSS J02182-051020. This spectroscopically confirmed galaxy cluster is one of the only known massive clusters at an epoch close to the time when stars stopped forming within red sequence galaxies. For red sequence galaxies, which have little recent star formation and little dust, the color is an indicator of the luminosity weighted age of the stars. This is in turn correlated to the last epoch of significant star formation. At the same time, the mass of such a galaxy is correlated to its magnitude. The more stars a galaxy contains, the more massive and brighter the galaxy. The slope of the red sequence in color-magnitude space, therefore, gives an indication of the dependence of galaxy age on stellar mass. We use the age-sensitive Y-J color and measure a slope of zero for the red sequence in Y-J vs. J. We interpret this to mean that the age does not depend strongly on the mass of the galaxy. If time allows, we will present the limits on the slope of the color-magnitude relation and will discuss what limits this corresponds to on the age dependence with mass. [Preview Abstract] |
Friday, November 9, 2012 4:27PM - 4:39PM |
D1.00002: The Role of Clusters and Groups in Stopping Gas Accretion onto Galaxies Gregory Rudnick, Pascale Jablonka, John Moustakas Despite decades of work, it is still unclear whether a galaxy's properties are affected by environment or whether they are determined solely by the galaxy's mass. I will present new results that shed light on the key question of how the gas supplies of galaxies may be altered by dense environments. We use a stellar mass selected sample consisting of hundreds of cluster, group, and field galaxies at $0.4 < z < 0.8$ with multi-wavelength imaging and deep spectroscopy. We identify galaxies whose light is dominated by old stellar populations and, contrary to expectations, we find that these ``old'' galaxies at intermediate redshift have a high likelihood of hosting weak [OII] emission. In contrast, analogously old galaxies in clusters and groups are significantly less likely to have activity. Our results imply that the cluster and group environments are effective at either stripping out gas from deep in the potential wells of galaxies or at cutting off their fuel supply of fresh new gas. Our work is possible because we probe a large number of clusters (not available in DEEP2 or COSMOS) as well as coeval group and field galaxies, and use deep Spitzer observations to search for dust-obscured star formation. [Preview Abstract] |
Friday, November 9, 2012 4:39PM - 4:51PM |
D1.00003: Constraining dark energy models using Hubble parameter, Supernova, and BAO Data Muhammad Farooq We use Hubble parameter versus redshift data, Baryon Acoustic Oscillation (BAO) data and Supernova Type Ia (SNeIa) data to place constraints on model parameters of one constant two one time-evolving dark energy cosmological models. These constraints are we got are pretty much consistent with (through not as restrictive as) those derived by Yun {\&} Ratra (2011). The reason for that is the systematic errors in new BAO and SNeIa data are more as compared to the old data Yun {\&} Ratra (2011). A joint analysis of the Hubble parameter data with more restrictive baryon acoustic oscillation peak length scale and supernova Type Ia apparent magnitude data favors a spatially-flat cosmological model currently dominated by a time-independent cosmological constant but does not exclude slow time-varying dark energy. [Preview Abstract] |
Friday, November 9, 2012 4:51PM - 5:03PM |
D1.00004: Forecasting cosmological parameter constraints from near-future space-based galaxy surveys Anatoly Pavlov, Lado Samushia, Bharat Ratra The next generation of space-based galaxy surveys are expected to measure the growth rate of structure to about a percent level over a range of redshifts. The rate of growth of structure as a function of redshift depends on the behavior of dark energy and so can be used to constrain parameters of dark energy models. In this work we investigate how well these future data will be able to constrain the time dependence of the dark energy density. We consider parameterizations of the dark energy equation of state, such as XCDM and $\omega$CDM, as well as a consistent physical model of time-evolving scalar field dark energy, $\phi$CDM. We show that if the standard, specially-flat cosmological model is taken as a fiducial model of the Universe, these near-future measurements of structure growth will be able to constrain the time-dependence of scalar field dark energy density to a precision of about 10\%, which is almost an order of magnitude better than what can be achieved from a compilation of currently available data sets. [Preview Abstract] |
Friday, November 9, 2012 5:03PM - 5:15PM |
D1.00005: A Correlation of Magnitudes, Color and Redshift in Cosmologically Distant Type 1a Supernovae Gopolang Mohlabeng, John Ralston We independently explore the Union 2.1 data set (Supernova Cosmology Project) of 580 type 1a supernovae. We find a correlation of very high statistical significance between supernova color $\times$ redshift and distance modulus residuals relative to the standard cosmological model. We find a Pearson correlation coefficient $r_{SN} =-0.521$, which is more than 13 standard deviations ($\sigma$) away from the mean obtained by Monte-Carlo simulations with random data shuffling. We find that adding one parameter to the standard magnitude vs redshift relation improves the value of $\chi ^{2}$ by more than 50 units. The updated Dark Energy and matter density parameters, assuming a flat universe are $\Omega _\Lambda =0.74\pm 0.013$ and $\Omega _m =0.260\pm 0.013$. The trend of the correlation is that distant supernovae become redder as a function of redshift by a rule which cannot be fit by the standard Cosmology. [Preview Abstract] |
Friday, November 9, 2012 5:15PM - 5:27PM |
D1.00006: Formation and Origin of Rotation Equations for Planetary and Stellar Bodies Stewart Brekke Planets began with a planetary core, slowly rotating, with rings of molten material orbiting it. The gravitational attraction of the core caused the orbits of the rings of material to decay and the rings tangentially collided with the planetary core attaching to the core and transferring the orbital momentum of each of the rings to the planetary core thereby increasing the rotational speed of the newly formed planet. The equation for this phenomenon is as follows: $ (1/2I\omega^2)_{core}+ (1/2I\omega^2)_{ring1}+...+(1/2I\omega^2)_{ringn}= (1/2I\omega^2)_{planet}$. Stars began with a slowly rotating stellar core orbited by rings and partial rings of primarily hydrogen in motion. As the gravitational attraction of the stellar core caused the orbits of the rings and partial rings to decay the rings and partial rings of hydrogen tangentially collided with the rotating stellar core attaching and transferring their orbital momentum to the stellar cores thereby causing a speeded up rotation of the newly formed star. The equation for this stellar formation and origin of rotation is as follows: $(1/2I\omega^2)_{stellar core} + (1/2I\omega^2)_{ring 1}+...+(1/2I\omega^2)_{ring n} = (1/2I\omega^2)_{star}$. [Preview Abstract] |
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