arXiv:0802.3004 [ps, pdf, other] Title: The Redshift Evolution of Wet, Dry, and Mixed Galaxy Mergers from Close Galaxy Pairs in the DEEP2 Galaxy Redshift Survey Authors: Lihwai Lin (1,2), David R. Patton (3), David C. Koo (2), Kevin Casteels (3), Christopher J. Conselice (4), S. M. Faber (2), Jennifer Lotz (5,6), Christopher N. A. Willmer (7), B. C. Hsieh (1), Tzihong Chiueh (8), Jeffrey A. Newman (9), Gregory S. Novak (2), Benjamin J. Weiner (7), Michael C. Cooper (7,10) ((1)ASIAA, (2)UCO/Lick, & UC Santa Cruz, (3)Trent Univ., (4) Univ. of Nottingham, (5) NOAO, (6)Leo Goldberg Fellow, (7)Steward Observatory, Univ. of Arizona, (8)NTU, (9)Univ. of Pittsburgh, (10)Spitzer Fellow) Comments: 11 pages, 8 figures, submitted to ApJ, revised according to the referee's comments License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/ Subjects: Astrophysics (astro-ph) We study the redshift evolution of galaxy pair fractions and merger rates for different types of galaxies using kinematic pairs selected from the DEEP2 Redshift Survey. Parameterizing the evolution of the pair fraction as (1+z)^{m}, we find that the companion rate increases mildly with redshift with m = 0.41+-0.20 for all galaxies with -21 < M_B^{e} < -19. Blue galaxies show slightly faster evolution in the blue companion rate with m = 1.27+-0.35 while red galaxies have had fewer red companions in the past as evidenced by the negative slope m = -0.92+-0.59. We find that at low redshift the pair fraction within the red sequence exceeds that of the blue cloud, indicating a higher merger probability among red galaxies compared to that among the blue galaxies. With further assumptions on the merger time scale and the fraction of pairs that will merge, the galaxy major merger rates for 0.1 < z <1.2 are estimated to be ~10^{-3}h^{3}Mpc^{-3}Gyr^{-1} with a factor of 2 uncertainty. At z ~ 1.1, 68% of mergers are wet, 8% of mergers are dry, and 24% of mergers are mixed, compared to 31% wet mergers, 25% dry mergers, and 44% mixed mergers at z ~ 0.1. The growth of dry merger rates with decreasing redshift is mainly due to the increase in the co-moving number density of red galaxies over time. About 22% to 54% of present-day L^{*} galaxies have experienced major mergers since z ~ 1.2, depending on the definition of major mergers. Moreover, 24% of the red galaxies at the present epoch have had dry mergers with luminosity ratios between 1:4 and 4:1 since z ~ 1. Our results also suggest that the wet mergers and/or mixed mergers may be partially responsible for producing red galaxies with intermediate masses while a significant portion of massive red galaxies is assembled through dry mergers at later times. arXiv:0802.3185 [ps, pdf, other] Title: Limitations of Bayesian Evidence Applied to Cosmology Authors: G. Efstathiou Comments: 5 pages 3 figures submitted to MNRAS License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/ Subjects: Astrophysics (astro-ph) There has been increasing interest in applying Bayesian techniques for model selection (such as Bayesian Evidence) to problems in cosmology. A typical example is in assessing whether observational data favour a cosmological constant over evolving dark energy. In this paper, the example of dark energy is used to illustrate limitations in the application of Bayesian Evidence associated with subjective judgements concerning the choice of model and priors. arXiv:0802.3368 [ps, pdf, other] Title: A comparison of the s- and r-process element evolution in local dwarf spheroidal galaxies and in the Milky Way Authors: Gustavo A. Lanfranchi (1), Francesca Matteucci (2,3), Gabriele Cescutti (2) ((1)Nucleo de Astrofisica Teorica-UNICSUL, Brazil (2) Dipartimento di Astronomia-Universita di Trieste, Italy, (3) I.N.A.F. Osservatorio Astronomico di Trieste, Italy) Comments: 12 pages, 5 figures, accepted for publication in Astronomy & Astrophysics License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/ Subjects: Astrophysics (astro-ph) We study the nucleosynthesis of several neutron capture elements (barium, europium, lanthanum, and yttrium) in local group dwarf spheroidal (dSph) galaxies and in the Milky Way by comparing the evolution of [Ba/Fe], [Eu/Fe], [La/Fe], [Y/Fe], [Ba/Y], [Ba/Eu], [Y/Eu], and [La/Eu] observed in dSph galaxies and in our Galaxy with predictions of detailed chemical evolution models. The models for all dSph galaxies and for the Milky Way are able to reproduce several observational features of these galaxies, such as a series of abundance ratios and the stellar metallicities distributions. The Milky Way model adopts the two-infall scenario, whereas the most important features of the models for the dSph galaxies are the low star-formation rate and the occurrence of intense galactic winds. We predict that the [s-r/Fe] ratios in dSphs are generally different than the corresponding ratios in the Milky Way, at the same [Fe/H] values. This is interpreted as a consequence of the time-delay model coupled with different star formation histories. In particular, the star-formation is less efficient in dSphs than in our Galaxy and it is influenced by strong galactic winds. Our predictions are in very good agreement with the available observational data. The time-delay model for the galactic chemical enrichment coupled with different histories of star formation in different galaxies allow us to succesfully interpret the observed differences in the abundance ratios of s- and r- process elements, as well as of $\alpha$-elements in dSphs and in the Milky Way. These differences strongly suggest that the main stellar populations of these galaxies could not have had a common origin and, consequently, that the progenitors of local dSphs might not be the same objects as the building blocks of our Galaxy. [36] arXiv:0802.3650 [ps, pdf, other] Title: Luminous K-band Selected Quasars from UKIDSS Authors: Natasha Maddox (1 and 2), Paul C. Hewett (1), S. J. Warren (3), S. M. Croom (4) ((1) Institute of Astronomy, Cambridge, (2) Astrophysikalisches Institut Potsdam, (3) Imperial College London, (4) University of Sydney) Comments: 22 pages, 18 figures, accepted for publication in MNRAS. Resolution of Figure 2 has been reduced for astro-ph submission. The complete Table 5 can be found at this http URL License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/ Subjects: Astrophysics (astro-ph) The largest K-band flux-limited sample of luminous quasars to date has been constructed from the UKIDSS Large Area Survey Early Data Release, covering an effective area of 12.8 deg^2. Exploiting the K-band excess of all quasars with respect to foreground stars, including quasars experiencing dust reddening and objects with non-standard SEDs, a list of targets suitable for spectroscopic follow-up observations with the AAOmega multi-object spectrograph is constructed, resulting in more than 200 confirmed AGN. KX-selection successfully identifies as quasar candidates objects that are excluded from the SDSS quasar selection algorithm due to their colours being consistent with the stellar locus in optical colour space (with the space density of the excluded objects agreeing well with results from existing completeness analyses). Nearly half of the KX-selected quasars with K<17.0 at z<3 are too faint in the i-band to have been targeted by the SDSS quasar selection algorithm, revealing a large population of quasars with red i-K colours. The majority of these objects have significant amounts of host galaxy light contributing to their K-band magnitudes, consistent with previous predictions. The remaining objects are morphologically stellar and have colours consistent with quasars experiencing SMC-type reddening with 0.10