Anze Slosar

Cosmological parameters from combining the Lyman-α forest with CMB, galaxy clustering and SN constraints

We combine the Ly-? forest power spectrum (LYA) from the Sloan Digital Sky Survey (SDSS) and high resolution spectra with cosmic microwave background (CMB) including three-year WMAP, and supernovae (SN) and galaxy clustering constraints to derive new constraints on cosmological parameters. The existing LYA power spectrum analysis is supplemented by constraints on the mean flux decrement derived using a principle component analysis for quasar continua, which improves the LYA constraints on the linear power. We find some tension between the WMAP3 and LYA power spectrum amplitudes, at the ~2? level, which is partially alleviated by the inclusion of other observations: we find ?8 = 0.85 ? 0.02 compared to ?8 = 0.80 ? 0.03 without LYA. For the slope, we find ns = 0.965 ? 0.012. We find no evidence for the running of the spectral index in the combined analysis, dn/dlnk = ?(1.5 ? 1.2) ? 10?2, in agreement with inflation. The limits on the sum of neutrino masses are significantly improved: at 95% ( 1.3 (95% c.l.). Assuming a thermalized fourth neutrino, we find ms<0.26?eV at 95% c.l. and such a neutrino cannot be an explanation for the LSND results. In the limits of massless neutrinos, we obtain the effective number of neutrinos N?eff = 5.3?0.6+0.4?1.7+2.1?2.5+3.8 and N?eff = 3.04 is allowed only at 2.4 sigma. The constraint on the dark energy equation of state is w = ?1.04 ? 0.06. The constraint on curvature is ?k = ?0.003 ? 0.006. Cosmic strings limits are G?<2.3 ? 10?7 at 95% c.l. and correlated isocurvature models are also tightly constrained.

Galaxy Zoo: the dependence of morphology and colour on environment

We analyse the relationships between galaxy morphology, colour, environment and stellar mass using data for over 105 objects from Galaxy Zoo, the largest sample of visually classified morphologies yet compiled. We conclusively show that colour and morphology fractions are very different functions of environment. Both colour and morphology are sensitive to stellar mass. However, at fixed stellar mass, while colour is also highly sensitive to environment, morphology displays much weaker environmental trends. Only a small part of both the morphology–density and colour–density relations can be attributed to the variation in the stellar-mass function with environment. Galaxies with high stellar masses are mostly red in all environments and irrespective of their morphology. Low stellar-mass galaxies are mostly blue in low-density environments, but mostly red in high-density environments, again irrespective of their morphology. While galaxies with early-type morphology do always have higher red fractions, this is subdominant compared to the dependence of red fraction on stellar mass and environment. The colour–density relation is primarily driven by variations in colour fractions at fixed morphology, in particular the fraction of spiral galaxies that have red colours, and especially at low stellar masses. We demonstrate that our red spirals primarily include galaxies with true spiral morphology, and that they constitute an additional population to the S0 galaxies considered by previous studies. We clearly show there is an environmental dependence for colour beyond that for morphology. The environmental transformation of galaxies from blue to red must occur on significantly shorter time-scales than the transformation from spiral to early-type. We also present many of our results as functions of the distance to the nearest galaxy group. This confirms that the environmental trends we present are not specific to the manner in which environment is quantified, but nevertheless provides plain evidence for an environmental process at work in groups. However, the properties of group members show little dependence on the total mass of the group they inhabit, at least for group masses ≳1013M⊙. Before using the Galaxy Zoo morphologies to produce the above results, we first quantify a luminosity-, size- and redshift-dependent classification bias that affects this data set, and probably most other studies of galaxy population morphology. A correction for this bias is derived and applied to produce a sample of galaxies with reliable morphological-type likelihoods, on which we base our analysis.

Galaxy Zoo Green Peas: discovery of a class of compact extremely star-forming galaxies

We investigate a class of rapidly growing emission line galaxies, known as “Green Peas,” first noted by volunteers in the Galaxy Zoo project because of their peculiar bright green colour and small size, unresolved in SDSS imaging. Their appearance is due to very strong optical emission lines, namely [O III] �5007 ˚ A, with an unusually large equivalent width of up to �1000 ˚ A. We discuss a well-defined sample of 251 colour-selected ob jects, most of which are strongly star forming, although there are some AGN interlopers including 8 newly discovered Narrow Line Seyfert 1 galaxies. The star-forming Peas are low mass galaxies (M� 10 8.5 10 10 M⊙) with high star formation rates (� 10 M⊙yr −1 ), low metallicities (log[O/H] + 12 �8.7) and low reddening (E(B V) 6 0.25) and they reside in low density environments. They have some of the highest specific star for mation rates (up to � 10 −8 yr −1 ) seen in the local Universe, yielding doubling times for their stellar mass of hundreds of Myrs. The few star-forming Peas with HST imaging appear to have several clumps of bright star-forming regions and low surface density features that may indicate recent or ongoing mergers. The Peas are similar in size, mass, luminosity and metallicity to Luminous Blue Compact Galaxies. They are also similar to high redshift UV-luminous galaxies, e.g., Lymanbreak galaxies and Lyman-� emitters, and therefore provide a local laboratory with which to study the extreme star formation processes that occur in high-redshift galaxies. Studying starbursting galaxies as a function of redshift is essential to u nderstanding the build up of stellar mass in the Universe.

Baryon Acoustic Oscillations in the Ly-α forest of BOSS quasars

We report a detection of the baryon acoustic oscillation (BAO) feature in the three-dimensional correlation function of the transmitted flux fraction in the \Lya forest of high-redshift quasars. The study uses 48,640 quasars in the redshift range

Galaxy Zoo: reproducing galaxy morphologies via machine learning★

2.1\le z \le 3.5

Inflation and WMAP three year data: Features are still present

from the Baryon Oscillation Spectroscopic Survey (BOSS) of the third generation of the Sloan Digital Sky Survey (SDSS-III). At a mean redshift

Sterile neutrinos in light of recent cosmological and oscillation data: a multi-flavor scheme approach

z=2.3

Cosmological constraints from type Ia supernovae peculiar velocity measurements

, we measure the monopole and quadrupole components of the correlation function for separations in the range

Present bounds on the relativistic energy density in the Universe from cosmological observables

20\hMpc<r<200\hMpc

High sensitivity measurements of the CMB power spectrum with the extended Very Small Array

. A peak in the correlation function is seen at a separation equal to