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Meetings & Social Progam

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Sunday evening drinks

An number of people have planned to meet for drinks at the Yankee Doodle Tap Room on Sunday evening. The get-together is completely informal, and anyone is welcome to join.
Location: Yankee Doodle Tap Room (The lounge at the Nassau Inn)

MARVELS lunch meeting

The MARVELS survey group will hold a lunch meeting on Monday (July 27).
Location: Frist, Class of '52 room

Collaboration Council Dinner

The member of the Collaboration Council will meet for dinner and drinks on Monday evening (July 27).
Location: Triumph Brewery

MC & BPG lunch meeting

The Management Committee and Brazilian Participation Group will hold a lunch meeting on Tuesday (July 28).
Location: Peyton Hall, rm 140

BOSS Spectro pipeline lunch meeting

The BOSS spectro pipeline group will hold a lunch meeting on Tuesday (July 28) from 1:30pm to 2:30pm.
Location: Peyton Hall, Dome Room

Banquet

The banquet will be held on Tuesday evening (July 28) on the top floor of Fine Hall. If you indicated on your registration form that you would be attending the banquet, payment is being handled by Princeton University Conference Services (they are also handling on campus accomodation at Scully Hall).
Location: Fine Hall (top floor)

Change Control Board lunch meeting

The Change Control Board will hold a lunch meeting on Wednesday (July 29) from 1:00pm to 2:30pm.
Location: Peyton Hall, Dome Room

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Posters

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Note to presenters:

  Our poster boards are 30in x 40in (75cm x 100cm), and will be supported on easels. You'll be free to orient the long side of the board vertically or horizontally.

14 posters submitted

(Listed alphabetically by author's surname)

Stellar population models to help APOGEE target selection

Leo Girardi, Osservatorio Astronomico di Padova

(Authors: L. Girardi, B. Rossetto, R. Ogando, L. da Costa, for the Brazilian Participation Group) One of the greatest challenges of APOGEE is the definition of an efficient target selection scheme, where relying only on the 2MASS photometry, one needs to maximize the sampling of giants across the entire Milky Way, avoiding as much as possible the nearby dwarfs as well as biases in the final metallicity distributions. In this poster we illustrate the predictions of TRILEGAL population models for the distribution of stellar parameters in 2MASS color-magnitude and color-color diagrams. We demonstrate that the predicted giant/dwarf ratios are in good agreement with those observed by RAVE (for H<12 and |b|>25 deg) and SEGUE (for H>13) as a function of 2MASS H, J-Ks, and galactic coordinates. Then, for a few selected subsamples of the mock data, we compare the "real" and "observed" metallicity distributions so as to illustrate the biases expected in a spectroscopic survey. The models are made available in the hope that they can help in the definition of APOGEE target selection.

MAX: a Massive compression of chi2 for stellar spectral fitting

Paula Jofre Pfeil, Max Planck Institute for Astrophysics

MAX is an algorithm to estimate multiple parameters from stellar spectra, like, e.g. effective temperature, surface gravity and metallicity. It is based on an optimal compression of the dataset, where the information about the parameters is lossless. The advantage of using the compressed data set is the speed of the analysis, finding the maximum of the likelihood in a grid of models of 300 000 elements in 3 milliseconds. We introduce here MAX as an alternative method to analyze SEGUE spectra.

New flux-calibrated model Lick indices for stellar populations

Jonas Johansson, Institute of Cosmology and Gravitation, University of Portsm

Stellar population models of Lick absorption line indices are a key tool for the analysis of galaxy absorption spectra and the derivation of fundamental galaxy properties such as formation age and alpha/Fe ratio. The Lick stellar library was however not flux-calibrated and models based on this library need to be corrected for calibration offsets when being compared to galaxy data. This problem is critical for SDSS data and in particular for SDSS-III where calibration stars are not accessible for the relevant redshifts. It is therefore important to have models based on flux-calibrated stellar libraries. To this end we have constructed new models of absorption line indices based on modern empirical stellar libraries (e.g. MILES). The new models are flux-calibrated versions of the Thomas, Maraston & Bender (2003) models which include the dependence on variable element abundance ratios, specifically accounting for non solar ratios such as those derived in local elliptical galaxies and SDSS LRGs. We analyze model systematics caused by different libraries and stellar evolutionary tracks. We find that uncertainties affect somewhat the derived formation ages, but the alpha/Fe ratios, hence the inferred formation timescales, are robust.

The Baryonic Acoustic Feature and Large-Scale Clustering of the SDSS LRG Sample

Eyal Kazin, New York University

We examine the correlation function of the Sloan Digital Sky Survey (SDSS) Luminous Red Galaxy sample at large scales (60 < s < 400 Mpc/h) using the final data release (DR7). We demonstrate that the wide baryonic acoustic peak and strong large-scale signal are consistent with Lambda-CDM at the 1.5-sigma level. Fitting data to a non-linear redshift space model we constrain the peak position at s_p = 102.8 ± 3.6 Mpc/h when examining radii range 60 < s < 150 Mpc/h. The uncertainties are 1-sigma values measured from mock catalogs. Not to be confused with the comoving sound horizon scale at the baryon drag epoch r_s(z_d), this redshift space distance s_p is related to r_s after taking into account matter clustering non-linearities, redshift distortions and galaxy clustering bias. We caution that the s_p value is sensitive to the radii range in analysis used, e.g, using a smaller range of 60 < s < 135 Mpc/h we obtain s_p = 105.8 ± 3.6 Mpc/h. Mock catalogs show that the probability that a DR7-sized sample would not have an identifiable peak is at least ~10%. We use the observed s_p to constrain the distance measure D_V=((1+z)^2 D_A^2 cz/H(z))^(1/3). We find r_s/D_V(z=0.277) = 0.1383 ± 0.0048. This result is in excellent agreement with Percival et. al (2009, in prep) who examine roughly the same data set but use a different analysis on the power spectrum.

Description and Status of the 0.8m Southern Utah Observatory

David Kieda, University of Utah Department of Physics and Astronomy

In this poster presentations we describe the site characteristics and status of the 0.8m Southern Utah Observatory (SUO), currently under construction at Frisco Peak , Utah (38.5 N, 113.28 W, 2940 m a.s.l). This site was selected after an extensive site survey and characterization carried out at multiple high altitude sites across southern Utah from 2007-2008. The Frisco Peak site is a high altitude desert site with better than 1” atmospheric seeing in the V-band, and V band sky darkness better than 22 mag/sq arc sec. The Frisco Peak site has existing internet, power, and nearby year-round road access. Construction of the SUO telescope site began in Spring 2009 with the road construction and concrete foundation construction for the Ash-Dome telescope enclosure. During August 2009, a 0.8m DFM telescope will be installed in the dome; first light with the SUO observatory scheduled for Autumn 2009. In this poster presentation we describe the status of the telescope construction and the possible synergistic in conjunction with SDSS-III for follow-up observations and future instrument development.

CN-strong Stars in the Galactic Halo

Sarah Martell, ARI/ZAH, University of Heidelberg

I present results from a CN bandstrength study of halo red giants in the SEGUE survey. Canonically, halo giants do not exhibit the anticorrelated abundance variations observed among globular cluster stars. However, I find a small fraction of halo giants with CN bandstrength enhancements similar to those observed in similar-metallicity globular cluster giants. Since our understanding of the origin of abundance variations relies on the high density and gas retention ability of clustered star formation, this suggests that the tidal dissolution of globular clusters has played an important, though not dominant, role in the construction of the Galactic stellar halo.

Mira　variables as tracers of the Galactic structure

Noriyuki Matsunaga, University of Tokyo

Distances of Mira variables can be determined based on their period-luminosity relation (PLR) like Cepheids, so that they are good tracers of the Galactic structure. Recently, we have obtained the results of our near-IR survey for variables towards the Galactic Centre (GC) (Matsunaga et al., submitted to MNRAS). We have established a method for the simultaneous estimation of distances and extinctions using the PLRs in JHKs bands. Here we present the results of the GC survey, including the distance to the GC and the structure of the interstellar extinction towards the GC. We also introduce the on-going survey for wider areas of the Galactic bulge and plane. It is expected that Mira variables to be found in the survey reveal the spatial structure of the Galaxy. The kinematic information of these objects would have further impacts on our understanding of the Galaxy.

LasDamas Mock Galaxy Catalogs

Cameron McBride, Vanderbilt University

The statistical strength of galaxy redshift surveys, such as SDSS-I and SDSS-II, have ushered us into the era of precision measurements of galaxy clustering. We are now fitting physical models to measured clustering statistics. Galaxy clustering is thus in a position to directly constrain cosmological and galaxy formation theories. This paradigm shift from qualitative to quantitative demands that we understand the statistical and systematic errors in our measurements. Moreover, we must quantify the theoretical uncertainties in our models, which are no longer clearly sub-dominant to observational errors. We address this emerging need with the LasDamas project (LArge Suite of DArk MAtter Simulations) by producing an unprecedented number of independent and realistic mock galaxy catalogs. To date, we have run over 110 independent N-body realizations using a fixed cosmology and initialized using 2nd order Lagrangian perturbation theory. We populate overdensities of dark matter using the halo occupation distribution framework, designed to match both small and large scale clustering of the observed SDSS data. A series of mock galaxy catalogs matching the geometry of the latest SDSS release (DR7) are created over a wide luminosity range to correspond to Main and LRG volume-limited samples. These galaxy mocks are publicly available

Self-similar Bumps and Wiggles: Isolating the Evolution of the BAO Peak with Power-law Initial Conditions

Chris Orban, Ohio State University

A challenging theoretical neccessity for the next generation of surveys is the ability to precisely model the non-linear gravitational evolution of the baryon acoustic oscillations (BAO) signature in the galaxy distribution. In this study, rather than using standard LambdaCDM initial conditions, we simplify the problem to that of a powerlaw correlation function with a bump. This allows us to use self-similar scaling as a test for numerical artifacts associated with the finite box size or numerical resolution. We isolate the evolution of the BAO bump by running cosmological N-body simulations with these initial conditions, measuring the autocorrelation function, and dividing out the "background" linear-theory powerlaw. We then measure the shift of the BAO peak, and compare the evolution of the bump with the predictions of a variety of methods used in the literature to model the behavior of the BAO signature. Results are presented for both Omega_m = 1.0, Omega_DE = 0.0 (which when coupled with these initial conditions is a universe which evolves with self-similarly) and also for the more realistic case of low Omega_m, Omega_Lambda > 0. Implications for measuring the BAO signature with large-scale structure surveys are discussed.

Testing BOSS target selection for galaxy evolution (Authors: J.Pforr, C. Maraston, D. Thomas)

Janine Pforr, Institute of Cosmology and Gravitation

A robust determination of the stellar masses of galaxies is an imperative requirement for meaningful studies of galaxy formation and evolution, and also for using galaxies as probes for precision cosmology. In particular, high mass galaxies at low redshifts play a crucial role in constraining stellar mass assembly with cosmic time, as recent galaxy formation models imply a conspicuos mass assembly at redshift below 1. The BOSS survey will collect plenty of such data. In this project we study the colour-based target selection criteria for the BOSS survey with respect to the sampled galaxy masses and colours. To investigate this issue, we use SDSS photometry of a representative galaxy sample from the AGES survey. We derive stellar masses using SED fitting and up-to date stellar population models. In a parallel project, we have tested the accuracy of the stellar mass recovery and we prove the efficiency of our technique. We find that the existing selection criteria are well suited in selecting the most massive objects up to z=0.7.

Insights into the Metal Enrichment of the Intergalactic Medium from SDSS QSO Spectra and Constraining BOSS BAO Contamination

Matthew Pieri, Ohio State University

Mechanical feedback is a crucial component of our understanding of galaxy formation and evolution. Metals in the diffuse Intergalactic Medium (IGM) provide a valuable tracer of this feedback and are easiest to observe in the Lyman alpha forest at 2

Constraint on neutrino mass with galaxy power spectrum based on perturbation theory

Shun Saito, The University of Tokyo

We derive cosmological constraint on neutrino mass with SDSS LRG power spectrum measured by Tegmark et al (2006) combining with WMAP5. In contrast with the approach in Tegmark et al (2006) in which nonlinear effect on galaxy power spectrum is empirically modeled, we use standard perturbation theory approach to model the nonlinear effect and compare the results with those in Tegmark et al (2006). This prosiming procedure can be apllied to BOSS, and we also argue the prospects with BOSS.

Measuring galaxy density-velocity power spectrum from redshift surveys

Jiayu Tang, IPMU, University of Tokyo

We propose a model-independent method for measuring density-velocity power spectrum from the measured galaxy distribution in redshift space. Our method is developed by utilizing properties that the redshift-space galaxy distribution has angular modulation depending on the angle between the galaxy position and the line-of-sight direction due to the peculiar velocities. The density-power spectrum is expected to carry additional information on cosmological parameters complementarily to the monopole power spectrum for BAO measurement. Further, the density-velocity spectrum can be used to test gravity theory because the peculiar velocity field is related to the density field via gravity. We test our method using N-body simulations and discuss the feasibility for the proposed BOSS survey.

The Fundamental Plane in DR7

Benjamin Weaver, NYU

We use a sample of galaxies from the SDSS DR7 to derive basic parameters of elliptical galaxies. This sample will be used to fit the fundamental plane of elliptical galaxies. This sample can serve as a starting point to answer questions about techniques for fitting the plane, variations in the fundamental plane with respect to environment and the dependence of elliptical galaxy parameters on the choice of profile model (de Vaucouleurs, Sersic, etc.). We compare the results to parameters derived from previous works & from the NYU Value Added Galaxy Catalog (VAGC).