3,658 research outputs found
Constraints on Assembly Bias from Galaxy Clustering
We constrain the newly-introduced decorated Halo Occupation Distribution
(HOD) model using SDSS DR7 measurements of projected galaxy clustering or
r-band luminosity threshold samples. The decorated HOD is a model for the
galaxy-halo connection that augments the HOD by allowing for the possibility of
galaxy assembly bias: galaxy luminosity may be correlated with dark matter halo
properties besides mass, Mvir. We demonstrate that it is not possible to rule
out galaxy assembly bias using DR7 measurements of galaxy clustering alone.
Moreover, galaxy samples with Mr < -20 and Mr < -20.5 favor strong central
galaxy assembly bias. These samples prefer scenarios in which
high-concentration are more likely to host a central galaxy relative to
low-concentration halos of the same mass. We exclude zero assembly bias with
high significance for these samples. Satellite galaxy assembly bias is
significant for the faintest sample, Mr < -19. We find no evidence for assembly
bias in the Mr < -21 sample. Assembly bias should be accounted for in galaxy
clustering analyses or attempts to exploit galaxy clustering to constrain
cosmology. In addition to presenting the first constraints on HOD models that
accommodate assembly bias, our analysis includes several improvements over
previous analyses of these data. Therefore, our inferences supersede
previously-published results even in the case of a standard HOD analysis.Comment: 15 pages, 8 figures. To be submitted to MNRAS. Comments Welcome.
Python scripts to perform this analysis and MCMC chains will all be made
publicly availabl
Space-Borne Infrared Astronomy
The objective of this grant is to develop the Far IR Photometer (FIRP), one of four focal plane instruments on the IR Telescope in Space (IRTS). The IRTS was successfully launched in March 18, 1995 aboard the Japanese SFU platform. It surveyed the IR sky for approximately 40 days, and was eventually retrieved by NASA's STS. The FIRP succeeded in surveying approximately 5% of the sky in four bands centered at 150, 250, 400 and 700 microns. Several new technologies were developed using the funds from this grant, including: (1) a high performance gas-gap heat-switch, (2) a He-3 sorption refrigerator that is, to date, the only refrigerator to achieve sub-Kelvin temperatures in orbit, (3) high-sensitivity bolometric detectors with NEP less than 10-16 W(Hz(exp l/2)exp 1/2) when operated from a 300 mK heat sink, (4) readout electronics capable of providing DC stability for the bolometric detectors. Excess noise of unknown origin significantly reduced the sensitivity of the FIRP on orbit. Nevertheless, scientifically significant observations of the spectrum and temperature of the interstellar dust were made, and have been reported
Brightest galaxies as halo centre tracers in SDSS DR7
Determining the positions of halo centres in large-scale structure surveys is
crucial for many cosmological studies. A common assumption is that halo centres
correspond to the location of their brightest member galaxies. In this paper,
we study the dynamics of brightest galaxies with respect to other halo members
in the Sloan Digital Sky Survey DR7. Specifically, we look at the line-of-sight
velocity and spatial offsets between brightest galaxies and their neighbours.
We compare those to detailed mock catalogues, constructed from high-resolution,
dark-matter-only -body simulations, in which it is assumed that satellite
galaxies trace dark matter subhaloes. This allows us to place constraints on
the fraction of haloes in which the brightest galaxy is not the
central. Compared to previous studies we explicitly take into account the
unrelaxed state of the host haloes, velocity offsets of halo cores and
correlations between and the satellite occupation. We find that
strongly decreases with the luminosity of the brightest galaxy
and increases with the mass of the host halo. Overall, in the halo mass range
we find , in good
agreement with a previous study by Skibba et al. We discuss the implications of
these findings for studies inferring the galaxy--halo connection from satellite
kinematics, models of the conditional luminosity function and galaxy formation
in general.Comment: 24 pages, 15 figures. Accepted for publication in MNRA
What\u27ll We Do With Him Boys? : The Yanks Made A Monkey Out Of You
https://digitalcommons.library.umaine.edu/mmb-vp/2656/thumbnail.jp
Charitable Memberships, Volunteering, and Discounts: Evidence from a Large-Scale Online Field Experiment
Despite the increasing use by charities, significant uncertainty exists about optimal online fundraising mechanisms, especially when large donor pools show substantial heterogeneities. We use an online natural field experiment with over 700,000 subjects to test theory on price discounts and show large differences in donation behavior between donors who have previously given money and/or volunteered. For example, framing the charity's membership price as a discount increases response rates and decreases conditional contributions from former volunteers, but not from past money donors. Our study thereby demonstrates the importance of conditioning fundraising strategies on the specifics of past donation dimensions.
Maturing Satellite Kinematics into a Competitive Probe of the Galaxy-Halo Connection
The kinematics of satellite galaxies moving in a dark matter halo are a
direct probe of the underlying gravitational potential. Thus, the phase-space
distributions of satellites represent a powerful tool to determine the
galaxy-halo connection from observations. By stacking the signal of a large
number of satellite galaxies this potential can be unlocked even for haloes
hosting a few satellites on average. In this work, we test the impact of
various modelling assumptions on constraints derived from analysing satellite
phase-space distributions in the non-linear, 1-halo regime. We discuss their
potential to explain the discrepancy between average halo masses derived from
satellite kinematics and gravitational lensing previously reported.
Furthermore, we develop an updated, more robust analysis to extract constraints
on the galaxy-halo relation from satellite properties in spectroscopic galaxy
surveys such as the SDSS. We test the accuracy of this approach using a large
number of realistic mock catalogues. Furthermore, we find that constraints
derived from such an analysis are complementary and competitive with respect to
the commonly used galaxy clustering and galaxy-galaxy lensing observables.Comment: 24 pages, 15 figures; resubmitted to MNRAS after first referee repor
Updated Results on the Galaxy-Halo Connection from Satellite Kinematics in SDSS
We present new results on the relationship between central galaxies and dark
matter haloes inferred from observations of satellite kinematics in the Sloan
Digital Sky Survey (SDSS) DR7. We employ an updated analysis framework that
includes detailed mock catalogues to model observational effects in SDSS. Our
results constrain the colour-dependent conditional luminosity function (CLF) of
dark matter haloes, as well as the radial profile of satellite galaxies.
Confirming previous results, we find that red central galaxies live in more
massive haloes than blue galaxies at fixed luminosity. Additionally, our
results suggest that satellite galaxies have a radial profile less centrally
concentrated than dark matter but not as cored as resolved subhaloes in dark
matter-only simulations. Compared to previous works using satellite kinematics
by More et al., we find much more competitive constraints on the galaxy-halo
connection, on par with those derived from a combination of galaxy clustering
and galaxy-galaxy lensing. We compare our results on the galaxy-halo connection
to other studies using galaxy clustering and group catalogues, showing very
good agreement between these different techniques. We discuss future
applications of satellite kinematics in the context of constraining cosmology
and the relationship between galaxies and dark matter haloes.Comment: 18 pages, 10 figures, submitted to MNRAS, comments welcom
So Long Sal : The Best Of Friends Must Part
https://digitalcommons.library.umaine.edu/mmb-vp/5422/thumbnail.jp
SAMBA: Superconducting antenna-coupled, multi-frequency, bolometric array
We present a design for a multipixel, multiband (100 GHz, 200 GHz and 400 GHz) submillimeter instrument: SAMBA (Superconducting Antenna-coupled, Multi-frequency, Bolometric Array). SAMBA uses slot antenna coupled bolometers and microstrip filters. The concept allows for a much more compact, multiband imager compared to a comparable feedhorn-coupled bolometric system. SAMBA incorporates an array of slot antennas, superconducting transmission lines, a wide band multiplexer and superconducting transition edge bolometers. The transition-edge film measures the millimeter-wave power deposited in the resistor that terminates the transmission line
A Mother\u27s Prayer For Her Boy Out There
https://digitalcommons.library.umaine.edu/mmb-vp/4924/thumbnail.jp
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