2752138
A pilot survey of H I in field galaxies at redshift z ~ 0.2
We present the first results of a targeted survey carried out with the 305 m Arecibo telescope to detect H I line emission from galaxies at redshift z > 0.16. The targets, selected from the Sloan Digital Sky Survey database, are noninteracting disk galaxies in relatively isolated fields. We present here the H I spectra and derived H I parameters for 10 objects detected in this pilot program. All are massive disk galaxies in the redshift interval 0.17-0.25 (i.e., 2-3 Gyr look-back time), with H I masses MH I = (3-8) × 1010 M☉ and high gas mass fractions (H I-to-stellar mass ratios ~ 10%-30%). Our results demonstrate the efficacy of exploiting Arecibo's large collecting area to measure the H I mass and rotational velocity of galaxies above redshift z = 0.2. In particular, this sample includes the highest redshift detections of H I emission from individual galaxies made to date. Extension of this pilot program will allow us to study the H I properties of field galaxies at cosmological distances, thus complementing ongoing radio synthesis observations of cluster samples at z ~ 0.2.
16921302
Toward a resolution of the discrepancy between different estimators of star formation rate
Different wavelength regimes and methods for estimating the space density of the star formation rate (SFR) result in discrepant values. While it is recognized that ultraviolet (UV) and Hα emission-line data must be corrected for the effects of extinction, the magnitude of the required correction is uncertain. Even when these corrections are made there remains a significant discrepancy between SFRs derived from UV and Hα measurements compared with those derived from far-infrared (FIR) and radio luminosities. Since the FIR-radio–derived SFRs are not affected by extinction and simple corrections to reconcile the UV and Hα measurement with these do not fully account for the discrepancies, a more sophisticated correction may be required. Recent results suggest that at least part of the solution may be a form of extinction that increases with increasing SFR (or luminosity, given the common assumption that SFR is proportional to luminosity). We present an analysis of the effects of a dust reddening dependent on star formation rate applied to estimators of SFR. We show (1) that the discrepancies between Hα and FIR-radio SFR estimates may be explained by such an effect and we present an iterative method for applying the correction and (2) that UV-based estimates of SFR are harder to reconcile with FIR-radio estimates using this method, although the extent of the remaining discrepancy is less than for a non-SFR–dependent correction. Particularly at high redshift, our understanding of extinction at UV wavelengths may require a still more complex explanation.
119191264
Classification of Stellar Spectra with LLE
We investigate the use of dimensionality reduction techniques for the classification of stellar spectra selected from the SDSS. Using local linear embedding (LLE), a technique that preserves the local (and possibly non-linear) structure within high dimensional data sets, we show that the majority of stellar spectra can be represented as a one dimensional sequence within a three dimensional space. The position along this sequence is highly correlated with spectral temperature. Deviations from this “stellar locus” are indicative of spectra with strong emission lines (including misclassified galaxies) or broad absorption lines (e.g. Carbon stars). Based on this analysis, we propose a hierarchical classification scheme using LLE that progressively identifies and classifies stellar spectra in a manner that requires no feature extraction and that can reproduce the classic MK classifications to an accuracy of one type.
118985428
Three-Point Correlation Functions of SDSS Galaxies in Redshift Space: Morphology, Color, and Luminosity Dependence
We present measurements of the redshift-space three-point correlation function of galaxies in the Sloan Digital Sky Survey (SDSS). For the first time, we analyze the dependence of this statistic on galaxy morphology, color, and luminosity. In order to control systematics due to selection effects, we used r-band, volume-limited samples of galaxies, constructed from magnitude-limited SDSS data (14.5 <r< 17.5), and further divided the samples into two morphological types (early and late) or two color populations (red and blue). The three-point correlation function of SDSS galaxies follows the hierarchical relation well, and the reduced three-point amplitudes in redshift-space are almost scale-independent (Qz =0 .5 ∼ 1.0). In addition, their dependence on the morphology, color, and luminosity is not statistically significant. Given the robust morphological, color, and luminosity dependences of the two-point correlation function, this implies that galaxy biasing is complex on weakly non-linear to non-linear scales. We show that a simple deterministic linear relation with the underlying mass could not explain our measurements on these scales.
119214510
INTERPOLATING MASKED WEAK-LENSING SIGNAL WITH KARHUNEN-LOÈVE ANALYSIS
We explore the utility of Karhunen-Lo?ve (KL) analysis in solving practical problems in the analysis of gravitational shear surveys. Shear catalogs from large-field weak-lensing surveys will be subject to many systematic limitations, notably incomplete coverage and pixel-level masking due to foreground sources. We develop a method to use two-dimensional KL eigenmodes of shear to interpolate noisy shear measurements across masked regions. We explore the results of this method with simulated shear catalogs, using statistics of high-convergence regions in the resulting map. We find that the KL procedure not only minimizes the bias due to masked regions in the field, it also reduces spurious peak counts from shape noise by a factor of ~3 in the cosmologically sensitive regime. This indicates that KL reconstructions of masked shear are not only useful for creating robust convergence maps from masked shear catalogs, but also offer promise of improved parameter constraints within studies of shear peak statistics.
8278022
First Results from the SPICES Survey
We present first results from SPICES, the Spectroscopic, Photometric, Infrared-Chosen Extragalactic Survey. SPICES is comprised of four ~30 square arcminute high Galactic latitude fields with deep BRIzJK imaging reaching depths of ~25th magnitude (AB) in the optical and ~23rd magnitude (AB) in the near-infrared. To date we have 626 spectroscopic redshifts for infrared-selected SPICES sources with K 1. One of the SPICES fields has been the target of a deep 190 ksec Chandra exposure; we discuss initial results from analysis of that data set. Finally, we briefly discuss a successful campaign to identify high-redshift sources in the SPICES fields.
118417697
First constraints on the ultra-high energy neutrino flux from a prototype station of the Askaryan Radio Array
Abstract The Askaryan Radio Array (ARA) is an ultra-high energy ( > 10 17  eV) cosmic neutrino detector in phased construction near the south pole. ARA searches for radio Cherenkov emission from particle cascades induced by neutrino interactions in the ice using radio frequency antennas ( ∼ 150 - 800  MHz) deployed at a design depth of 200 m in the Antarctic ice. A prototype ARA Testbed station was deployed at ∼ 30  m depth in the 2010–2011 season and the first three full ARA stations were deployed in the 2011–2012 and 2012–2013 seasons. We present the first neutrino search with ARA using data taken in 2011 and 2012 with the ARA Testbed and the resulting constraints on the neutrino flux from 10 17 - 10 21  eV.
31976951
Observation of ultrahigh-energy cosmic rays with the ANITA balloon-borne radio interferometer.
We report the observation of 16 cosmic ray events with a mean energy of 1.5 × 10¹⁹ eV via radio pulses originating from the interaction of the cosmic ray air shower with the Antarctic geomagnetic field, a process known as geosynchrotron emission. We present measurements in the 300-900 MHz range, which are the first self-triggered, first ultrawide band, first far-field, and the highest energy sample of cosmic ray events collected with the radio technique. Their properties are inconsistent with current ground-based geosynchrotron models. The emission is 100% polarized in the plane perpendicular to the projected geomagnetic field. Fourteen events are seen to have a phase inversion due to reflection of the radio beam off the ice surface, and two additional events are seen directly from above the horizon. Based on a likelihood analysis, we estimate angular pointing precision of order 2° for the event arrival directions.
35667083
Status of ANITA and ANITA-lite
We describe a new experiment to search for neutrinos with energies above 3 × 1018 eV based on the observation of short duration radio pulses that are emitted from neutrino-initiated cascades. The primary objective of the ANtarctic Impulse Transient Antenna (ANITA) mission is to measure the flux of Greisen-Zatsepin-Kuzmin (GZK) neutrinos and search for neutrinos from Active Galactic Nuclei (AGN). We present first results obtained from the successful launch of a 2-antenna prototype instrument (called ANITA-lite) that circled Antarctica for 18 days during the 03/04 Antarctic campaign and show preliminary results from attenuation length studies of electromagnetic waves at radio frequencies in Antarctic ice. The ANITA detector is funded by NASA, and the first flight is scheduled for December 2006.
126012638
Studies of hadron-electron separators for the ZEUS barrel calorimeter
Abstract Two possible upgrades, a shower maximum detector and a presampler, designed to improve the low energy electron/hadron separation capabilities of the ZEUS barrel calorimeter are described and test-beam results are reported. The presampler can also be used to correct for energy loss of particles traversing the dead material in front of the calorimeter.
120506645
Results from the ANITA experiment (Analysis A)
The ANITA (ANtarctic Impulsive Transient Antenna) is a balloon-borne neutrino telescope which consists of an array of 32 broadband horn antennas. It successfully completed a 35 day flight over Antarctica during the 2006-2007 austral summer. The primary goal of ANITA is to search for astrophysical neutrinos with energies E > 1019 eV by detecting radio Cherenkov signals from neutrino-induced showers in the Antarctic ice. There are two independent data analysis groups in the ANITA experiment based on data blinding and analysis methods. We present results from one of the analysis groups with an event blinding approach.