arXiv subjects

S. Schneider

Publications and source records attributed to S. Schneider.

At least 37 records · Page 2Linked to original sources

arXiv2010

The Arecibo Galaxy Environment Survey III: Observations Toward the Galaxy Pair NGC 7332/7339 and the Isolated Galaxy NGC 1156

Two 5 square degree regions around the NGC 7332/9 galaxy pair and the isolated galaxy NGC 1156 have been mapped in the 21-cm line of neutral hydrogen (HI) with the Arecibo L-band Feed Array out to a redshift of ~0.065$ (~20,000$ km/s) as part of the Arecibo Galaxy Environment Survey. One of the aims of this survey is to investigate the environment of galaxies by identifying dwarf companions and interaction remnants; both of these areas provide the potential for such discoveries. The neutral hydrogen observations were complemented by optical and radio follow-up observations with a number of telescopes. A total of 87 galaxies were found, of which 39 (45 per cent) were previously cataloged and 15 (17 per cent) have prior redshifts. Two dwarf galaxies have been discovered in the NGC 7332 group and a single dwarf galaxy in the vicinity NGC 1156 . A parallel optical search of the area revealed one further possible dwarf galaxy near NGC 7332.

astro-ph.CO↗

arXiv2010

The Arecibo L-band Feed Array Zone of Avoidance Survey I: Precursor Observations through the Inner and Outer Galaxy

The Arecibo L-band Feed Array (ALFA) is being used to conduct a low-Galactic latitude survey, to map the distribution of galaxies and large-scale structures behind the Milky Way through detection of galaxies' neutral hydrogen (HI) 21-cm emission. This Zone of Avoidance (ZOA) survey finds new HI galaxies which lie hidden behind the Milky Way, and also provides redshifts for partially-obscured galaxies known at other wavelengths. Before the commencement of the full survey, two low-latitude precursor regions were observed, totalling 138 square degrees, with 72 HI galaxies detected. Detections through the inner Galaxy generally have no cataloged counterparts in any other waveband, due to the heavy extinction and stellar confusion. Detections through the outer Galaxy are more likely to have 2MASS counterparts. We present the results of these precursor observations, including a catalog of the detected galaxies, with their HI parameters. The survey sensitivity is well described by a flux- and linewidth-dependent signal-to-noise ratio of 6.5. ALFA ZOA galaxies which also have HI measurements in the literature show good agreement between our measurements and previous work. The inner Galaxy precursor region was chosen to overlap the HI Parkes Zone of Avoidance Survey so ALFA performance could be quickly assessed. The outer Galaxy precursor region lies north of the Parkes sky. Low-latitude large-scale structure in this region is revealed, including an overdensity of galaxies near l = 183 deg and between 5000 - 6000 km/s in the ZOA. The full ALFA ZOA survey will be conducted in two phases: a shallow survey using the observing techniques of the precursor observations, and also a deep phase with much longer integration time, with thousands of galaxies predicted for the final catalog.

astro-ph.CO↗

arXiv2009

A Search for Dust Emission in the Leo Intergalactic Cloud

We present a search for infrared dust emission associated with the Leo cloud, a large intergalactic cloud in the M96 group. Mid-infrared and far-infrared images were obtained with IRAC and MIPS on the Spitzer Space Telescope. Our analysis of these maps is done at each wavelength relative to the HI spatial distribution. We observe a probable detection at 8 microns and a marginal detection at 24 microns associated with the highest HI column densities in the cloud. At 70 and 160 microns, upper limits on the dust emission are deduced. The level of the detection is low so that the possibility of a fortuitous cirrus clump or of an overdensity of extragalactic sources along the line of sight can not be excluded. If this detection is confirmed, the quantities of dust inferred imply a dust to gas ratio in the intergalactic cloud up to a few times solar but no less than 1/20 solar. A confirmed detection would therefore exclude the possibility that the intergalactic cloud has a primordial origin. Instead, this large intergalactic cloud could therefore have been formed through interactions between galaxies in the group.

astro-ph.CO↗

arXiv2007

NIBLES: an HI census of local SDSS galaxies

NIBLES is a Key Project proposed for the 100m-class Nancay Radio Telescope (NRT) in France. Its aim is a census of the HI gas content and dynamics of 4,000 Sloan Digital Sky Survey galaxies in the Local Volume (900<cz<12,000 km/s). The galaxies were selected based on their total stellar mass (absolute z-band magnitude Mz), and are distributed evenly over the entire range of Mz covered by local SDSS galaxies (-10 to -24 mag, for H0=70 km/s/Mpc). A pilot survey is being made of over 600 galaxies. NIBLES will be complementary to the ALFALFA and EBHIS blind HI surveys, which will detect a different ensemble of local galaxies, and which our pilot survey results indicate will detect about 40-45% of the NIBLES sample. NIBLES is an open collaboration and anyone interested in the science and willing to contribute to the project is welcome to join the score of NIBLErS.

astro-ph↗

arXiv2007

The Arecibo Galaxy Environment Survey: II. A HI view of the Abell cluster 1367 and its outskirts

We present 21 cm HI line observations of 5x1 square degrees centered on the local Abell cluster 1367 obtained as part of the Arecibo Galaxy Environment Survey. One hundred sources are detected (79 new HI measurements and 50 new redshifts), more than half belonging to the cluster core and its infalling region. Combining the HI data with SDSS optical imaging we show that our HI selected sample follows scaling relations similar to the ones usually observed in optically selected samples. Interestingly all galaxies in our sample appear to have nearly the same baryon fraction independently of their size, surface brightness and luminosity. The most striking difference between HI and optically selected samples resides in their large scale distribution: whereas optical and X-ray observations trace the cluster core very well, in HI there is almost no evidence of the presence of the cluster. Some implications on the determination of the cluster luminosity function and HI distribution for samples selected at different wavelength are also discussed.

astro-ph↗

arXiv2007

The ALFA Zone of Avoidance Survey: Results from the Precursor Observations

The Arecibo L-band Feed Array Zone of Avoidance Survey (ALFA ZOA) will map 1350-1800 square degrees at low Galactic latitude, providing HI spectra for galaxies in regions of the sky where our knowledge of local large scale structure remains incomplete, owing to obscuration from dust and high stellar confusion near the Galactic plane. Because of these effects, a substantial fraction of the galaxies detected in the survey will have no optical or infrared counterparts. However, near infrared follow up observations of ALFA ZOA sources found in regions of lowest obscuration could reveal whether some of these sources could be objects in which little or no star formation has taken place ("dark galaxies"). We present here the results of ALFA ZOA precursor observations on two patches of sky totaling 140 square degrees (near l=40 degrees, and l=192 degrees). We have measured HI parameters for detections from these observations, and cross-correlated with the NASA/IPAC Extragalactic Database (NED). A significant fraction of the objects have never been detected at any wavelength. For those galaxies that have been previously detected, a significant fraction have no previously known redshift, and no previous HI detection.

astro-ph↗

arXiv2006

The Arecibo Galaxy Environment Survey: Precursor Observations of the NGC 628 group

The Arecibo Galaxy Environment Survey (AGES) is one of several HI surveys utilising the new Arecibo L-band Feed Array (ALFA) fitted to the 305m radio telescope at Arecibo. The survey is specifically designed to investigate various galactic environments to higher sensitivity, higher velocity resolution and higher spatial resolution than previous fully sampled, 21 cm multibeam surveys. The emphasis is on making detailed observations of nearby objects although the large system bandwidth (100 MHz) will allow us to quantify the HI properties over a large instantaneous velocity range. In this paper we describe the survey and its goals and present the results from the precursor observations of a 5 degree x 1 degree region containing the nearby (~10 Mpc) NGC 628 group. We have detected all the group galaxies in the region including the low mass (M{HI}~10^7Mo) dwarf, dw0137+1541 (Briggs, 1986). The fluxes and velocities for these galaxies compare well with previously published data. There is no intra-group neutral gas detected down to a limiting column density of 2x10^{18}cm^{-2}. In addition to the group galaxies we have detected 22 galaxies beyond the NGC 628 group, 9 of which are previously uncatalogued.(Abridged)

astro-ph↗

arXiv2006

The reaction pi N to pi pi N in a meson-exchange approach

A resonance model for two-pion production in the pion-nucleon reaction is developed that includes information obtained in the analysis of pion-nucleon scattering in a meson-exchange model. The baryonic resonances Delta(1232), N*(1440), N*(1520), N*(1535), and N*(1650) are included. The model reproduces the total cross sections up to kinetic energies of the incident pion of 350 MeV and obtains the shapes of the differential cross sections in reasonable agreement with the data.

nucl-th↗

arXiv2003

Diagnosis, prescription and prognosis of a Bell-state filter by quantum process tomography

Using a Hong-Ou-Mandel interferometer, we apply the techniques of quantum process tomography to characterize errors and decoherence in a prototypical two-photon operation, a singlet-state filter. The quantum process tomography results indicate a large asymmetry in the process and also the required operation to correct for this asymmetry. Finally, we quantify errors and decoherence of the filtering operation after this modification.

quant-ph↗

arXiv2002

Bose-Einstein Condensation in a simple Microtrap

A Bose-Einstein condensate is created in a simple and robust miniature Ioffe-Pritchard trap, the so-called Z trap. This trap follows from the mere combination of a Z-shaped current carrying wire and a homogeneous bias field. The experimental procedure allows condensation of typically 3x10^5 Rb-87 atoms in the |F=2, m_F=2> state close to any mirroring surface, irrespective of its structure, thus it is ideally suited as a source for cold atom physics near surfaces.

cond-mat.soft↗

arXiv2002

Positive pion absorption on 3He using modern trinucleon wave functions

We study pion absorption on 3He employing trinucleon wave functions calculated from modern realistic NN interactions (Paris, CD Bonn). Even though the use of the new wave functions leads to a significant improvement over older calculations with regard to both cross section and polarization data, there are hints that polarization data with quasifree kinematics cannot be described by just two-nucleon absorption mechanisms.

nucl-th↗

arXiv2002

Photoproduction of the Eta Meson from the Deuteron Near Threshold

Very recent data for the reaction gamma{d} --> eta{np} are analyzed within a model that includes contributions from the impulse approximation and next order corrections due to the np and eta{N} interactions in the final state. Comparison between the calculations and data indicate sizable contributions from the np and eta{N} final state interactions close to threshold.

nucl-th↗

arXiv2002

Incoherent Eta Photoproduction from the Deuteron near Threshold

Very recent data for the reaction gamma+d ->eta np, namely total cross sections, angular and momentum spectra, are analyzed within a model that includes contributions from the impulse approximation and next order corrections due to the np and eta-N interactions in the final state. Comparison between the calculations and the new data indicate sizable contributions from the np and eta-N final state interactions. Some systematic discrepancies between the calculations and the data are also found.

nucl-th↗

arXiv2002

Multipartite Classical and Quantum Secrecy Monotones

In order to study multipartite quantum cryptography, we introduce quantities which vanish on product probability distributions, and which can only decrease if the parties carry out local operations or carry out public classical communication. These ``secrecy monotones'' therefore measure how much secret correlations are shared by the parties. In the bipartite case we show that the mutual information is a secrecy monotone. In the multipartite case we describe two different generalisations of the mutual information, both of which are secrecy monotones. The existence of two distinct secrecy monotones allows us to show that in multipartite quantum cryptography the parties must make irreversible choices about which multipartite correlations they want to obtain. Secrecy monotones can be extended to the quantum domain and are then defined on density matrices. We illustrate this generalisation by considering tri-partite quantum cryptography based on the Greenberger-Horne-Zeilinger (GHZ) state. We show that before carrying out measurements on the state, the parties must make an irreversible decision about what probability distribution they want to obtain.

quant-ph↗

arXiv2001

Entanglement in the Dicke model

We show how an ion trap, configured for the coherent manipulation of external and internal quantum states, can be used to simulate the irreversible dynamics of a collective angular momentum model known as the Dicke model. In the special case of two ions, we show that entanglement is created in the coherently driven steady state with linear driving. For the case of more than two ions we calculate the entanglement between two ions in the steady state of the Dicke model by tracing over all the other ions. The entanglement in the steady state is a maximum for the parameter values corresponding roughly to a bifurcation of a fixed point in the corresponding semiclassical dynamics. We conjecture that this is a general mechanism for entanglement creation in driven dissipative quantum systems.

quant-ph↗

arXiv2001

Eta-N Final State Interaction in incoherent Photoproduction of Eta-mesons from the Deuteron near Threshold

An analysis of incoherent photoproduction of $η$ mesons off the deuteron for photon energies from threshold to 800 MeV is presented. The dominant contribution, the $γ$N-$η$N amplitude, is described within an isobar model. Effects of the final state interactions in the $NN$ as well as the $ηN$ systems are included employing models derived within the meson-exchange approach. It is found that their consideration is important. Specifically, due to an interference effect the influence of the $ηN$ final state interaction is enhanced in the reaction $γd \to np η$ close to threshold.

nucl-th↗

arXiv2000

2MASS Extended Sources in the Zone of Avoidance

The Two Micron All Sky Survey (2MASS) is now underway and will provide a complete census of galaxies as faint as 13.5 mag (3 mJy) at 2.2 microns for most of the sky, and ~12.1 mag (10 mJy) for regions veiled by the Milky Way. This census has already discovered nearby galaxies previously hidden behind our Galaxy, and will allow delineation of large-scale structures in the distribution of galaxies across the whole sky. Here we report the detection and discovery of new extended sources from this survey for fields incorporating the Galactic plane at longitudes between 40 and 70 deg. The area-normalized detection rate is ~1-2 galaxies per deg^2 brighter than 12.1 mag (10 mJy), roughly constant with Galactic latitude throughout the "Zone of Avoidance", of which 85-95% are newly discovered sources. In conjunction with the deep HI surveys, 2MASS will greatly increase the current census of galaxies hidden behind the Milky Way.

astro-ph↗

arXiv2000

2MASS Extended Source Catalog: Overview and Algorithms

The 2 Micron All-Sky Survey (2MASS) will observe over one-million galaxies and extended Galactic sources covering the entire sky at wavelengths between 1 and 2 microns. The survey catalog will have both high completeness and reliability down to J = 15.0 and Ks = 13.5 mag, equivalent to 1.6 mJy and 2.9 mJy, respectively. This paper describes the basic algorithms used to detect and characterize extended sources in the 2MASS database and catalog. Critical procedures include tracking the point spread function, image background removal, artifact removal, photometry and basic parameterization, star-galaxy discrimination and object classification using a decision tree technique. Examples of extended sources encountered in 2MASS are given.

astro-ph↗