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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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NASA NTRS2000

X-Ray Companion Sources to Seyfert 2 Galaxies

The ROSAT observations supported by this grant provided improved positions for the "companion sources" to 3 Seyfert 2 galaxies, as proposed. Follow-up observations at the MMT and CTIO found that the optical counterparts to these sources were a mixture of normal stars (mainly M dwarfs) and background AGN. This surprising result suggests that the reported excess of PSPC sources around Seyfert 2 galaxies was a statistical fluctuation, and does not indicate a new population of bright non-nuclear X-ray sources in these objects. The report of Xia et al., that a companion to MRK273 was a dwarf galaxy at the same redshift containing another Seyfert 2 galaxy was withdrawn in an erratum. (The true redshift of the companion was much larger than that of MRK273.) For the time being then this question is closed. A re-examination of the "companions" using Chandra data will become possible in the next year. If the optical 'counterparts' we found are not the true counterparts, or if the counterparts we found were the background of inevitable interlopers ('serendipitous') sources, there may remain a high X-ray luminosity population associated with Seyfert 2 galaxies.

Elvis, Martin↗
NASA NTRS1993

H I 21 centimeter observations and I-band CCD surface photometry of spiral galaxies behind the Virgo Cluster and toward its antipode

Sample selection, radio and optical data acquisition and reduction, and observation results are presented for spiral galaxies behind the Virgo Cluster and toward its antipode. I-band CCD photometry was obtained for all the bright galaxies and part of the sample of faint galaxies in the two local volumes was studied. The statistical properties of the galaxy samples are discussed.

Lu, N. Y.↗
NASA NTRS1983

First-ranked galaxies in groups

A statistical analysis of five group catalogs shows that the B(0) magnitudes of first-ranked group members are consistent with a statistical model in which the luminosities of all group members are drawn from the same distribution. As in the Hickson compact groups, indications are that first-ranked group members are only rarely the products of distinctive evolutionary processes. Distance-dependent selection effects can introduce spurious correlations among group parameters which may appear to support environment-dependent evolution of the first-ranked group members.

Geller, M. J.↗
DOE OSTI2022

The edge-on Galaxies in the Pan-STARRS survey (EGIPS)

ABSTRACT We present a catalogue of 16 551 edge-on galaxies created using the public DR2 data of the Pan-STARRS survey. The catalogue covers the three quarters of the sky above Dec. = −30°. The galaxies were selected using a convolutional neural network, trained on a sample of edge-on galaxies identified earlier in the SDSS survey. This approach allows us to dramatically improve the quality of the candidate selection and perform a thorough visual inspection in a reasonable amount of time. The catalogue provides homogeneous information on astrometry, SExtractor photometry, and non-parametric morphological statistics of the galaxies. The photometry is reliably for objects in the 13.8–17.4 r-band magnitude range. According to the HyperLeda data base, redshifts are known for about 63 per cent of the galaxies in the catalogue. Our sample is well separated into the red sequence and blue cloud galaxy populations. The edge-on galaxies of the red sequence are systematically Δ(g − i) ≈ 0.1 mag redder than galaxies oriented at an arbitrary angle to the observer. We found a variation of the galaxy thickness with the galaxy colour. The red sequence galaxies are thicker than the galaxies of the blue cloud. In the blue cloud, on average, thinner galaxies turn out to be bluer. In the future, based on this catalogue it is intended to explore the three-dimensional structure of galaxies of different morphologies, as well as to study the scaling relations for discs and bulges.

Makarov, D. (ORCID:0000000191103221)↗
NASA NTRS2003

Evolution of Galaxies and the Star Formation Rate in the Infrared

A central goal of extragalactic observational astronomy is to understand how normal galaxies evolve with redshift, and particularly when galaxies formed their stars. While optical and rest-frame UV observations have begun to address these issues, the interpretation of such data is particularly challenging because of the sensitivity to dust obscuration (at optical and UV wavelengths). The absorbed light is re-radiated at IR wavelengths, hence the optimal indicators of the star formation rate (SFR) is at a rest-frame wavelength of approx. 60 microns. The SIRTF mission will revolutionize the study of the global evolution of the SFR by providing mass-selected, complete samples of galaxies and far-IR estimators of the SFR. SIRTF will be two orders of magnitude more sensitive than previous IR space missions, and therefore will open up a completely new region of parameter space in sensitivity and angular resolution. This research program will study the SFR using statistical samples of galaxies in the local universe, at intermediate redshifts, and set the stage for continuing studies up to z = 5. The overall research program is divided into three main investigations: a Mid-IR Hubble Atlas and SFR estimators in the local universe, evolution of the SFR at 0 less than z less that 1 using pencil beam redshift surveys, and Galaxy formation and evolution at 1 less than z less than 5.

Pahre, Michael A.↗
NASA NTRS2000

Detection of X-ray Emission From Galaxies Inside The Bootes Void

We report the x-ray properties of Bootes void galaxies detected by the ROSAT All-Sky Survey (RASS). By searching the fields of 26 radio and 27 emission-line-selected void galaxies, we have detected 9 x-ray emitting void galaxies at >2.7-sigma confidence level. Five of these 9 galaxies are in the IP,AS subsample. We expect 2 detections at the redshift of the Bootes void based on previous positional cross-correlation studies of the RASS and IRAS Point Source Catalogue sources. Three of the x-ray emitting galaxies are AGNs (IRAS~14288+5255, Mrk~845, and IRAS 15195+5050), and the remaining 6 are all likely emission line galaxies (PC~1357+4641, CG~547, CG~922, IRAS~14SOO+4804, CG~637, and IRAS~15092+3940). The far infrared flux levels of the AGN sources implies most of the observed x-ray emissivity is from starburst activity. We have carried out timing and spectral analysis for the narrow-line Seyfert 1 galaxy Mrk~845. Poor statistics prevents detailed analysis of the remaining sources. only two galaxies in our sample, BHI 1514+3819 and FSS 1515+3823, were observed during ROSAT pointed observations resulting in a nondetection at the 1-sigma level.

Kim, Chulhee↗
NASA NTRS2001

Detection of X-Ray Emission from Galaxies Inside the Bootes Void

We report the X-ray properties of Bootes void galaxies detected by the ROSAT All-Sky Survey (RASS). By searching the fields of 26 radio and 27 emission-line-selected void galaxies, we have detected nine X-ray-emitting void galaxies at greater than 2.7 sigma confidence level. Five of these nine galaxies are in the IRAS subsample. Two of the IRAS galaxies were previously identified in positional cross-correlation studies of the RASS and IRAS Point Source Catalogue sources. Three of the X-ray-emitting galaxies are active galactic nuclei (AGNs; IRAS 14288+5255, Mrk 845, and IRAS 15195+5050), three are emission-line galaxies (PC 1357+4641, CG 547, and CG 922), and the remaining three are of unknown spectral type (IRAS 14500+4804, CG 637, and MAS 15092+3940). The far-infrared flux levels of the AGN sources imply that most of the observed X-ray emissivity is from starburst activity. We have carried out timing and spectral analysis for the Seyfert 1 galaxy Mrk 845. Poor statistics prevents detailed analysis of the remaining sources. Only two galaxies in our sample, BHI 1514+3819 and FSS 1515+3823, were observed during ROSAT pointed observations resulting in a nondetection at the 1 sigma level.

Kim, Chulhee↗
NASA NTRS1992

Using arcs in clusters of galaxies as probes to cluster potentials and the faint blue galaxies

An extensive study of the statistical properties of highly magnified gravitational images of background galaxies produced by clusters of galaxies (generally known as arcs) is undertaken. After summarizing the results obtained from present observations (described in detail elsewhere), techniques are described for observations to improve upon these results, and to obtain further information on the potentials of the lensing clusters and the faint blue galaxies acting as sources. The most important information that can be obtained from the arcs is, with respect to the clusters, on the total density profile and the substructure at the small scales probed by the arcs, and, with respect to the background sources, on their angular sizes and redshifts.

Miralda-Escude, Jordi↗
DOE OSTI2025

Galaxy Clustering with LSST: Effects of Number Count Bias from Blending

The Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST) will survey the southern sky to create the largest galaxy catalog to date, and its statistical power demands an improved understanding of systematic effects such as source overlaps, also known as blending. In this work we study how blending introduces a bias in the number counts of galaxies (instead of the flux and colors), and how it propagates into galaxy clustering statistics. We use the 300 deg 2 DC2 image simulation and its resulting galaxy catalog (LSST Dark Energy Science Collaboration et al. 2021) to carry out this study. We find that, for a LSST Year 1 (Y1)-like cosmological analyses, the number count bias due to blending leads to small but statistically significant differences in mean redshift measurements when comparing an observed sample to an unblended calibration sample. In the two-point correlation function, blending causes differences greater than 3σ on scales below approximately 10', but large scales are unaffected. We fit Ω m and linear galaxy bias in a Bayesian cosmological analysis and find that the recovered parameters from this limited area sample, with the LSST Y1 scale cuts, are largely unaffected by blending. Our main results hold when considering photometric redshift and a LSST Year 5 (Y5)-like sample.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1986

Narrow-angle tail radio sources and evidence for radial orbits in Abell clusters

Published observational data on the tail orientations (TOs) of 60 narrow-angle-tail (NAT) radio sources in Abell clusters of galaxies are analyzed statistically using a maximum-likelihood approach. The results are presented in a table, and it is found that the observed TO distributions in the whole sample and in subsamples of morphologically regular NATs and NATs with pericentric distances d greater than 500 kpc are consistent with isotropic orbits, whereas the TOs for NATs with d less than 500 kpc are consistent with highly radial orbits. If radial orbits were observed near the centers of other types of cluster galaxies as well, it could be inferred that violent relaxation during cluster formation was incomplete, and that clusters form by spherical collapse and secondary infall, as proposed by Gunn (1977).

O'Dea, Christopher P.↗
DOE OSTI2025

Galaxy-multiplet clustering from DESI DR2

We present an efficient estimator for higher-order galaxy clustering using small groups of nearby galaxies, or multiplets. Using the Luminous Red Galaxy (LRG) sample from the Dark Energy Spectroscopic Instrument (DESI) Data Release 2, we identify galaxy multiplets as discrete objects and measure their cross-correlations with the general galaxy field. Our results show that the multiplets exhibit stronger clustering bias as they trace more massive dark matter halos than individual galaxies. When comparing the observed clustering statistics with the mock catalogs generated from the N-body simulation AbacusSummit, we find that the mocks underpredict multiplet clustering despite reproducing the galaxy two-point auto-correlation reasonably well. This discrepancy indicates that the standard Halo Occupation Distribution (HOD) model is insufficient to describe the properties of galaxy multiplets, revealing the greater constraining power of this higher-order statistic on galaxy-halo connection and the possibility that multiplets are specific to additional assembly bias. We demonstrate that incorporating secondary biases into the HOD model improves agreement with the observed multiplet statistics, specifically by allowing galaxies to preferentially occupy halos in denser environments. Our results highlight the potential of utilizing multiplet clustering, beyond traditional two-point correlation measurements, to break degeneracies in models describing the galaxy-dark matter connection.

cosmology↗
DOE OSTI2026

Imaging systematics induced by galaxy subsample fluctuation: New systematics at second order

Imaging systematics refers to the inhomogeneous distribution of a galaxy sample caused by varying observing conditions and astrophysical foregrounds. Current mitigation methods correct the galaxy density fluctuations $n$ gal /$\bar{n}$ gal caused by imaging systematics assuming that all galaxies in a sample have the same $n$ gal /$\bar{n}$ gal . Under this assumption, the corrected sample cannot perfectly recover the true correlation function. Here, we name this effect subsample systematics. For a galaxy sample, even if its overall sample statistics [redshift distribution 𝑛⁡(𝑧), galaxy bias 𝑏⁡(𝑧)], are accurately measured, 𝑛⁡(𝑧), 𝑏⁡(𝑧) can still vary across the observed footprint. It makes the correlation function amplitude of galaxy clustering higher, while correlation functions for galaxy-galaxy lensing and cosmic shear do not have noticeable change. Such a combination could potentially degenerate with physical signals on small angular scales, such as the amplitude of galaxy clustering, the impact of neutrino mass on the matter power spectrum, etc. subsample systematics cannot be corrected using imaging systematics mitigation approaches that rely on the cross-correlation signal between imaging systematics maps and the observed galaxy density field. In this paper, we derive formulated expressions of subsample systematics, demonstrating its fundamental difference with other imaging systematics. We also provide several toy models to visualize this effect. Finally, we discuss a potential method to estimate and mitigate subsample systematics by forward modeling its behavior using synthetic source injection.

Kong, Hui [The Barcelona Institute of Science and ↗
DOE OSTI2024

Impact of survey spatial variability on galaxy redshift distributions and the cosmological 3 × 2-point statistics for the Rubin Legacy Survey of Space and Time (LSST)

We investigate the impact of spatial survey non-uniformity on the galaxy redshift distributions for forthcoming data releases of the Rubin Observatory Legacy Survey of Space and Time (LSST). Specifically, we construct a mock photometry data set degraded by the Rubin OpSim observing conditions, and estimate photometric redshifts of the sample using a template-fitting photo-z estimator, BPZ, and a machine learning method, FlexZBoost. We select the Gold sample, defined as $i\lt 25.3$ for 10 yr LSST data, with an adjusted magnitude cut for each year and divide it into five tomographic redshift bins for the weak lensing lens and source samples. We quantify the change in the number of objects, mean redshift, and width of each tomographic bin as a function of the coadd i-band depth for 1-yr (Y1), 3-yr (Y3), and 5-yr (Y5) data. In particular, Y3 and Y5 have large non-uniformity due to the rolling cadence of LSST, hence provide a worst-case scenario of the impact from non-uniformity. We find that these quantities typically increase with depth, and the variation can be $10\!-\!40~{{\rm per\ cent}}$ at extreme depth values. Using Y3 as an example, we propagate the variable depth effect to the weak lensing $3\times 2$ pt analysis, and assess the impact on cosmological parameters via a Fisher forecast. We find that galaxy clustering is most susceptible to variable depth, and non-uniformity needs to be mitigated below 3 per cent to recover unbiased cosmological constraints. There is little impact on galaxy–shear and shear–shear power spectra, given the expected LSST Y3 noise.

cosmology↗
DOE OSTI2021

Dark Energy Survey Y3 results: blending shear and redshift biases in image simulations

ABSTRACT As the statistical power of galaxy weak lensing reaches per cent level precision, large, realistic, and robust simulations are required to calibrate observational systematics, especially given the increased importance of object blending as survey depths increase. To capture the coupled effects of blending in both shear and photometric redshift calibration, we define the effective redshift distribution for lensing, nγ(z), and describe how to estimate it using image simulations. We use an extensive suite of tailored image simulations to characterize the performance of the shear estimation pipeline applied to the Dark Energy Survey (DES) Year 3 data set. We describe the multiband, multi-epoch simulations, and demonstrate their high level of realism through comparisons to the real DES data. We isolate the effects that generate shear calibration biases by running variations on our fiducial simulation, and find that blending-related effects are the dominant contribution to the mean multiplicative bias of approximately $-2{{\ \rm per\ cent}}$. By generating simulations with input shear signals that vary with redshift, we calibrate biases in our estimation of the effective redshift distribution, and demonstrate the importance of this approach when blending is present. We provide corrected effective redshift distributions that incorporate statistical and systematic uncertainties, ready for use in DES Year 3 weak lensing analyses.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2024

Galaxy Zoo DESI: large-scale bars as a secular mechanism for triggering AGNs

ABSTRACT Despite the evidence that supermassive black holes (SMBHs) co-evolve with their host galaxy, and that most of the growth of these SMBHs occurs via merger-free processes, the underlying mechanisms which drive this secular co-evolution are poorly understood. We investigate the role that both strong and weak large-scale galactic bars play in mediating this relationship. Using 48 871 disc galaxies in a volume-limited sample from Galaxy Zoo DESI, we analyse the active galactic nucleus (AGN) fraction in strongly barred, weakly barred, and unbarred galaxies up to $z = 0.1$ over a range of stellar masses and colours. After controlling for stellar mass and colour, we find that the optically selected AGN fraction is $31.6 \pm 0.9$ per cent in strongly barred galaxies, $23.3 \pm 0.8$ per cent in weakly barred galaxies, and $14.2 \pm 0.6$ per cent in unbarred disc galaxies. These are highly statistically robust results, strengthening the tantalizing results in earlier works. Strongly barred galaxies have a higher fraction of AGNs than weakly barred galaxies, which in turn have a higher fraction than unbarred galaxies. Thus, while bars are not required in order to grow an SMBH in a disc galaxy, large-scale galactic bars appear to facilitate AGN fuelling, and the presence of a strong bar makes a disc galaxy more than twice as likely to host an AGN than an unbarred galaxy at all galaxy stellar masses and colours.

Astronomy & Astrophysics↗
NASA NTRS1985

IRAS observations of active galaxies

The IRAS survey gives an unbiased view of the infrared properties of the active galaxies. Seyfert galaxies occupy much the same area in color-color plots as to normal infrared bright galaxies, but extend the range towards flatter 60 to 25 mm slopes. Statistically the Seyfert 1 galaxies can be distinguished from the Seyfert 2 galaxies, lying predominantly closer to the area with constant slopes between 25 and 200 mm. The infrared measurements of the Seyfert galaxies cannot distinguish between the emission mechanisms in these objects although they agree with the currently popular ideas; they do provide a measure of the total luminosity of the Seyferts. The quasar's position in the color-color diagrams continue the trend of the Seyferts. The quasar 3C48 is shown to be exceptional among the radio loud quasars in that it has a high infrared luminosity which dominates the power output of the quasar and is most likely associated with the underlying host galaxy.

Neugebauer, G.↗
NASA NTRS1985

On percolation as a cosmological test

Difficulties in the use of percolation as a complementary statistic for the galaxy clustering pattern are pointed out by studying simple toy models and dynamical N-body models that represent the competing clustering scenarios. The percolation properties are found not to be very sensitive to the presence of pancakes and strings once they are clumpy, and hence they do not distinguish properly between models that are very different. In the case of very smooth pancakes, the ability to percolate depends on sampling parameters, such as the mean number density and the volume, in a way which is unknown a priori because it depends on the same properties that the test ought to measure. This problem could, in principle, be eased by using volume-limited samples of high mean number density (an order of magnitude denser than the CfA redshift survey volume limited at 4000 km/s) and by comparing to models of identical number density and volume. An alternative approach, based on the sampling effects themselves, may provide a qualitative test for pancakes in samples of lower densities.

Dekel, A.↗
NASA NTRS1986

Radio properties of type 1.8 and 1.9 Seyfert galaxies

A number of type 1.8 and 1.9 Seyfert galaxies have been observed at the VLA in order to compare their properties with those of the other types of Seyfert galaxy. The observed types have radio luminosities in the range of 10 to the 39th-40.5th args/s, with the median near 10 to the 40th ergs/s. Most of these galaxies have radio sources with diameters of about 500 pc or less. The ratio of radio luminosity to featureless optical continuum luminosity in the Seyfert 1.8/12.9 galaxies and Seyfert 1.2/1.5 galaxies is intermediate between the values for Seyfert 1 and Seyfert 2 galaxies. The infrared-to-radio ratio decreases along the sequence from Seyfert 1 galaxies, through intermediate Seyfert galaxies, to Seyfert 2 galaxies. This systematic statistical difference in the ratio of two aspect-independent quantities implies that the differences among the Seyfert classes cannot be attributed solely to differences in viewing angle.

Ulvestad, James S.↗