On the ages of the stellar populations of galaxies at z = 0.1–7
Explore the source record for details and available documents.
Eric E Martínez-García↗
SEARCH · Engineering Papers
Results for “E+A galaxies”
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.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Dark Energy Survey Year 6 results: cell-based coadds and METADETECTION weak lensing shape catalogue
We present the metadetection weak lensing galaxy shape catalogue from the 6-yr Dark Energy Survey (DES Y6) imaging data. This data set is the final release from DES, spanning 4422 deg 2 of the southern sky. We describe how the catalogue was constructed, including the two new major processing steps, cell-based image coaddition, and shear measurements with metadetection. The DES Y6 M etadetection weak lensing shape catalogue consists of 151 922 791 galaxies detected over riz bands, with an effective number density of n eff = 8.22 galaxies per arcmin 2 and shape noise of σ e = 0.29. We carry out a suite of validation tests on the catalogue, including testing for point spread function (PSF) leakage, testing for the impact of PSF modelling errors, and testing the correlation of the shear measurements with galaxy, PSF, and survey properties. In addition to demonstrating that our catalogue is robust for weak lensing science, we use the DES Y6 image simulation suite to estimate the overall multiplicative shear bias of our shear measurement pipeline. We find no detectable multiplicative bias at the roughly half-per cent level, with m = (3.4 ± 6.1) x 10 –3 , at 3σ uncertainty. This is the first time both cell-based coaddition and Metadetection algorithms are applied to observational data, paving the way to the Stage-IV weak lensing surveys.
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
The Caltech-NRAO Stripe 82 Survey (CNSS) Paper. I. The Pilot Radio Transient Survey in 50 Deg.(exp. 2)
We have commenced a multiyear program, the Caltech-NRAO Stripe 82 Survey (CNSS), to search for radio transients with the Jansky VLA in the Sloan Digital Sky Survey Stripe 82 region. The CNSS will deliver five epochs over the entire approx. 270 deg.(exp. 2) of Stripe 82, an eventual deep combined map with an rms noise of approx. 40 proper motion epoch y and catalogs at a frequency of 3 GHz, and having a spatial resolution of 3 inches. This first paper presents the results from an initial pilot survey of a 50 deg.(exp. 2) region of Stripe 82, involving four epochs spanning logarithmic timescales between 1 week and 1.5 yr, with the combined map having a median rms noise of 35 proper motion epoch y. This pilot survey enabled the development of the hardware and software for rapid data processing, as well as transient detection and follow-up, necessary for the full 270 deg.(exp. 2) survey. Data editing, calibration, imaging, source extraction, cataloging, and transient identification were completed in a semi-automated fashion within 6 hr of completion of each epoch of observations, using dedicated computational hardware at the NRAO in Socorro and custom-developed data reduction and transient detection pipelines. Classification of variable and transient sources relied heavily on the wealth of multiwavelength legacy survey data in the Stripe 82 region, supplemented by repeated mapping of the region by the Palomar Transient Factory. A total of 3.9(+0.5%/-0.9%) of the few thousand detected point sources werefound to vary by greater than 30%, consistent with similar studies at 1.4 and 5 GHz. Multiwavelength photometric data and light curves suggest that the variability is mostly due to shock-induced flaring in the jets of active galactic nuclei (AGNs). Although this was only a pilot survey, we detected two bona fide transients, associated with an RS CVn binary and a dKe star. Comparison with existing legacy survey data (FIRST, VLA-Stripe 82) revealed additional highly variable and transient sources on timescales between 5 and 20 yr, largely associated with renewed AGN activity. The rates of such AGNs possibly imply episodes of enhanced accretion and jet activity occurring once every approx. 40,000 yr in these galaxies. We compile the revised radio transient rates and make recommendations for future transient surveys and joint radio-optical experiments.
galaxies: active – radio continuum: galaxies –↗
Hubble Space Telescope Observations of the Afterglow, Supernova and Host Galaxy Associated with the Extremely Bright GRB 130427A
We present Hubble Space Telescope (HST) observations of the exceptionally bright and luminous Swift gamma-ray burst, GRB 130427A. At z=0.34 this burst affords an excellent opportunity to study the supernova and host galaxy associated with an intrinsically extremely luminous burst (E(sub iso) greater than 10(exp 54) erg): more luminous than any previous GRB with a spectroscopically associated supernova. We use the combination of the image quality, UV capability and and invariant PSF of HST to provide the best possible separation of the afterglow, host and supernova contributions to the observed light approximately 17 rest-frame days after the burst utilising a host subtraction spectrum obtained 1 year later. Advanced Camera for Surveys (ACS) grism observations show that the associated supernova, SN 2013cq, has an overall spectral shape and luminosity similar to SN 1998bw (with a photospheric velocity, vph approximately 15,000 kilometers per second). The positions of the bluer features are better matched by the higher velocity SN 2010bh (vph approximately 30,000 kilometers per second), but SN 2010bh (vph approximately 30,000 kilometers per second but this SN is significantly fainter, and fails to reproduce the overall spectral shape, perhaps indicative of velocity structure in the ejecta. We find that the burst originated approximately 4 kpc from the nucleus of a moderately star forming (1 Solar Mass yr(exp-1)), possibly interacting disc galaxy. The absolute magnitude, physical size and morphology of this galaxy, as well as the location of the GRB within it are also strikingly similar to those of GRB980425SN 1998bw. The similarity of supernovae and environment from both the most luminous and least luminous GRBs suggests broadly similar progenitor stars can create GRBs across six orders of magnitude in isotropic energy.
host↗
Far-Infrared Spectroscopy of M82: Interstellar Properties of the Dual Nuclear Starbursts
We have measured [O I] 63 mm and [Si II] 35 mm in the central 44' (700 pc) of the starburst galaxy M82. The luminosities in these transitions are each ~0.1 percent of the bolometric luminosity. We model the [O I] in M82 as arising from warm neutral gas photodissociated by FUV flux from OB stars, while most of the [Si II] emission arises from associated H II regions.!.
spectroscopy starburst galaxy luminosity↗
Evidence for Black Holes in Green Peas from WISE Colors and Variability
We explore the presence of active galactic nuclei (AGNs)/black holes in Green Pea galaxies (GPs), motivated by the presence of high-ionization emission lines such as He ii and [Ne iii] in their optical spectra. In order to identify AGN candidates, we used mid-infrared (MIR) photometric observations from the all-sky Wide-field Infrared Survey Explorer (WISE) mission for a sample of 1004 GPs. Considering only >5σ detections with no contamination from neighboring sources in AllWISE, we select 31 GPs out of 134 as candidate AGNs based on a stringent three-band WISE color diagnostic. Using multi-epoch photometry in W1 and W2 bands based on time-resolved unWISE coadd images, we find two sources exhibiting variability in both the WISE bands among 112 GPs with W1 ≤16 mag and no contamination from neighboring sources in unWISE. These two variable sources were selected as AGNs by the WISE three-band color diagnostic as well. Compared to variable AGN fractions observed among low-mass galaxy samples in previous studies, we find a higher fraction (~1.8%) of MIR variable sources among GPs, which demonstrates the uniqueness and importance of studying these extreme objects. Through this work, we demonstrate that MIR diagnostics are promising tools to select AGNs that may be missed by other selection techniques (including optical emission-line ratios and X-ray emission) in star formation-dominated, low-mass, low-metallicity galaxies.
79 ASTRONOMY AND ASTROPHYSICS↗
Dark energy survey year 3 results: weak lensing shape catalogue
ABSTRACT We present and characterize the galaxy shape catalogue from the first 3 yr of Dark Energy Survey (DES) observations, over an effective area of 4143 deg2 of the southern sky. We describe our data analysis process and our self-calibrating shear measurement pipeline metacalibration, which builds and improves upon the pipeline used in the DES Year 1 analysis in several aspects. The DES Year 3 weak-lensing shape catalogue consists of 100 204 026 galaxies, measured in the riz bands, resulting in a weighted source number density of neff = 5.59 gal arcmin−2 and corresponding shape noise σe = 0.261. We perform a battery of internal null tests on the catalogue, including tests on systematics related to the point spread function (PSF) modelling, spurious catalogue B-mode signals, catalogue contamination, and galaxy properties.
79 ASTRONOMY AND ASTROPHYSICS↗
Streams, Shells, and Substructures in the Accretion-Built Stellar Halo of NGC 300
We present deep optical observations of the stellar halo of NGC 300, an LMC-mass galaxy, acquired with the DEEP sub-component of the DECam Local Volume Exploration survey (DELVE) using the 4 m Blanco Telescope. Our resolved star analysis reveals a large, low surface brightness stellar stream ($M_{V}\sim-8.5$; [Fe/H] $= -1.4\pm0.15$) extending more than 40 kpc north from the galaxy's center. We also find other halo structures, including potentially an additional stream wrap to the south, which may be associated with the main stream. The morphology and derived low metallicities of the streams and shells discovered surrounding NGC 300 are highly suggestive of a past accretion event. Assuming a single progenitor, the accreted system is approximately Fornax-like in luminosity, with an inferred mass ratio to NGC 300 of approximately $1:15$. We also present the discovery of a metal-poor globular cluster ($R_{\rm{proj}}=23.3$~kpc; $M_{V}=-8.99\pm0.16$; [Fe/H] $\approx-1.6\pm0.6$) in the halo of NGC 300, the furthest identified globular cluster associated with NGC 300. The stellar structures around NGC 300 represent the richest features observed in a Magellanic Cloud analog to date, strongly supporting the idea that accretion and subsequent disruption is an important mechanism in the assembly of dwarf galaxy stellar halos.
79 ASTRONOMY AND ASTROPHYSICS↗
The optical object identified with 3C 455.
It is shown that the optical object identified with 3C 455 is a quasi-stellar object with a redshift z = 0.543. The QSO is situated 23 sec northeast of the S0 galaxy NGC 7413, which has a redshift of 0.0332. It is pointed out that the discovery of the present object in a position so close to a galaxy is further evidence in favor of the existence of a physical association between 3C QSOs and bright galaxies.
Arp, H. C.↗
Shakhbazian I - A distant cluster of compact galaxies.
Shakhbazian (1957) reported a cluster of red objects which he interpreted to be a cluster of stars in Ursa Major at a distance of 130 kpc. Spectra obtained with an image-tube scanner for 5 members of this cluster show that they are all galaxies with a redshift corresponding to a radial velocity 29.700 km/sec. The remaining 12 members of the group appear to be diffuse, and are probably also galaxies.
Robinson, L. B.↗
The elemental abundance ratios of interstellar secondary and primary cosmic rays
We report new observations of abundances in the charge range (Z) between 2 and 10, which were obtained with a dE/dx-Cerenkov detector launched into a polar orbit on OGO-6 as part of the Caltech Solar and Galactic Cosmic Ray Experiment. Integral rigidity spectra of all the elements observed have shapes similar to that of the helium spectrum in the rigidity range of 2 to 14 GV, approaching a power law with exponent -1.6 above 8 GV. Calculations of interstellar propagation assuming a steady-state model and including the presence of interstellar helium and the effects of solar modulation predict a variation with rigidity of ratios such as Be-O and B/O, which is not observed. The data can be explained by assuming a rigidity-dependent confinement of cosmic rays within the Galaxy.
Brown, J. W.↗
Neutral hydrogen emission and absorption in three active Irr II galaxies
Peak optical H I absorption depths of 10% are found in a neutral hydrogen emission-absorption study of the active-nucleus Irr II galaxies NGC 520, 5363, and 5506. It is suggested that the absorption is due to a few standard clouds within several hundred parsecs of the nucleus, in the narrow-line emission region. The width of the absorption features is interpreted as being due to random motions of the gas within the absorbing clouds, in contrast to the large widths of the emission features that are due to the overall rotation of the galaxy.
Thuan, T. X.↗
The 2 micron spectrum of NGC 6240 - Evidence for more than a starburst
The exceptionally luminous interacting galaxy NGC 6240 has been studied with infrared spectroscopy and photometry. Emission lines of molecular hydrogen and the Paschen-alpha line of ionized hydrogen have been detected. Broad-band 10 micron and 20 micron emission has also been observed. Combined with previous optical spectroscopy and results from IRAS, the observations show that NGC 6240 cannot be explained along the lines of a superstarburst of massive stars such as seen in M82. It may be more easily understood in terms of an active nucleus similar to Seyfert galaxies.
Depoy, D. L.↗
The appearance of primeval galaxies
The appearance of protogalaxies expected by current theories of structure formation is discussed. A review of when and how galaxies form is given, and the results of two numerical simulations of inhomogeneous galaxy formation are presented. These models are used to predict the abundance of primeval galaxies in observational surveys.
Baron, E.↗
Global and radial variations in the efficiency of massive star formation among galaxies
In order to determine the regions within galaxies which give rise to the most efficient star formation and to test the hypothesis that galaxies with high infrared luminosities per unit molecular mass are efficiently producing high mass stars, researchers have undertaken an H alpha imaging survey in galaxies whose CO distributions have been measured as part of the Five College Radio Astronomy Observatory (FCRAO) Extragalactic CO Survey. From these images researchers have derived global H alpha fluxes and distributions for comparison with far infrared radiation (FIR) fluxes and CO fluxes and distributions. Here, researchers present results on the global massive star formation efficiency (SFE = L sub H sub alpha/M(H2)) as a function of morphological type and environment, and on the radial distribution of the SFE within both peculiar and isolated galaxies. On the basis of comparison of the global L sub H sub alpha/M(H2) and L sub FIR/M(H2) for 111 galaxies, researchers conclude that environment rather than morphological type has the strongest effect on the global efficiency of massive star formation. Based on their study of a small sample, they find that the largest radial gradients are observed in the interacting/peculiar galaxies, indicating that environment affects the star formation efficiency within galaxies as well.
Allen, Lori E.↗
Origin of kinematic subsystems in elliptical galaxies
The formation of a counterrotating central gas disk in a merger of two gas-rich disk galaxies of equal mass is demonstrated. Such a structure may well account for the unusual gas kinematics found in the merger remnant NGC7252. Continued star formation in such gaseous disks may produce central components with decoupled kinematics resembling the cores of some elliptical galaxies.
Hernquist, Lars↗
X-Ray Probes of Cosmic Star-Formation History
In a previous paper we point out that the X-ray luminosity L(sub x) of a galaxy is driven by the evolution of its X-ray binary population and that the profile of L(sub x) with redshift can both serve as a diagnostic probe of the Star Formation Rate (SFR) profile and constrain evolutionary models for X-ray binaries. We update our previous work using a suite of more recently developed SFR profiles that span the currently plausible range. The first Chandra deep imaging results on L(sub x)-evolution are beginning to probe the SFR profile of bright spirals and the early results are consistent with predictions based on current SFR models. Using these new SFR profiles the resolution of the "birthrate problem" of lowmass X-ray binaries (LMXBs) and recycled, millisecond pulsars in terms of an evolving global SFR is more complete. We also discuss the possible impact of the variations in the SFR profile of individual galaxies.
Ghosh, Pranab↗
[The growth movements of moss protonemata under clinostatic and microgravity conditions]
Populations of dark-grown protonemata of moss Ceratodon purpureus wt-4 (Germany) and wt-U (Ukraine) were rotated on clinostat or flown in space (experiment "Protonema" aboard Bion-11, December 24, 1996-January 7, 1997) to determine the effects of altered gravity on orientation of protonemata growing filaments. Protonemata had been cultivated 8 days in vertical stationary position at dark to be transported to microgravity or placed in clinostat for the period of 14 days. In the ground control, protonemata demonstrated the negatively gravitropic growth (straight upwards in a bundle of compact filaments). The horizontal or circular rotation in clinostat and exposure to microgravity made filaments grow every each way within the substrate plane but with an apparent trend to rightward curling resulting in "spiral galaxies".
NASA Discipline Plant Biology↗