Searcharxiv⌕ Search

arXiv subjects

Edward L. Wright

Publications and source records attributed to Edward L. Wright.

At least 55 records · Page 3Linked to original sources

Interferometric Follow-Up of WISE Hyper-Luminous Hot, Dust-Obscured Galaxies

WISE has discovered an extraordinary population of hyper-luminous dusty galaxies which are faint in the two bluer passbands ($3.4\, μ$m and $4.6\, μ$m) but are bright in the two redder passbands of WISE ($12\, μ$m and $22\, μ$m). We report on initial follow-up observations of three of these hot, dust-obscured galaxies, or Hot DOGs, using the CARMA and SMA interferometer arrays at submm/mm wavelengths. We report continuum detections at $\sim$ 1.3 mm of two sources (WISE J014946.17+235014.5 and WISE J223810.20+265319.7, hereafter W0149+2350 and W2238+2653, respectively), and upper limits to CO line emission at 3 mm in the observed frame for two sources (W0149+2350 and WISE J181417.29+341224.8, hereafter W1814+3412). The 1.3 mm continuum images have a resolution of 1-2 arcsec and are consistent with single point sources. We estimate the masses of cold dust are 2.0$\times 10^{8} M_{\odot}$ for W0149+2350 and 3.9$\times 10^{8} M_{\odot}$ for W2238+2653, comparable to cold dust masses of luminous quasars. We obtain 2$σ$ upper limits to the molecular gas masses traced by CO, which are 3.3$\times 10^{10} M_{\odot}$ and 2.3$\times 10^{10} M_{\odot}$ for W0149+2350 and W1814+3412, respectively. We also present high-resolution, near-IR imaging with WFC3 on the Hubble Space Telescope for W0149+2653 and with NIRC2 on Keck for W2238+2653. The near-IR images show morphological structure dominated by a single, centrally condensed source with effective radius less than 4 kpc. No signs of gravitational lensing are evident.

astro-ph.GA↗

NEOWISE-R Observation of the Coolest Known Brown Dwarf

The Wide-field Infrared Survey Explorer (WISE) spacecraft has been reactivated as NEOWISE-R to characterize and search for Near Earth Objects. The brown dwarf WISE J085510.83-071442.5 has now been reobserved by NEOWISE-R, and we confirm the results of Luhman (2014b), who found a very low effective temperature ($\approx 250$ K), a very high proper motion (8.1 +/- 0.1 arcsec/yr) , and a large parallax (454 +/- 45 mas). The large proper motion has separated the brown dwarf from the background sources that influenced the 2010 WISE data, allowing a measurement of a very red WISE color of W1-W2 $> 3.9$ mag. A re-analysis of the 2010 WISE astrometry using only the W2 band, combined with the new NEOWISE-R 2014 position, gives an improved parallax of 448 +/- 33 mas and proper motion of 8.08 +/- 0.05\; arcsec/yr. These are all consistent with Luhman (2014b).

astro-ph.SR↗

Submillimetre observations of WISE-selected high-redshift, luminous, dusty galaxies

We present SCUBA-2 850um submillimetre (submm) observations of the fields of 10 dusty, luminous galaxies at z ~ 1.7 - 4.6, detected at 12um and/or 22um by the WISE all-sky survey, but faint or undetected at 3.4um and 4.6um; dubbed hot, dust-obscured galaxies (Hot DOGs). The six detected targets all have total infrared luminosities greater than 10^13 L_sun, with one greater than 10^14 L_sun. Their spectral energy distributions (SEDs) are very blue from mid-infrared to submm wavelengths and not well fitted by standard AGN SED templates, without adding extra dust extinction to fit the WISE 3.4um and 4.6um data. The SCUBA-2 850um observations confirm that the Hot DOGs have less cold and/or more warm dust emission than standard AGN templates, and limit an underlying extended spiral or ULIRG-type galaxy to contribute less than about 2% or 55% of the typical total Hot DOG IR luminosity, respectively. The two most distant and luminous targets have similar observed submm to mid-infrared ratios to the rest, and thus appear to have even hotter SEDs. The number of serendipitous submm galaxies (SMGs) detected in the 1.5-arcmin-radius SCUBA-2 850um maps indicates there is a significant over-density of serendipitous sources around Hot DOGs. These submm observations confirm that the WISE-selected ultra-luminous galaxies have very blue mid-infrared to submm SEDs, suggesting that they contain very powerful AGN, and are apparently located in unusual arcmin-scale overdensities of very luminous dusty galaxies.

astro-ph.GA↗

The AllWISE Motion Survey and The Quest for Cold Subdwarfs

The AllWISE processing pipeline has measured motions for all objects detected on WISE images taken between 2010 January and 2011 February. In this paper, we discuss new capabilities made to the software pipeline in order to make motion measurements possible, and we characterize the resulting data products for use by future researchers. Using a stringent set of selection criteria, we find 22,445 objects that have significant AllWISE motions, of which 3,525 have motions that can be independently confirmed from earlier 2MASS images yet lack any published motions in SIMBAD. Another 58 sources lack 2MASS counterparts and are presented as motion candidates only. Limited spectroscopic follow-up of this list has already revealed eight new L subdwarfs. These may provide the first hints of a "subdwarf gap" at mid-L types that would indicate the break between the stellar and substellar populations at low metallicities (i.e., old ages). Another object in the motion list -- WISEA J154045.67-510139.3 -- is a bright (J ~ 9 mag) object of type M6; both the spectrophotometric distance and a crude preliminary parallax place it ~6 pc from the Sun. We also compare our list of motion objects to the recently published list of 762 WISE motion objects from Luhman (2014). While these first large motion studies with WISE data have been very successful in revealing previously overlooked nearby dwarfs, both studies missed objects that the other found, demonstrating that many other nearby objects likely await discovery in the AllWISE data products.

astro-ph.SR↗

The First AllWISE Proper Motion Discovery: WISEA J070720.50+170532.7

While quality checking a new motion-aware co-addition of all 12.5 months of WISE data, the source WISE J070720.48+170533.0 was found to have moved 0.9 arc-sec in 6 months. Backtracking this motion allowed us to identify this source as 2MASS J07071961+1705464 and with several entries in the USNO B catalog. An astrometric fit to these archival data gives a proper motion of 1793 +/- 2 mas/yr and a parallax of 35 +/- 42 mas. Photometry from WISE, 2MASS and the POSS can be fit reasonably well by a blackbody with T = 3658 K and an angular radius of 4.36E-11 radians. No clear evidence of H_2 collision-induced absorption is seen in the near-IR. An optical spectrum shows broad deep CaH bands at 638 and 690 nm, broad deep Na D at 598.2 nm, and weak or absent TiO, indicating that this source is an ultra-subdwarf M star with a radial velocity about -21 +/- 18 km/sec relative to the Sun. Given its apparent magnitude, the distance is about 39 +/- 9 pc and the tangential velocity is probably about 330 km/sec, but a more precise parallax is needed to be certain.

astro-ph.SR↗

WISE Discovery of Hyper Luminous Galaxies at z=2-4 and Their Implications for Galaxy and AGN Evolution

On behalf of the WISE Science team, we present the discovery of a class of distant dust-enshrouded galaxies with extremely high luminosity. These galaxies are selected to have extreme red colors in the mid-IR using NASA's Wide-field Infrared Survey Explorer (WISE). They are faint in the optical and near-IR, predominantly at z=2-4, and with IR luminosity > $10^{13}\, L_{Sun}$, making them Hyper-Luminous Infrared Galaxies (HyLIRGs). SEDs incorporating the WISE, Spitzer, and Herschel PACS and SPIRE photometry indicate hot dust dominates the bolometric luminosity, presumably powered by AGN. Preliminary multi-wavelength follow-up suggests that they are different from normal populations in the local M-sigma relation. Their low source density implies that these objects are either intrinsically rare, or a short-lived phase in a more numerous population. If the latter is the case, these hot, dust-enshrouded galaxies may be an early stage in the interplay between AGN and galaxies.

astro-ph.CO↗

The Exemplar T8 Subdwarf Companion of Wolf 1130

We have discovered a wide separation (188.5") T8 subdwarf companion to the sdM1.5+WD binary Wolf 1130. Companionship of WISE J200520.38+542433.9 is verified through common proper motion over a ~3 year baseline. Wolf 1130 is located 15.83 +/- 0.96 parsecs from the Sun, placing the brown dwarf at a projected separation of ~3000 AU. Near-infrared colors and medium resolution (R~2000-4000) spectroscopy establish the uniqueness of this system as a high-gravity, low-metallicity benchmark. Although there are a number of low-metallicity T dwarfs in the literature, WISE J200520.38+542433.9 has the most extreme inferred metallicity to date with [Fe/H] = -0.64 +/- 0.17 based on Wolf 1130. Model comparisons to this exemplar late-type subdwarf support it having an old age, a low metallicity, and a small radius. However, the spectroscopic peculiarities of WISE J200520.38+542433.9 underscore the importance of developing the low-metallicity parameter space of the most current atmospheric models.

astro-ph.SR↗

Centaurs and Scattered Disk Objects in the Thermal Infrared: Analysis of WISE/NEOWISE Observations

The Wide-field Infrared Survey Explorer (WISE) observed 52 Centaurs and Scattered Disk Objects in the thermal infrared, including the 15 discoveries that were new. We present analyses of these observations to estimate sizes and mean optical albedos. We find mean albedos of 0.08 +/- 0.04 for the entire data set. Thermal fits yield average beaming parameters of 0.9 +/- 0.2 that are similar for both SDO and Centaur sub-classes. Biased cumulative size distributions yield size-frequency distribution power law indices ~ -1.7 +/- 0.3. The data also reveal a relation between albedo and color at the 3-sigma level. No significant relation between diameter and albedos is found.

astro-ph.EP↗

Nearby M, L, and T Dwarfs Discovered by the Wide-field Infrared Survey Explorer (WISE)

In our effort to complete the census of low-mass stars and brown dwarfs in the immediate Solar Neighborhood, we present spectra, photometry, proper motions, and distance estimates for forty-two low-mass star and brown dwarf candidates discovered by the Wide-field Infrared Survey Explorer (WISE). We also present additional follow-up information on twelve candidates selected using WISE data but previously published elsewhere. The new discoveries include fifteen M dwarfs, seventeen L dwarfs, five T dwarfs, and five objects of other type. Among these discoveries is a newly identified "unusually red L dwarf" (WISE J223527.07+451140.9), four peculiar L dwarfs whose spectra are most readily explained as unresolved L+T binary systems, and a T9 dwarf (WISE J124309.61+844547.8). We also show that the recently discovered red L dwarf WISEP J004701.06+680352.1 (Gizis et al. 2012) may be a low-gravity object and hence young and potentially low mass (< 25 MJup).

astro-ph.SR↗

Detection of a Nearby Halo Debris Stream in the WISE and 2MASS Surveys

Combining the Wide-Field Infrared Survey Explorer All-Sky Release with the 2MASS Point Source Catalog, we detect a nearby, moderately metal-poor stellar debris stream spanning 24 degrees across the southern sky. The stream, which we designate Alpheus, is at an estimated distance of ~1.9 kpc. Its position, orientation, width, estimated metallicity, and to some extent its distance, are in approximate agreement with what one might expect of the leading tidal tail of the southern globular cluster NGC 288.

astro-ph.GA↗

A Study of the Diverse T Dwarf Population Revealed by WISE

We report the discovery of 87 new T dwarfs uncovered with the Wide-field Infrared Survey Explorer (WISE) and three brown dwarfs with extremely red near-infrared colors that exhibit characteristics of both L and T dwarfs. Two of the new T dwarfs are likely binaries with L7+/-1 primaries and mid-type T secondaries. In addition, our follow-up program has confirmed 10 previously identified T dwarfs and four photometrically-selected L and T dwarf candidates in the literature. This sample, along with the previous WISE discoveries, triples the number of known brown dwarfs with spectral types later than T5. Using the WISE All-Sky Source Catalog we present updated color-color and color-type diagrams for all the WISE-discovered T and Y dwarfs. Near-infrared spectra of the new discoveries are presented, along with spectral classifications. To accommodate later T dwarfs we have modified the integrated flux method of determining spectral indices to instead use the median flux. Furthermore, a newly defined J-narrow index differentiates the early-type Y dwarfs from late-type T dwarfs based on the J-band continuum slope. The K/J indices for this expanded sample show that 32% of late-type T dwarfs have suppressed K-band flux and are blue relative to the spectral standards, while only 11% are redder than the standards. Comparison of the Y/J and K/J index to models suggests diverse atmospheric conditions and supports the possible re-emergence of clouds after the L/T transition. We also discuss peculiar brown dwarfs and candidates that were found not to be substellar, including two Young Stellar Objects and two Active Galactic Nuclei. The coolest WISE-discovered brown dwarfs are the closest of their type and will remain the only sample of their kind for many years to come.

astro-ph.SR↗

A T8.5 Brown Dwarf Member of the Xi Ursae Majoris System

The Wide-field Infrared Survey Explorer has revealed a T8.5 brown dwarf (WISE J111838.70+312537.9) that exhibits common proper motion with a solar-neighborhood (8 pc) quadruple star system - Xi Ursae Majoris. The angular separation is 8.5 arc-min, and the projected physical separation is about 4000 AU. The sub-solar metallicity and low chromospheric activity of Xi UMa A argue that the system has an age of at least 2 Gyr. The infrared luminosity and color of the brown dwarf suggests the mass of this companion ranges between 14 and 38 Jupiter masses for system ages of 2 and 8 Gyr respectively.

astro-ph.SR↗

Parallaxes and Proper Motions of Ultracool Brown Dwarfs of Spectral Types Y and Late T

We present astrometric measurements of eleven nearby ultracool brown dwarfs of spectral types Y and late-T, based on imaging observations from a variety of space-based and ground-based telescopes. These measurements have been used to estimate relative parallaxes and proper motions via maximum likelihood fitting of geometric model curves. To compensate for the modest statistical significance (<~ 7) of our parallax measurements we have employed a novel Bayesian procedure for distance estimation which makes use of an a priori distribution of tangential velocities, Vtan, assumed similar to that implied by previous observations of T dwarfs. Our estimated distances are therefore somewhat dependent on that assumption. Nevertheless, the results have yielded distances for five of our eight Y dwarfs and all three T dwarfs. Estimated distances in all cases are >~ 3 pc. In addition, we have obtained significant estimates of Vtan for two of the Y dwarfs; both are <100 km/s, consistent with membership in the thin disk population. Comparison of absolute magnitudes with model predictions as a function of color shows that the Y dwarfs are significantly redder in J-H than predicted by a cloud-free model

astro-ph.SR↗

The Faint End of the Cluster Galaxy Luminosity Function at High Redshift

We measure the faint end slope of the galaxy luminosity function (LF) for cluster galaxies at 1<z<1.5 using Spitzer IRAC data. We investigate whether this slope, alpha, differs from that of the field LF at these redshifts, and with the cluster LF at low redshifts. The latter is of particular interest as low-luminosity galaxies are expected to undergo significant evolution. We use seven high-redshift spectroscopically confirmed galaxy clusters drawn from the IRAC Shallow Cluster Survey to measure the cluster galaxy LF down to depths of M* + 3 (3.6 microns) and M* + 2.5 (4.5 microns). The summed LF at our median cluster redshift (z=1.35) is well fit by a Schechter distribution with alpha[3.6] = -0.97 +/- 0.14 and alpha[4.5] = -0.91 +/- 0.28, consistent with a flat faint end slope and is in agreement with measurements of the field LF in similar bands at these redshifts. A comparison to alpha in low-redshift clusters finds no statistically significant evidence of evolution. Combined with past studies which show that M* is passively evolving out to z~1.3, this means that the shape of the cluster LF is largely in place by z~1.3. This suggests that the processes that govern the build up of the mass of low-mass cluster galaxies have no net effect on the faint end slope of the cluster LF at z<1.3.

astro-ph.CO↗

A measurement of the intrahalo light fraction with near-infrared background anisotropies

Unresolved near-infrared background anisotropies are expected to have contributions from the earliest galaxies during reionization and faint, dwarf galaxies at intermediate redshifts. Previous measurements were unable to conclusively pinpoint the dominant origin because they did not sample spatial scales that were sufficiently large to distinguish between these two possibilities. Here we report a measurement of the anisotropy power spectrum from sub-arcminute to one degree angular scales and find the clustering amplitude to be larger than the model predictions involving the two existing explanations. As the shot-noise level of the power spectrum is consistent with that expected from faint galaxies, a new source population on the sky is not necessary to explain the observations. A physical mechanism that increases the clustering amplitude, however, is needed. Motivated by recent results related to the extended stellar light profile in dark matter halos, we consider the possibility that the fluctuations originate from diffuse intrahalo stars of all galaxies. We find that the measured power spectrum can be explained by an intrahalo light fraction of 0.07 to 0.2 % relative to the total luminosity in dark matter halos of masses log(M/M_Sun) ~ 9 to 12 at redshifts of ~ 1 to 4.

astro-ph.CO↗

The Massive Distant Clusters of WISE Survey: The First Distant Galaxy Cluster Discovered by WISE

We present spectroscopic confirmation of a z=0.99 galaxy cluster discovered using data from the Wide-field Infrared Survey Explorer (WISE). This is the first z~1 cluster candidate from the Massive Distant Clusters of WISE Survey (MaDCoWS) to be confirmed. It was selected as an overdensity of probable z>~1 sources using a combination of WISE and SDSS-DR8 photometric catalogs. Deeper follow-up imaging data from Subaru and WIYN reveal the cluster to be a rich system of galaxies, and multi-object spectroscopic observations from Keck confirm five cluster members at z=0.99. The detection and confirmation of this cluster represents a first step towards constructing a uniformly-selected sample of distant, high-mass galaxy clusters over the full extragalactic sky using WISE data.

astro-ph.CO↗

WISE J163940.83-684738.6: A Y Dwarf identified by Methane Imaging

We have used methane imaging techniques to identify the near-infrared counterpart of the bright WISE source WISEJ163940.83-684738.6. The large proper motion of this source (around 3.0arcsec/yr) has moved it, since its original WISE identification, very close to a much brighter background star -- it currently lies within 1.5" of the J=14.90+-0.04 star 2MASS16394085-6847446. Observations in good seeing conditions using methane sensitive filters in the near-infrared J-band with the FourStar instrument on the Magellan 6.5m Baade telescope, however, have enabled us to detect a near-infrared counterpart. We have defined a photometric system for use with the FourStar J2 and J3 filters, and this photometry indicates strong methane absorption, which unequivocally identifies it as the source of the WISE flux. Using these imaging observations we were then able to steer this object down the slit of the FIRE spectrograph on a night of 0.6" seeing, and so obtain near-infrared spectroscopy confirming a Y0-Y0.5 spectral type. This is in line with the object's near-infrared-to-WISE J3--W2 colour. Preliminary astrometry using both WISE and FourStar data indicates a distance of 5.0+-0.5pc and a substantial tangential velocity of 73+-8km/s. WISEJ163940.83-684738.6 is the brightest confirmed Y dwarf in the WISE W2 passband and its distance measurement places it amongst the lowest luminosity sources detected to date.

astro-ph.SR↗

WISE/NEOWISE Preliminary Analysis and Highlights of the 67P/Churyumov-Gerasimenko Near Nucleus Environs

On January 18-19 and June 28-29 of 2010, the Wide-field Infrared Survey Explorer (WISE) spacecraft imaged the Rosetta mission target, comet 67P/Churyumov-Gerasimenko. We present a preliminary analysis of the images, which provide a characterization of the dust environment at heliocentric distances similar to those planned for the initial spacecraft encounter, but on the outbound leg of its orbit rather than the inbound. Broad-band photometry yields low levels of CO2 production at a comet heliocentric distance of 3.32 AU and no detectable production at 4.18 AU. We find that at these heliocentric distances, large dust grains with mean grain diameters on the order of a millimeter or greater dominate the coma and evolve to populate the tail. This is further supported by broad-band photometry centered on the nucleus, which yield an estimated differential dust particle size distribution with a power law relation that is considerably shallower than average. We set a 3-sigma upper limit constraint on the albedo of the large-grain dust at <= 0.12. Our best estimate of the nucleus radius (1.82 +/- 0.20 km) and albedo (0.04 +/- 0.01) are in agreement with measurements previously reported in the literature.

astro-ph.EP↗