371 research outputs found
Examining electron-boson coupling using time-resolved spectroscopy
Nonequilibrium pump-probe time domain spectroscopies can become an important
tool to disentangle degrees of freedom whose coupling leads to broad structures
in the frequency domain. Here, using the time-resolved solution of a model
photoexcited electron-phonon system we show that the relaxational dynamics are
directly governed by the equilibrium self-energy so that the phonon frequency
sets a window for "slow" versus "fast" recovery. The overall temporal structure
of this relaxation spectroscopy allows for a reliable and quantitative
extraction of the electron-phonon coupling strength without requiring an
effective temperature model or making strong assumptions about the underlying
bare electronic band dispersion.Comment: 23 pages, 4 figures + Supplementary Material and movies, to appear in
PR
Comparative Proteomics of Tandem Mass Spectrometry Analyses for Bacterial Strains Identification and Differentiation
Multiaperture Photometry of Galaxies in the Coma Cluster
We present a set of photometry for 745 band selected
objects in a region centered on the core of the Coma
cluster. This includes 516 galaxies and is at least 80% complete to H=16, with
a spectroscopically complete sample of 111 cluster members (nearly all with
morphological classification) for . For each object we present total
\cite{kron80} magnitudes and aperture photometry. As an example, we use these
data to derive color-magnitude relations for Coma early-type galaxies, measure
the intrinsic scatter of these relations and its dependence on galaxy mass, and
address the issue of color gradients. We find that the color gradients are mild
and that the intrinsic scatter about the color-magnitude relation is small
( mag in and less than in , or ).
There is no evidence that the intrinsic scatter varies with galaxy luminosity,
suggesting that the cluster red sequence is established at early epochs over a
range of in stellar mass.Comment: 41 pages, 5 figures, 18 data tables attached to source files or
available on request from R. De propris. Accepted for publication in
Astrophysical Journal Supplement Serie
Assembly of the Red Sequence in Infrared-Selected Galaxy Clusters from the IRAC Shallow Cluster Survey
We present results for the assembly and star formation histories of massive
(~L*) red sequence galaxies in 11 spectroscopically confirmed,
infrared-selected galaxy clusters at 1.0 < z < 1.5, the precursors to
present-day massive clusters with M ~ 10^15 M_sun. Using rest-frame optical
photometry, we investigate evolution in the color and scatter of the red
sequence galaxy population, comparing with models of possible star formation
histories. In contrast to studies of central cluster galaxies at lower redshift
(z < 1), these data are clearly inconsistent with the continued evolution of
stars formed and assembled primarily at a single, much-earlier time.
Specifically, we find that the colors of massive cluster galaxies at z = 1.5
imply that the bulk of star formation occurred at z ~ 3, whereas by z = 1 their
colors imply formation at z ~ 2; therefore these galaxies exhibit approximately
the same luminosity-weighted stellar age at 1 < z < 1.5. This likely reflects
star formation that occurs over an extended period, the effects of significant
progenitor bias, or both. Our results generally indicate that massive cluster
galaxy populations began forming a significant mass of stars at z >~ 4,
contained some red spheroids by z ~ 1.5, and were actively assembling much of
their final mass during 1 < z < 2 in the form of younger stars. Qualitatively,
the slopes of the cluster color-magnitude relations are consistent with no
significant evolution relative to local clusters.Comment: 24 pages, 9 figures, accepted to Ap
Detection of a CMB decrement towards a cluster of mJy radiosources
We present the results of radio, optical and near-infrared observations of
the field of TOC J0233.3+3021, a cluster of milliJansky radiosources from the
TexOx Cluster survey. In an observation of this field with the Ryle Telescope
(RT) at 15 GHz, we measure a decrement in the cosmic microwave background (CMB)
of Jy on the RT's 0.65 k baseline. Using
optical and infrared imaging with the McDonald 2.7-m Smith Reflector, Calar
Alto 3.5-m telescope and UKIRT, we identify the host galaxies of five of the
radiosources and measure magnitudes of , , .
The CMB decrement is consistent with the Sunyaev-Zel'dovich (SZ) effect of a
massive cluster of galaxies, which if modelled as a spherical King profile of
core radius has a central temperature decrement
of K. The magnitudes and colours of the galaxies are consistent with
those of old ellipticals at . We therefore conclude that TOC
J0233.3+3021 is a massive, high redshift cluster. These observations add to the
growing evidence for a significant population of massive clusters at high
redshift, and demonstrate the effectiveness of combining searches for AGN
`signposts' to clusters with the redshift-independence of the SZ effect.Comment: Six pages; accepted for publication in MNRAS. Version with
full-resolution UV plot available from
http://www.mrao.cam.ac.uk/~garret/MB185.p
Spitzer Photometry of WISE-Selected Brown Dwarf and Hyper-Luminous Infrared Galaxy Candidates
We present Spitzer 3.6 and 4.5 m photometry and positions for a sample
of 1510 brown dwarf candidates identified by the WISE all-sky survey. Of these,
166 have been spectroscopically classified as objects with spectral types M(1),
L(7), T(146), and Y(12); Sixteen other objects are non-(sub)stellar in nature.
The remainder are most likely distant L and T dwarfs lacking spectroscopic
verification, other Y dwarf candidates still awaiting follow-up, and assorted
other objects whose Spitzer photometry reveals them to be background sources.
We present a catalog of Spitzer photometry for all astrophysical sources
identified in these fields and use this catalog to identify 7 fainter (4.5
m 17.0 mag) brown dwarf candidates, which are possibly wide-field
companions to the original WISE sources. To test this hypothesis, we use a
sample of 919 Spitzer observations around WISE-selected high-redshift
hyper-luminous infrared galaxy (HyLIRG) candidates. For this control sample we
find another 6 brown dwarf candidates, suggesting that the 7 companion
candidates are not physically associated. In fact, only one of these 7 Spitzer
brown dwarf candidates has a photometric distance estimate consistent with
being a companion to the WISE brown dwarf candidate. Other than this there is
no evidence for any widely separated ( 20 AU) ultra-cool binaries. As an
adjunct to this paper, we make available a source catalog of 7.33
objects detected in all of these Spitzer follow-up fields for use
by the astronomical community. The complete catalog includes the Spitzer 3.6
and 4.5 m photometry, along with positionally matched and
photometry from USNO-B; , , and photometry from 2MASS; and ,
, , and photometry from the WISE all-sky catalog
Spitzer Photometry of WISE-Selected Brown Dwarf and Hyper-Lumninous Infrared Galaxy Candidates
We present Spitzer 3.6 and 4.5 micrometer photometry and positions for a sample of 1510 brown dwarf candidates identified by the Wide-field Infrared Survey Explorer (WISE) all-sky survey. Of these, 166 have been spectroscopically classified as objects with spectral types M(1), L(7), T(146), and Y(12). Sixteen other objects are non-(sub)stellar in nature. The remainder are most likely distant L and T dwarfs lacking spectroscopic verification, other Y dwarf candidates still awaiting follow-up, and assorted other objects whose Spitzer photometry reveals them to be background sources. We present a catalog of Spitzer photometry for all astrophysical sources identified in these fields and use this catalog to identify seven fainter (4.5 m to approximately 17.0 mag) brown dwarf candidates, which are possibly wide-field companions to the original WISE sources. To test this hypothesis, we use a sample of 919 Spitzer observations around WISE-selected high-redshift hyper-luminous infrared galaxy candidates. For this control sample, we find another six brown dwarf candidates, suggesting that the seven companion candidates are not physically associated. In fact, only one of these seven Spitzer brown dwarf candidates has a photometric distance estimate consistent with being a companion to the WISE brown dwarf candidate. Other than this, there is no evidence for any widely separated (greater than 20 AU) ultra-cool binaries. As an adjunct to this paper, we make available a source catalog of 7.33 x 10(exp 5) objects detected in all of these Spitzer follow-up fields for use by the astronomical community. The complete catalog includes the Spitzer 3.6 and 4.5 m photometry, along with positionally matched B and R photometry from USNO-B; J, H, and Ks photometry from Two Micron All-Sky Survey; and W1, W2, W3, and W4 photometry from the WISE all-sky catalog
Clusters of Galaxies in the First Half of the Universe from the IRAC Shallow Survey
We have identified 335 galaxy cluster and group candidates, 106 of which are
at z > 1, using a 4.5 um selected sample of objects from a 7.25 deg^2 region in
the Spitzer Infrared Array Camera (IRAC) Shallow Survey. Clusters were
identified as 3-dimensional overdensities using a wavelet algorithm, based on
photometric redshift probability distributions derived from IRAC and NOAO Deep
Wide-Field Survey data. We estimate only ~10% of the detections are spurious.
To date 12 of the z > 1 candidates have been confirmed spectroscopically, at
redshifts from 1.06 to 1.41. Velocity dispersions of ~750 km/s for two of these
argue for total cluster masses well above 10^14 M_sun, as does the mass
estimated from the rest frame near infrared stellar luminosity. Although not
selected to contain a red sequence, some evidence for red sequences is present
in the spectroscopically confirmed clusters, and brighter galaxies are
systematically redder than the mean galaxy color in clusters at all redshifts.
The mean I - [3.6] color for cluster galaxies up to z ~ 1 is well matched by a
passively evolving model in which stars are formed in a 0.1 Gyr burst starting
at redshift z_f = 3. At z > 1, a wider range of formation histories is needed,
but higher formation redshifts (i.e. z_f > 3) are favored for most clusters.Comment: 56 pages, 19 figures, 3 tables, landscape tables 1 (p. 14) and 2 (p.
29) should be printed separately. Accepted for publication in Astrophysical
Journal, updated version will be posted upon publicatio
LSST Science Book, Version 2.0
A survey that can cover the sky in optical bands over wide fields to faint
magnitudes with a fast cadence will enable many of the exciting science
opportunities of the next decade. The Large Synoptic Survey Telescope (LSST)
will have an effective aperture of 6.7 meters and an imaging camera with field
of view of 9.6 deg^2, and will be devoted to a ten-year imaging survey over
20,000 deg^2 south of +15 deg. Each pointing will be imaged 2000 times with
fifteen second exposures in six broad bands from 0.35 to 1.1 microns, to a
total point-source depth of r~27.5. The LSST Science Book describes the basic
parameters of the LSST hardware, software, and observing plans. The book
discusses educational and outreach opportunities, then goes on to describe a
broad range of science that LSST will revolutionize: mapping the inner and
outer Solar System, stellar populations in the Milky Way and nearby galaxies,
the structure of the Milky Way disk and halo and other objects in the Local
Volume, transient and variable objects both at low and high redshift, and the
properties of normal and active galaxies at low and high redshift. It then
turns to far-field cosmological topics, exploring properties of supernovae to
z~1, strong and weak lensing, the large-scale distribution of galaxies and
baryon oscillations, and how these different probes may be combined to
constrain cosmological models and the physics of dark energy.Comment: 596 pages. Also available at full resolution at
http://www.lsst.org/lsst/sciboo
The CatWISE2020 Catalog
The CatWISE2020 Catalog consists of 1,890,715,640 sources over the entire sky
selected from WISE and NEOWISE survey data at 3.4 and 4.6 m (W1 and W2)
collected from 2010 Jan. 7 to 2018 Dec. 13. This dataset adds two years to that
used for the CatWISE Preliminary Catalog (Eisenhardt et al., 2020), bringing
the total to six times as many exposures spanning over sixteen times as large a
time baseline as the AllWISE catalog. The other major change from the CatWISE
Preliminary Catalog is that the detection list for the CatWISE2020 Catalog was
generated using (Schlafly et al. 2019), while the CatWISE
Preliminary Catalog used the detection software used for AllWISE. These two
factors result in roughly twice as many sources in the CatWISE2020 Catalog. The
scatter with respect to photometry at faint magnitudes in the
COSMOS field, which is out of the Galactic plane and at low ecliptic latitude
(corresponding to lower WISE coverage depth) is similar to that for the CatWISE
Preliminary Catalog. The 90% completeness depth for the CatWISE2020 Catalog is
at W1=17.7 mag and W2=17.5 mag, 1.7 mag deeper than in the CatWISE Preliminary
Catalog. From comparison to , CatWISE2020 motions are accurate at
the 20 mas yr level for W115 mag sources, and at the mas
yr level for W117 mag sources. This level of precision represents
a 12 improvement over AllWISE. The CatWISE catalogs are available in
the WISE/NEOWISE Enhanced and Contributed Products area of the NASA/IPAC
Infrared Science Archive.Comment: 27 pages, 24 figure, 2 tables. Accepted for publication in ApJS.
arXiv admin note: text overlap with arXiv:1908.0890
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