6,927 research outputs found
Spitzer Warm Mission Workshop Introduction
The Spitzer Warm Mission Workshop was held June 4–5, 2007, to explore the science drivers for the warm Spitzer mission and help the Spitzer Science Center develop a new science operations philosophy. We must continue to maximize the science return with the reduced resources available, both using (a) the shortest two IRAC channels, and (b) archival research with the rich Spitzer archive. This paper summarizes the overview slides presented to the workshop participant
Microlens Parallax Measurements with a Warm Spitzer
Because Spitzer is an Earth-trailing orbit, losing about 0.1 AU/yr, it is
excellently located to perform microlens parallax observations toward the
Magellanic Clouds (LMC/SMC) and the Galactic bulge. These yield the so-called
``projected velocity'' of the lens, which can distinguish statistically among
different populations. A few such measurements toward the LMC/SMC would reveal
the nature of the lenses being detected in this direction (dark halo objects,
or ordinary LMC/SMC stars). Cool Spitzer has already made one such measurement
of a (rare) bright red-clump source, but warm (presumably less oversubscribed)
Spitzer could devote the extra time required to obtain microlens parallaxes for
the more common, but fainter, turnoff sources. Warm Spitzer could observe bulge
microlenses for 38 days per year, which would permit up to 24 microlens
parallaxes per year. This would yield interesting information on the disk mass
function, particularly old brown dwarfs, which at present are inaccessible by
other techniques. Target-of-Opportunity (TOO) observations should be divided
into RTOO/DTOO, i.e., ``regular'' and ``disruptive'' TOOs, as pioneered by the
Space Interferometry Mission (SIM). LMC/SMC parallax measurements would be
DTOO, but bulge measurements would be RTOO, i.e., they could be scheduled in
advance, without knowing exactly which star was to be observed.Comment: 6 pages + 1 Figure, To be presented at The Warm Spitzer Mission
Workshop, 4-5 June 2007, Pasaden
HP2 survey: III The California Molecular Cloud--A Sleeping Giant Revisited
We present new high resolution and dynamic range dust column density and
temperature maps of the California Molecular Cloud derived from a combination
of Planck and Herschel dust-emission maps, and 2MASS NIR dust-extinction maps.
We used these data to determine the ratio of the 2.2 micron extinction
coefficient to the 850 micron opacity and found the value to be close to that
found in similar studies of the Orion B and Perseus clouds but higher than that
characterizing the Orion A cloud, indicating that variations in the fundamental
optical properties of dust may exist between local clouds. We show that over a
wide range of extinction, the column density probability distribution function
(PDF) of the cloud can be well described by a simple power law with an
index that represents a steeper decline with column density than found in
similar studies of the Orion and Perseus clouds. Using only the protostellar
population of the cloud and our extinction maps we investigate the Schmidt
relation within the cloud. We show that the protostellar surface density,
, is directly proportional to the ratio of the protostellar and cloud
pdfs. We use the cumulative distribution of protostars to infer the functional
forms for both and PDF. We find that is best
described by two power-law functions with steeper indicies than found in other
local GMCs. We find that the protostellar pdf is a declining function of
extinction also best described by two power-laws whose behavior mirrors that of
. Our observations suggest that variations both in the slope of the
Schmidt relation and in the sizes of the protostellar populations between GMCs
are largely driven by variations in the slope of the cloud pdf. This confirms
earlier studies suggesting that cloud structure plays a major role in setting
the global star formation rates in GMCs.Comment: Accepted for publication in Astronomy and Astrophysics. Corrected
typos in source coordinates in table A.
NICMOS Snapshot Survey of Damped Lyman Alpha Quasars
We image 19 quasars with 22 damped Lyman alpha (DLA) systems using the F160W
filter and the Near-Infrared Camera and Multiobject Spectrograph aboard the
Hubble Space Telescope, in both direct and coronagraphic modes. We reach 5
sigma detection limits of ~H=22 in the majority of our images. We compare our
observations to the observed Lyman-break population of high-redshift galaxies,
as well as Bruzual & Charlot evolutionary models of present-day galaxies
redshifted to the distances of the absorption systems. We predict H magnitudes
for our DLAs, assuming they are producing stars like an L* Lyman-break galaxy
(LBG) at their redshift. Comparing these predictions to our sensitivity, we
find that we should be able to detect a galaxy around 0.5-1.0 L* (LBG) for most
of our observations. We find only one new possible candidate, that near
LBQS0010-0012. This scarcity of candidates leads us to the conclusion that most
DLA systems are not drawn from a normal LBG luminosity function nor a local
galaxy luminosity function placed at these high redshifts.Comment: 31 pages, 8 figures, Accepted for Feb. 10 issue of Ap
HST/ACS weak lensing analysis of the galaxy cluster RDCS 1252.9-2927 at z=1.24
We present a weak lensing analysis of one of the most distant massive galaxy
cluster known, RDCS 1252.9-2927 at z=1.24, using deep images from the Advanced
Camera for Survey (ACS) on board the Hubble Space Telescope (HST). By taking
advantage of the depth and of the angular resolution of the ACS images, we
detect for the first time at z>1 a clear weak lensing signal in both the i
(F775W) and z (F850LP) filters. We measure a 5-\sigma signal in the i band and
a 3-\sigma signal in the shallower z band image. The two radial mass profiles
are found to be in very good agreement with each other, and provide a
measurement of the total mass of the cluster inside a 1Mpc radius of M(<1Mpc) =
(8.0 +/- 1.3) x 10^14 M_\odot in the current cosmological concordance model h
=0.70, \Omega_m=0.3, \Omega_\Lambda=0.7, assuming a redshift distribution of
background galaxies as inferred from the Hubble Deep Fields surveys. A weak
lensing signal is detected out to the boundary of our field (3' radius,
corresponding to 1.5Mpc at the cluster redshift). We detect a small offset
between the centroid of the weak lensing mass map and the brightest cluster
galaxy, and we discuss the possible origin of this discrepancy. The cumulative
weak lensing radial mass profile is found to be in good agreement with the
X-ray mass estimate based on Chandr and XMM-Newton observations, at least out
to R_500=0.5Mpc.Comment: 38 pages, ApJ in press. Full resolution images available at
http://www.eso.org/~prosati/RDCS1252/Lombardi_etal_accepted.pd
Enhancement of the immunoregulatory potency of mesenchymal stromal cells by treatment with immunosuppressive drugs
Background aims Multipotent mesenchymal stromal cells (MSCs) are distinguished by their ability to differentiate into a number of stromal derivatives of interest for regenerative medicine, but they also have immunoregulatory properties that are being tested in a number of clinical settings. Methods We show that brief incubations with rapamycin, everolimus, FK506 or cyclosporine A increase the immunosuppressive potency of MSCs and other cell types. Results The treated MSCs are up to 5-fold more potent at inhibiting the induced proliferation of T lymphocytes in vitro. We show that this effect probably is due to adsorption of the drug by the MSCs during pre-treatment, with subsequent diffusion into co-cultures at concentrations sufficient to inhibit T-cell proliferation. MSCs contain measurable amounts of rapamycin after a 15-min exposure, and the potentiating effect is blocked by a neutralizing antibody to the drug. With the use of a pre-clinical model of acute graft-versus-host disease, we demonstrate that a low dose of rapamycin-treated but not untreated umbilical cord–derived MSCs significantly inhibit the onset of disease. Conclusions The use of treated MSCs may achieve clinical end points not reached with untreated MSCs and allow for infusion of fewer cells to reduce costs and minimize potential side effects
Near-infrared thermal emissivity from ground based atmospheric dust measurements at ORM
We present an analysis of the atmospheric content of aerosols measured at
Observatorio del Roque de los Muchachos (ORM; Canary Islands). Using a laser
diode particle counter located at the Telescopio Nazionale Galileo (TNG) we
have detected particles of 0.3, 0.5, 1.0, 3.0, 5.0 and 10.0 um size. The
seasonal behavior of the dust content in the atmosphere is calculated. The
Spring has been found to be dustier than the Summer, but dusty conditions may
also occur in Winter. A method to estimate the contribution of the aerosols
emissivity to the sky brightness in the near-infrared (NIR) is presented. The
contribution of dust emission to the sky background in the NIR has been found
to be negligible comparable to the airglow, with a maximum contribution of
about 8-10% in the Ks band in the dusty days.Comment: 6 pages, 3 figures, 6 tables, accepted for publication in MNRA
Extremely Red Objects from the NICMOS/HST Parallel Imaging Survey
We present a catalog of extremely red objects discovered using the NICMOS/HST
parallel imaging database and ground-based optical follow-up observations.
Within an area of 16 square arc-minutes, we detect 15 objects with and . We have also obtained K-band photometry for
a subset of the 15 EROs. All of the selected EROs imaged at
K-band have . Our objects have colors in the
range of 1.3 - 2.1, redder than the cluster ellipticals at and
nearly 1 magnitude redder than the average population selected from the F160W
images at the same depth. In addition, among only 22 NICMOS pointings, we
detected two groups or clusters in two fields, each contains 3 or more EROs,
suggesting that extremely red galaxies may be strongly clustered. At bright
magnitudes with , the ERO surface density is similar to what
has been measured by other surveys. At the limit of our sample, F160W = 21.5,
our measured surface density is 0.94 arcmin^{-2}. Excluding the two
possible groups/clusters and the one apparently stellar object, reduces the
surface density to 0.38 arcmin^{-2}.Comment: To appear in the AJ August issue. Replaced with the published versio
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