189 research outputs found
First mid-infrared spectrum of a faint high-z galaxy: Observations of CFRS 14.1157 with the Infrared Spectrograph on the Spitzer Space Telescope
The unprecedented sensitivity of the Infrared Spectrograph on the Spitzer
Space Telescope allows for the first time the measurement of mid-infrared
spectra from 14 to 38 microns of faint high-z galaxies. This unique capability
is demonstrated with observations of sources having 16 micron fluxes of 3.6 mJy
(CFRS 14.1157) and 0.35 mJy (CFRS 14.9025). A spectral-fitting technique is
illustrated which determines the redshift by fitting emission and absorption
features characteristic of nearby galaxies to the spectrum of an unknown
source. For CFRS 14.1157, the measured redshift is z = 1.00+/-0.20 in agreement
with the published result of z = 1.15. The spectrum is dominated by emission
from an AGN, similar to the nucleus of NGC 1068, rather than a typical
starburst with strong PAH emission like M82. Such spectra will be crucial in
characterizing the nature of newly discovered distant galaxies, which are too
faint for optical follow-up.Comment: Accepted in ApJ Sup. Spitzer Special Issue, 4 pages, 5 figure
Spectroscopic Redshifts to z > 2 for Optically Obscured Sources Discovered with the Spitzer Space Telescope
We have surveyed a field covering 9.0 degrees^2 within the NOAO Deep
Wide-Field Survey region in Bootes with the Multiband Imaging Photometer on the
Spitzer Space Telescope (SST) to a limiting 24 um flux density of 0.3 mJy.
Thirty one sources from this survey with F(24um) > 0.75 mJy which are optically
very faint (R > 24.5 mag) have been observed with the low-resolution modules of
the Infrared Spectrograph on SST. Redshifts derived primarily from strong
silicate absorption features are reported here for 17 of these sources; 10 of
these are optically invisible (R > 26 mag), with no counterpart in B_W, R, or
I. The observed redshifts for 16 sources are 1.7 < z < 2.8. These represent a
newly discovered population of highly obscured sources at high redshift with
extreme infrared to optical ratios. Using IRS spectra of local galaxies as
templates, we find that a majority of the sources have mid-infrared spectral
shapes most similar to ultraluminous infrared galaxies powered primarily by
AGN. Assuming the same templates also apply at longer wavelengths, bolometric
luminosities exceed 10^13 L(solar).Comment: Accepted for publication on 7 Feb 2005 in ApJL. 7 pages 2 figure
Spitzer-IRS Spectroscopy of the Prototypical Starburst Galaxy NGC7714
We present observations of the starburst galaxy NGC 7714 with the Infrared
Spectrograph IRS on board the Spitzer Space Telescope. The spectra yield a
wealth of ionic and molecular features that allow a detailed characterization
of its properties. NGC 7714 has an HII region-like spectrum with strong PAH
emission features. We find no evidence for an obscured active galactic nucleus,
and with [NeIII]/[NeII]~0.73, NGC7714 lies near the upper end of
normal-metallicity starburst galaxies. With very little slicate absorption and
a temperature of the hottest dust component of 340K, NGC 7714 is the perfect
template for a young, unobscured starburstComment: To appear in the special ApJSS issue on early results from Spitze
CCAT-prime: Science with an Ultra-widefield Submillimeter Observatory at Cerro Chajnantor
We present the detailed science case, and brief descriptions of the telescope
design, site, and first light instrument plans for a new ultra-wide field
submillimeter observatory, CCAT-prime, that we are constructing at a 5600 m
elevation site on Cerro Chajnantor in northern Chile. Our science goals are to
study star and galaxy formation from the epoch of reionization to the present,
investigate the growth of structure in the Universe, improve the precision of
B-mode CMB measurements, and investigate the interstellar medium and star
formation in the Galaxy and nearby galaxies through spectroscopic,
polarimetric, and broadband surveys at wavelengths from 200 um to 2 mm. These
goals are realized with our two first light instruments, a large field-of-view
(FoV) bolometer-based imager called Prime-Cam (that has both camera and an
imaging spectrometer modules), and a multi-beam submillimeter heterodyne
spectrometer, CHAI. CCAT-prime will have very high surface accuracy and very
low system emissivity, so that combined with its wide FoV at the unsurpassed
CCAT site our telescope/instrumentation combination is ideally suited to pursue
this science. The CCAT-prime telescope is being designed and built by Vertex
Antennentechnik GmbH. We expect to achieve first light in the spring of 2021.Comment: Presented at SPIE Millimeter, Submillimeter, and Far-Infrared
Detectors and Instrumentation for Astronomy IX, June 14th, 201
Maternal iron kinetics and maternalâfetal iron transfer in normal-weight and overweight pregnancy
Background
Inflammation during pregnancy may aggravate iron deficiency (ID) by increasing serum hepcidin and reducing iron absorption. This could restrict iron transfer to the fetus, increasing risk of infant ID and its adverse effects.
Objectives
We aimed to assess whether iron bioavailability and/or iron transfer to the fetus is impaired in overweight/obese (OW) pregnant women with adiposity-related inflammation, compared with normal-weight (NW) pregnant women.
Methods
In this prospective study, we followed NW (n = 43) and OW (n = 40) pregnant women who were receiving iron supplements from the 14th week of gestation to term and followed their infants to age 6 mo. We administered 57Fe and 58Fe in test meals mid-second and mid-third trimester, and measured tracer kinetics throughout pregnancy and infancy.
Results
In total, 38 NW and 36 OW women completed the study to pregnancy week 36, whereas 30 NW and 27 OW motherâinfant pairs completed the study to 6 mo postpartum. Both groups had comparable iron status, hemoglobin, and serum hepcidin throughout pregnancy. Compared with the NW, the OW pregnant women had 1) 43% lower fractional iron absorption (FIA) in the third trimester (P = 0.033) with median [IQR] FIA of 23.9% [11.4%â35.7%] and 13.5% [10.8%â19.5%], respectively; and 2) 17% lower maternalâfetal iron transfer from the first tracer (P = 0.051) with median [IQR] maternalâfetal iron transfer of 4.8% [4.2%â5.4%] and 4.0% [3.6%â4.6%], respectively. Compared with the infants born to NW women, infants born to OW women had lower body iron stores (BIS) with median [IQR] 7.7 [6.3â8.8] and 6.6 [4.6â9.2] mg/kg body weight at age 6 mo, respectively (P = 0.024). Prepregnancy BMI was a negative predictor of maternalâfetal iron transfer (ÎČ = â0.339, SE = 0.144, P = 0.025) and infant BIS (ÎČ = â0.237, SE = 0.026, P = 0.001).
Conclusions
Compared with NW, OW pregnant women failed to upregulate iron absorption in late pregnancy, transferred less iron to their fetus, and their infants had lower BIS. These impairments were associated with inflammation independently of serum hepcidin
Observations of Ultraluminous Infrared Galaxies with the Infrared Spectrograph on the Spitzer Space Telescope: Early Results on Mrk 1014, Mrk 463, and UGC 5101
We present spectra taken with the Infrared Spectrograph on Spitzer covering
the 5-38micron region of three Ultraluminous Infrared Galaxies (ULIRGs): Mrk
1014 (z=0.163), and Mrk 463 (z=0.051), and UGC 5101 (z=0.039). The continua of
UGC 5101 and Mrk 463 show strong silicate absorption suggesting significant
optical depths to the nuclei at 10microns. UGC 5101 also shows the clear
presence of water ice in absorption. PAH emission features are seen in both Mrk
1014 and UGC 5101, including the 16.4micron line in UGC 5101. The fine
structure lines are consistent with dominant AGN power sources in both Mrk 1014
and Mrk 463. In UGC 5101 we detect the [NeV] 14.3micron emission line providing
the first direct evidence for a buried AGN in the mid-infrared. The detection
of the 9.66micron and 17.03micron H emission lines in both UGC 5101 and
Mrk 463 suggest that the warm molecular gas accounts for 22% and 48% of the
total molecular gas masses in these galaxies.Comment: Accepted in ApJ Sup. Spitzer Special Issue, 4 pages, 3 figure
The Infrared Spectrograph on the Spitzer Space Telescope
The Infrared Spectrograph (IRS) is one of three science instruments on the
Spitzer Space Telescope. The IRS comprises four separate spectrograph modules
covering the wavelength range from 5.3 to 38micron with spectral resolutions, R
\~90 and 600, and it was optimized to take full advantage of the very low
background in the space environment. The IRS is performing at or better than
the pre-launch predictions. An autonomous target acquisition capability enables
the IRS to locate the mid-infrared centroid of a source, providing the
information so that the spacecraft can accurately offset that centroid to a
selected slit. This feature is particularly useful when taking spectra of
sources with poorly known coordinates. An automated data reduction pipeline has
been developed at the Spitzer Science Center.Comment: Accepted in ApJ Sup. Spitzer Special Issue, 6 pages, 4 figure
Spitzer/IRS Observations of the Redshift 3.91 quasar APM 08279+5255
The Infrared Spectrograph (IRS) onboard the Spitzer Space Telescope (SST) has
been used to obtain low and moderate resolution spectra of the dust and
gas-rich quasar APM08279+5255 (z=3.91). Broad Paschen and
recombination lines of hydrogen were detected at wavelengths of 9.235 and
6.315microns, as well as a strong, red continuum that is a smooth power law
over the observed (rest frame) wavelength range 5.3-35microns (1.08 -
7.1microns). The observed P/P line flux ratio of 1.050.2 is
far from the case B value of ~2 and simple models of high density, high optical
depth ionized gas regions (~1.8). This deviation is opposite in sense to the
expected effect of reddening. No evidence is found in the spectrum for either
the 3.3micron or 6.2micron emission features usually attributed to aromatic
hydrocarbons in gas rich galaxies in the local Universe. This is consistent
with the high luminosity AGN nature of APM08279+5255.Comment: Accepted in ApJ Sup. Spitzer Special Issue, 4 pages, 1 figur
Imaging of High Redshift Submillimeter Galaxies at 16 and 22microns with the Spitzer/IRS: Revealing a population at z>2.5
We present broad band imaging observations obtained with the ``peak up''
imagers of the Spitzer Space Telescope Infrared Spectrograph (IRS) at
wavelengths of 16micron and 22micron for a number of sources detected primarily
at submillimeter wavelengths, which are believed to be at high, though
undetermined, redshift. We targeted 11 sources originally detected by SCUBA and
5 submillimeter sources detected at 1.2mm by MAMBO. Two optically discovered
quasars with z>6 were also observed to determine if there is detectable dust
emission at such high redshifts. Seven of the submillimeter sources and both
high-redshift quasars were detected, and upper limits of about ~50microJy apply
to the remainder. Using their mid-/far-IR colors, we demonstrate that all of
the submillimeter sources are at z>1.4. The mid-IR colors for two of our
detections and three of our strong upper limits suggest that these galaxies
must be at z>2.5. We also introduce a technique for estimating redshifts and
source characteristics based only on the ratio of fluxes in the 16micron and
22micron images.Comment: Accepted in ApJ Sup. Spitzer Special Issue, 4 pages, 1 figur
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