81 research outputs found
Molecular Gas in the z=1.2 Ultraluminous Merger GOODS J123634.53+621241.3
We report the detection of CO(2-1) emission from the z=1.2 ultraluminous
infrared galaxy (ULIRG) GOODS J123634.53+621241.3 (also known as the
sub-millimeter galaxy GN26). These observations represent the first discovery
of high-redshift CO emission using the new Combined Array for Research in
Millimeter-Wave Astronomy (CARMA). Of all high-redshift (z>1) galaxies within
the GOODS-North field, this source has the largest far-infrared (FIR) flux
observed in the Spitzer 70um and 160um bands. The CO redshift confirms the
optical identification of the source, and the bright CO(2-1) line suggests the
presence of a large molecular gas reservoir of about 7x10^10 M(sun). The
infrared-to-CO luminosity ratio of L(IR)/L'(CO) = 80+/-30 L(sun) (K Km/s
pc^2)^-1 is slightly smaller than the average ratio found in local ULIRGs and
high-redshift sub-millimeter galaxies. The short star-formation time scale of
about 70 Myr is consistent with a starburst associated with the merger event
and is much shorter than the time scales for spiral galaxies and estimates made
for high-redshift galaxies selected on the basis of their B-z and z-K colors.Comment: Accepted for publication in ApJ Letter
SUPPLY CHAIN INTEGRATION IN THE FOOD AND CONSUMER GOODS INDUSTRIES
The interorganizational structures necessary to implement and achieve the logistical performance improvements identified in the Efficient Consumer Response (ECR) initiative and related supply chain management concepts are difficult to develop. Firms continue to struggle to implement integrated programs and techniques, particularly with respect to changing operating structures, relationships, and mindsets to facilitate true supply chain integration. This research explores the logistical strategies and structures used by selected food and consumer goods firms to integrate their supply chains. It illustrates effective integration strategies and identifies critical success factors and barriers to successful ECR implementation. A framework is used to guide managers in developing the competencies essential to integrating the supply chain and to establishing the relationships necessary to operate in an ECR environment. The framework, entitled Supply Chain 2000, depicts supply chain value creation as achieving synchronization and coordination across four critical supply chain flows: product/service; market accommodation; information; and cash.Industrial Organization,
A merger in the dusty, galaxy A1689-zD1?
The gravitationally-lensed galaxy A1689-zD1 is one of the most distant
spectroscopically confirmed sources (). It is the earliest known galaxy
where the interstellar medium (ISM) has been detected; dust emission was
detected with the Atacama Large Millimetre Array (ALMA). A1689-zD1 is also
unusual among high-redshift dust emitters as it is a sub-L* galaxy and is
therefore a good prospect for the detection of gaseous ISM in a more typical
galaxy at this redshift. We observed A1689-zD1 with ALMA in bands 6 and 7 and
with the Green Bank Telescope (GBT) in band . To study the structure of
A1689-zD1, we map the mm thermal dust emission and find two spatial components
with sizes about \,kpc (lensing-corrected). The rough spatial
morphology is similar to what is observed in the near-infrared with {\it HST}
and points to a perturbed dynamical state, perhaps indicative of a major merger
or a disc in early formation. The ALMA photometry is used to constrain the
far-infrared spectral energy distribution, yielding a dust temperature (--\,K for ). We do not detect the CO(3-2) line
in the GBT data with a 95\% upper limit of 0.3\,mJy observed. We find a slight
excess emission in ALMA band~6 at 220.9\,GHz. If this excess is real, it is
likely due to emission from the [CII] 158.8\,m line at . The stringent upper limits on the [CII]/ luminosity ratio
suggest a [CII] deficit similar to several bright quasars and massive
starbursts.Comment: 9 pages, accepted to MNRAS, in pres
The Infrared Properties of Submillimeter Galaxies: Clues From Ultra-Deep 70 Micron Imaging
We present 70 micron properties of submillimeter galaxies (SMGs) in the Great
Observatories Origins Deep Survey (GOODS) North field. Out of thirty
submillimeter galaxies (S_850 > 2 mJy) in the central GOODS-N region, we find
two with secure 70 micron detections. These are the first 70 micron detections
of SMGs. One of the matched SMGs is at z ~ 0.5 and has S_70/S_850 and S_70/S_24
ratios consistent with a cool galaxy. The second SMG (z = 1.2) has
infrared-submm colors which indicate it is more actively forming stars. We
examine the average 70 micron properties of the SMGs by performing a stacking
analysis, which also allows us to estimate that S_850 > 2 mJy SMGs contribute 9
+- 3% of the 70 micron background light. The S_850/S_70 colors of the SMG
population as a whole is best fit by cool galaxies, and because of the
redshifting effects these constraints are mainly on the lower z sub-sample. We
fit Spectral Energy Distributions (SEDs) to the far-infrared data points of the
two detected SMGs and the average low redshift SMG (z_{median}= 1.4). We find
that the average low-z SMG has a cooler dust temperature than local
ultraluminous infrared galaxies (ULIRGs) of similar luminosity and an SED which
is best fit by scaled up versions of normal spiral galaxies. The average low-z
SMG is found to have a typical dust temperature T = 21 -- 33 K and infrared
luminosity L_{8-1000 micron} = 8.0 \times 10^11 L_sun. We estimate the AGN
contribution to the total infrared luminosity of low-z SMGs is less than 23%.Comment: Accepted by ApJ. 14 pages, 6 figures. Minor revisions 20th Dec 200
Spitzer Mid-Infrared Spectroscopy of Infrared Luminous Galaxies at z~2 III: Far-IR to Radio Properties and Optical Spectral Diagnostics
We present the far-IR, millimeter, and radio photometry as well as optical
and near-IR spectroscopy of a sample of 48 z~1-3 Spitzer-selected ULIRGs with
IRS mid-IR spectra. Our goals are to compute their bolometric emission, and to
determine both the presence and relative strength of their AGN and starburst
components. We find that strong-PAH sources tend to have higher 160um and 1.2mm
fluxes than weak-PAH sources. The depth of the 9.7um silicate feature does not
affect MAMBO detectability. We fit the far-IR SEDs of our sample and find an
average ~7x10^{12}Lsun for our z>1.5 sources. Spectral decomposition
suggests that strong-PAH sources typically have ~20-30% AGN fractions. Weak-PAH
sources by contrast tend to have >~70% AGN fractions, with a few sources having
comparable contributions of AGN and starbursts. The optical line diagnostics
support the presence of AGN in the bulk of the weak-PAH sources. With one
exception, our sources are narrow-line sources, show no obvious correspondence
between the optical extinction and the silicate feature depth, and, in two
cases, show evidence for outflows. Radio AGN are present in both strong-PAH and
weak-PAH sources. This is supported by our sample's far-IR-to-radio ratios (q)
being consistently below the average value of 2.34 for local star-forming
galaxies. We use survival analysis to include the lower-limits given by the
radio-undetected sources, arriving at =2.07+/-0.01 for our z>1.5 sample. In
total, radio and, where available, optical line diagnostics support the
presence of AGN in 57% of the z>1.5 sources, independent of IR-based
diagnostics. For higher-z sources, the AGN luminosities alone are estimated to
be >10^{12}Lsun, which, supported by the [OIII] luminosities, implies that the
bulk of our sources host obscured quasars.Comment: 22 pages, 14 figures, accepted for publication in Ap
Multiwavelength Observations of the Low Metallicity Blue Compact Dwarf Galaxy SBS 0335-052
New infrared and millimeter observations from Keck, Palomar, ISO, and OVRO
and archival data from the NRAO VLA and IRAS are presented for the low
metallicity blue compact dwarf galaxy SBS 0335-052. Mid-infrared imaging shows
this young star-forming system is compact (0.31"; 80 pc) at 12.5 microns. The
large Br-gamma equivalent width (235 Angstroms) measured from integral field
spectroscopy is indicative of a ~5 Myr starburst. The central source appears to
be optically thin in emission, containing both a warm (~80 K) and a hot (~210
K) dust component, and the overall interstellar radiation field is quite
intense, about 10,000 times the intensity in the solar neighborhood. CO
emission is not detected, though the galaxy shows an extremely high global H I
gas-to-dust mass ratio, high even for blue compact dwarfs. Finally, the
galaxy's mid-infrared-to-optical and mid-to-near-infrared luminosity ratios are
quite high, whereas its far-infrared-to-radio and far-infrared-to-optical flux
ratios are surprisingly similar to what is seen in normal star-forming
galaxies. The relatively high bolometric infrared-to-radio ratio is more easily
understood in the context of such a young system with negligible nonthermal
radio continuum emission. These new lines of evidence may outline features
common to primordial galaxies found at high redshift.Comment: 28 pages including 6 figures; accepted for publication in the
Astronomical Journa
Galaxy Clustering in Far-Infrared SWIRE Fields
We present measurements of galaxy clustering detected in the six
SWIRE fields in all MIPS channels at 24, 70, and 160 microns. The measurements
include the low-order 2-point angular correlation functions, and high-order
probes including probability distribution functions and Rényi information
Tracing PAHs and Warm Dust Emission in the Seyfert Galaxy NGC 1068
We present a study of the nearby Seyfert galaxy NGC 1068 using mid- and far-
infrared data acquired with the IRAC, IRS, and MIPS instruments aboard the
Spitzer Space Telescope. The images show extensive 8 um and 24 um emission
coinciding with star formation in the inner spiral approximately 15" (1 kpc)
from the nucleus, and a bright complex of star formation 47" (3 kpc) SW of the
nucleus. The brightest 8 um PAH emission regions coincide remarkably well with
knots observed in an Halpha image. Strong PAH features at 6.2, 7.7, 8.6, and
11.3 um are detected in IRS spectra measured at numerous locations inside,
within, and outside the inner spiral. The IRAC colors and IRS spectra of these
regions rule out dust heated by the AGN as the primary emission source; the
SEDs are dominated by starlight and PAH emission. The equivalent widths and
flux ratios of the PAH features in the inner spiral are generally consistent
with conditions in a typical spiral galaxy ISM. Interior to the inner spiral,
the influence of the AGN on the ISM is evident via PAH flux ratios indicative
of a higher ionization parameter and a significantly smaller mean equivalent
width than observed in the inner spiral. The brightest 8 and 24 um emission
peaks in the disk of the galaxy, even at distances beyond the inner spiral, are
located within the ionization cones traced by [O III]/Hbeta, and they are also
remarkably well aligned with the axis of the radio jets. Although it is
possible that radiation from the AGN may directly enhance PAH excitation or
trigger the formation of OB stars that subsequently excite PAH emission at
these locations in the inner spiral, the orientation of collimated radiation
from the AGN and star formation knots in the inner spiral could be
coincidental. (abridged)Comment: 20 pages, 11 figures; AJ, accepted; full resolution version available
at http://spider.ipac.caltech.edu/staff/jhhowell/astro/howelln1068.pd
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