146 research outputs found
The molecular gas content of z > 6.5 Lyman-alpha emitters
We present results from a sensitive search for CO J=1-0 line emission in two
z> 6.5 Lyman-alpha emitters (LAEs) with the Green Bank Telescope. CO J=1-0
emission was not detected from either object. For HCM 6A, at z ~ 6.56, the
lensing magnification factor of ~4.5 implies that the CO non-detection yields
stringent constraints on the CO J=1-0 line luminosity and molecular gas mass of
the LAE, L'(CO) < 6.1x10^9 x (dV/300)^(1/2) K km/s pc^2 and M(H_2) < 4.9x10^9 x
(dV/300)^(1/2) x (X(CO)/0.8) Msun. These are the strongest limits obtained so
far for a z >~ 6 galaxy. For IOK-1, the constraints are somewhat less
sensitive, L'(CO) < 2.3x10^10 x (dV/300)^(1/2) K km/s pc^2 and M(H_2) <
1.9x10^10 x (dV/300)^(1/2) x (X(CO)/0.8) Msun. The non-detection of CO J=1-0
emission in HCM~6A, whose high estimated star formation rate, dust extinction,
and lensing magnification make it one of the best high-z LAEs for such a
search, implies that typical z >~ 6 LAEs are likely to have significantly lower
CO line luminosities than massive sub-mm galaxies and hyperluminous infrared
quasars at similar redshifts, due to either a significantly lower molecular gas
content or a higher CO-to-H_2 conversion factor.Comment: Accepted for publication in ApJ Letter
Infrared Emission from the Nearby Cool Core Cluster Abell 2597
We observed the brightest central galaxy (BCG) in the nearby (z=0.0821) cool
core galaxy cluster Abell 2597 with the IRAC and MIPS instruments on board the
Spitzer Space Telescope. The BCG was clearly detected in all Spitzer
bandpasses, including the 70 and 160 micron wavebands. We report aperture
photometry of the BCG. The spectral energy distribution exhibits a clear excess
in the FIR over a Rayleigh-Jeans stellar tail, indicating a star formation rate
of ~4-5 solar masses per year, consistent with the estimates from the UV and
its H-alpha luminosity. This large FIR luminosity is consistent with that of a
starburst or a Luminous Infrared Galaxy (LIRG), but together with a very
massive and old population of stars that dominate the energy output of the
galaxy. If the dust is at one temperature, the ratio of 70 to 160 micron fluxes
indicate that the dust emitting mid-IR in this source is somewhat hotter than
the dust emitting mid-IR in two BCGs at higher-redshift (z~0.2-0.3) and higher
FIR luminosities observed earlier by Spitzer, in clusters Abell 1835 and Zwicky
3146.Comment: Accepted at Ap
Exploring the NRO Opportunity for a Hubble-sized Wide-field Near-IR Space Telescope -- NEW WFIRST
We discuss scientific, technical and programmatic issues related to the use
of an NRO 2.4m telescope for the WFIRST initiative of the 2010 Decadal Survey.
We show that this implementation of WFIRST, which we call "NEW WFIRST," would
achieve the goals of the NWNH Decadal Survey for the WFIRST core programs of
Dark Energy and Microlensing Planet Finding, with the crucial benefit of deeper
and/or wider near-IR surveys for GO science and a potentially Hubble-like Guest
Observer program. NEW WFIRST could also include a coronagraphic imager for
direct detection of dust disks and planets around neighboring stars, a
high-priority science and technology precursor for future ambitious programs to
image Earth-like planets around neighboring stars.Comment: 76 pages, 26 figures -- associated with the Princeton "New Telescope
Meeting
Modulation of outer bank erosion by slump blocks: disentangling the protective and destructive role of failed material on the three-dimensional flow structure
The three-dimensional flow field near the banks of alluvial channels is the primary factor controlling rates of bank erosion. Although submerged slump blocks and associated large-scale bank roughness elements have both previously been proposed to divert flow away from the bank, direct observations of the interaction between eroded bank material and the 3-D flow field are lacking. Here we use observations from multibeam echo sounding, terrestrial laser scanning, and acoustic Doppler current profiling to quantify, for the first time, the influence of submerged slump blocks on the near-bank flow field. In contrast to previous research emphasizing their influence on flow diversion away from the bank, we show that slump blocks may also deflect flow onto the bank, thereby increasing local shear stresses and rates of erosion. We use our measurements to propose a conceptual model for how submerged slump blocks interact with the flow field to modulate bank erosion
Cooperativity between the preproinsulin mRNA untranslated regions Is necessary for glucose-stimulated translation
Glucose regulates proinsulin biosynthesis via stimulation of the translation of the preproinsulin mRNA in pancreatic β-cells. However, the mechanism by which this occurs has remained unclear. Using recombinant adenoviruses that express the preproinsulin mRNA with defined alterations, the untranslated regions (UTRs) of the preproinsulin mRNA were examined for elements that specifically control translation of the mRNA in rat pancreatic islets. These studies revealed that the preproinsulin 5′-UTR was necessary for glucose stimulation of preproinsulin mRNA translation, whereas the 3′-UTR appeared to suppress translation. However, together the 5′- and 3′-UTRs acted cooperatively to markedly increase glucose-induced proinsulin biosynthesis. In primary hepatocytes the presence of the preproinsulin 3′-UTR led to reduced mRNA levels compared with the presence of the SV40 3′-UTR, consistent with the presence of mRNA stability determinants in the 3′-UTR that stabilize the preproinsulin mRNA in a pancreatic β-cell-specific manner. Translation of these mRNAs in primary hepatocytes was not stimulated by glucose, indicating that regulated translation of the preproinsulin mRNA occurs in a pancreatic β-cell-specific manner. Thus, the untranslated regions of the preproinsulin mRNA play crucial roles in regulating insulin production and therefore glucose homeostasis by regulating the translation and the stability of the preproinsulin mRNA
A proposal to exploit galaxy-21cm synergies to shed light on the Epoch of Reionization
This white paper outlines the benefits of synergizing WFIRST, Subaru Hyper Suprime-Cam or other >25m-class telescopes galaxy observations with SKA 21cm measurements to constrain the nature of reionization (ionization history and topology) and its sources. <p/
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