238 research outputs found
Development of super broadband interferometer in FIR
We are developing the super broad band interferometer by applying the Fourier
Transform Spectrometer(FTS) to aperture synthesis system in mm and sub-mm
bands. We have constructed a compact system based on the Martin and Puplett
type Fourier Transform spectrometer (MP-FT). We call this equipment
Multi-Fourier Transform interferometer (MuFT). The band width of the system can
be extended as large as one wants contrary to the severely limited band width
of the usual interferometer due to the speed of the AD converter. The direct
detectors, e.g. bolometer, SIS video detector, can be used as the focal plane
detectors. This type of detectors have a great advantage in FIR band since they
are free from the quantum limit of the noise which limits the sensitivity of
the heterodyne detectors used in the usual interferometers. Further, the direct
detectors are able to make a large format array contrary to the heterodyne
detectors for which construction of a large format array is practically
difficult. These three characteristics make one be possible to develop high
sensitive super broad band FIR interferometer with wide field of view. In the
laboratory experiments, we have succeeded in measuring the spectroscopically
resolved 2D image of the source in 150GHz-900GHz band. The future application
of this technique to the observations from the space could open new interesting
possibilities in FIR astronomy.Comment: 9 pages, presented at the Glasgow SPIE conference "Optical, Infrared,
and Millimeter Space Telescopes", to appear in Proc. SPIE, vol. #5487-20
Very compact millimeter sizes for composite star-forming/AGN submillimeter galaxies
We report the study of far-IR sizes of submillimeter galaxies (SMGs) in
relation to their dust-obscured star formation rate (SFR) and active galactic
nuclei (AGN) presence, determined using mid-IR photometry. We determined the
millimeter-wave (m) sizes of 69 ALMA-identified
SMGs, selected with confidence on ALMA images (--7.4 mJy). We found that all the SMGs are located above an
avoidance region in the millimeter size-flux plane, as expected by the
Eddington limit for star formation. In order to understand what drives the
different millimeter-wave sizes in SMGs, we investigated the relation between
millimeter-wave size and AGN fraction for 25 of our SMGs at --3. We found
that the SMGs for which the mid-IR emission is dominated by star formation or
AGN have extended millimeter-sizes, with respective median and 1.5 kpc. Instead, the SMGs for which
the mid-IR emission corresponds to star-forming/AGN composites have more
compact millimeter-wave sizes, with median
kpc. The relation between millimeter-wave size and AGN fraction suggests that
this size may be related to the evolutionary stage of the SMG. The very compact
sizes for composite star-forming/AGN systems could be explained by supermassive
black holes growing rapidly during the SMG coalescing, star-formation phase.Comment: 9 pages, 4 figures, 1 table. Accepted for publication in ApJ Lette
SXDF-ALMA 2 Arcmin^2 Deep Survey: Resolving and Characterizing the Infrared Extragalactic Background Light Down to 0.5 mJy
We present a multi-wavelength analysis of five submillimeter sources (S_1.1mm
= 0.54-2.02 mJy) that were detected during our 1.1-mm-deep continuum survey in
the SXDF-UDS-CANDELS field (2 arcmin^2, 1sigma = 0.055 mJy beam^-1) using the
Atacama Large Millimeter/submillimeter Array (ALMA). The two brightest sources
correspond to a known single-dish (AzTEC) selected bright submillimeter galaxy
(SMG), whereas the remaining three are faint SMGs newly uncovered by ALMA. If
we exclude the two brightest sources, the contribution of the ALMA-detected
faint SMGs to the infrared extragalactic background light is estimated to be ~
4.1^{+5.4}_{-3.0} Jy deg^{-2}, which corresponds to ~ 16^{+22}_{-12}% of the
infrared extragalactic background light. This suggests that their contribution
to the infrared extragalactic background light is as large as that of bright
SMGs. We identified multi-wavelength counterparts of the five ALMA sources. One
of the sources (SXDF-ALMA3) is extremely faint in the optical to near-infrared
region despite its infrared luminosity (L_IR ~ 1e12 L_sun or SFR ~ 100 M_sun
yr^{-1}). By fitting the spectral energy distributions (SEDs) at the
optical-to-near-infrared wavelengths of the remaining four ALMA sources, we
obtained the photometric redshifts (z_photo) and stellar masses (M_*): z_photo
~ 1.3-2.5, M_* ~ (3.5-9.5)e10 M_sun. We also derived their star formation rates
(SFRs) and specific SFRs (sSFRs) as ~ 30-200 M_sun yr^{-1} and ~ 0.8-2
Gyr^{-1}, respectively. These values imply that they are main-sequence
star-forming galaxies.Comment: PASJ accepted, 15 pages, 6 figures, 2 table
Nuclear Quadrupole Resonance Frequency in Multi-Layered Cuprates
The 63Cu nuclear quadrupole resonance (NQR) frequency, nu_q, in the
multi-layered cuprates is calculated in the cluster model by the exact
diagonalization method. The charge imbalance between the outer CuO_2 plane (OP)
with apical oxygen (OA) and the inner plane (IP) without OA in three-layered
Tl2223 is estimated by comparing our results with the experimental nu_q. In
Tl-based cuprates with more than three layers, we predict a large enhancement
of the splitting of nu_q between OP and IP by taking into account the reduction
of bond length between Cu and OA and a resulting enhancement of the charge
transfer energy. Our results show that the NQR frequency is a useful quantity
to estimate the charge imbalance in the multi-layered cuprates.Comment: 4 pages, 5 figure
Compact starbursts in z~3-6 submillimeter galaxies revealed by ALMA
We report the source size distribution, as measured by ALMA millimetric
continuum imaging, of a sample of 13 AzTEC-selected submillimeter galaxies
(SMGs) at z_photo ~ 3-6. Their infrared luminosities and star-formation rates
(SFR) are L_IR ~ 2-6 x 10^12 L_sun and ~ 200-600 M_sun yr-1, respectively. The
size of z ~ 3-6 SMGs ranges from 0".10 to 0".38 with a median of
0".20+0".03-0".05 (FWHM), corresponding to a median circularized effective
radius (Rc,e) of 0.67+0.13-0.14 kpc, comparable to the typical size of the
stellar component measured in compact quiescent galaxies at z ~ 2 (cQGs) --- R
~ 1 kpc. The median surface SFR density of our z ~ 3-6 SMGs is 100+42-26 M_sun
yr-1 kpc-2, comparable to that seen in local merger-driven (U)LIRGsrather than
in extended disk galaxies at low and high redshifts. The discovery of compact
starbursts in z >~ 3 SMGs strongly supports a massive galaxy formation scenario
wherein z ~ 3-6 SMGs evolve into the compact stellar components of z ~ 2 cQGs.
These cQGs are then thought to evolve into the most massive ellipticals in the
local Universe, mostly via dry mergers. Our results thus suggest that z >~ 3
SMGs are the likely progenitors of massive local ellipticals, via cQGs, meaning
that we can now trace the evolutionary path of the most massive galaxies over a
period encompassing ~ 90% of the age of the Universe.Comment: 12 pages, 10 figures, accepted to the Astrophysical Journal part
Thin accretion disk signatures of slowly rotating black holes in Ho\v{r}ava gravity
In the present work, we consider the possibility of observationally testing
Ho\v{r}ava gravity by using the accretion disk properties around slowly
rotating black holes of the Kehagias-Sfetsos solution in asymptotically flat
spacetimes. The energy flux, temperature distribution, the emission spectrum as
well as the energy conversion efficiency are obtained, and compared to the
standard slowly rotating general relativistic Kerr solution. Comparing the mass
accretion in a slowly rotating Kehagias-Sfetsos geometry in Ho\v{r}ava gravity
with the one of a slowly rotating Kerr black hole, we verify that the intensity
of the flux emerging from the disk surface is greater for the slowly rotating
Kehagias-Sfetsos solution than for rotating black holes with the same
geometrical mass and accretion rate. We also present the conversion efficiency
of the accreting mass into radiation, and show that the rotating
Kehagias-Sfetsos solution provides a much more efficient engine for the
transformation of the accreting mass into radiation than the Kerr black holes.
Thus, distinct signatures appear in the electromagnetic spectrum, leading to
the possibility of directly testing Ho\v{r}ava gravity models by using
astrophysical observations of the emission spectra from accretion disks.Comment: 12 pages, 15 figures. V2: 13 pages, clarifications and discussion
added; version accepted for publication in Classical and Quantum Gravit
Characterization of cis- and trans-acting elements in the imprinted human SNURF-SNRPN locus
The imprinted SNRPN locus is a complex transcriptional unit that encodes the SNURF and SmN polypeptides as well as multiple non-coding RNAs. SNRPN is located within the Prader-Willi and Angelman syndrome (PWS/AS) region that contains multiple imprinted genes, which are coordinately regulated by a bipartite imprinting center (IC). The SNRPN 5′ region co-localizes with the PWS-IC and contains two DNase I hypersensitive sites, DHS1 at the SNRPN promoter, and DHS2 within intron 1, exclusively on the paternally inherited chromosome. We have examined DHS1 and DHS2 to identify cis- and trans-acting regulatory elements within the endogenous SNRPN 5′ region. Analysis of DHS1 by in vivo footprinting and chromatin immunoprecipitation identified allele-specific interaction with multiple regulatory proteins, including NRF-1, which regulates genes involved in mitochondrial and metabolic functions. DHS2 acted as an enhancer of the SNRPN promoter and contained a highly conserved region that showed allele-specific interaction with unphosphorylated RNA polymerase II, YY1, Sp1 and NRF-1, further suggesting a key role for NRF-1 in regulation of the SNRPN locus. We propose that one or more of the regulatory elements identified in this study may also contribute to PWS-IC function
The Src/c-Abl pathway is a potential therapeutic target in amyotrophic lateral sclerosis
Amyotrophic lateral sclerosis (ALS), a fatal disease causing progressive loss of motor neurons, still has no effective treatment. We developed a phenotypic screen to repurpose existing drugs using ALS motor neuron survival as readout. Motor neurons were generated from induced pluripotent stem cells (iPSCs) derived from an ALS patient with a mutation in superoxide dismutase 1 (SOD1). Results of the screen showed that more than half of the hits targeted the Src/c-Abl signaling pathway. Src/c-Abl inhibitors increased survival of ALS iPSC-derived motor neurons in vitro. Knockdown of Src or c-Abl with small interfering RNAs (siRNAs) also rescued ALS motor neuron degeneration. One of the hits, bosutinib, boosted autophagy, reduced the amount of misfolded mutant SOD1 protein, and attenuated altered expression of mitochondrial genes. Bosutinib also increased survival in vitro of ALS iPSC-derived motor neurons from patients with sporadic ALS or other forms of familial ALS caused by mutations in TAR DNA binding protein (TDP-43) or repeat expansions in C9orf72. Furthermore, bosutinib treatment modestly extended survival of a mouse model of ALS with an SOD1 mutation, suggesting that Src/c-Abl may be a potentially useful target for developing new drugs to treat ALS
Effects of oxygen concentration on the proliferation and differentiation of mouse neural stem cells in vitro.
BACKGROUND AND PURPOSE: Cerebral ischemia is known to elicit the activation of neural stem cells (NSCs); however its mechanism is not fully determined. Although oxygen concentration is known to mediate many ischemic actions, there has been little attention given to the role of pathological oxygen changes under cerebral ischemia on the activation of NSCs. We investigated the effects of various oxygen concentrations on mouse neural stem cells in vitro. METHODS: NSCs were cultured from the ganglionic eminence of fetal ICR mice on embryonic day 15.5 using a neurosphere method. The effects of oxygen concentrations on proliferation, differentiation, and cell death of NSCs were evaluated by bromodeoxyuridine (BrdU) incorporation, immunocytochemistry, and TUNEL assay, respectively. RESULTS: The highest proliferation and the neuronal differentiation of the NSCs were observed in 2% oxygen, which yielded significantly higher proportions of both BrdU-labeled cells and Tuj1-positive cells when compared with 20% and 4% oxygen. On the other hand, the differentiation to the astrocytes was not affected by oxygen concentrations, except in the case of anoxia (0% oxygen). The cell death of the NSCs increased in lower oxygen conditions and peaked at anoxia. Furthermore, the switching of the neuronal subtype differentiation from GABA-positive to glutamate-positive neurons was observed in lower oxygen conditions. CONCLUSIONS: These findings raise the possibility that reduced oxygen levels occurring with cerebral ischemia enhance NSC proliferation and neural differentiation, and that mild hypoxia (2% oxygen), which is known to occur in the ischemic penumbra, is suitable for abundant neuronal differentiation
First measurement of the Hubble Constant from a Dark Standard Siren using the Dark Energy Survey Galaxies and the LIGO/Virgo Binary–Black-hole Merger GW170814
International audienceWe present a multi-messenger measurement of the Hubble constant H 0 using the binary–black-hole merger GW170814 as a standard siren, combined with a photometric redshift catalog from the Dark Energy Survey (DES). The luminosity distance is obtained from the gravitational wave signal detected by the Laser Interferometer Gravitational-Wave Observatory (LIGO)/Virgo Collaboration (LVC) on 2017 August 14, and the redshift information is provided by the DES Year 3 data. Black hole mergers such as GW170814 are expected to lack bright electromagnetic emission to uniquely identify their host galaxies and build an object-by-object Hubble diagram. However, they are suitable for a statistical measurement, provided that a galaxy catalog of adequate depth and redshift completion is available. Here we present the first Hubble parameter measurement using a black hole merger. Our analysis results in , which is consistent with both SN Ia and cosmic microwave background measurements of the Hubble constant. The quoted 68% credible region comprises 60% of the uniform prior range [20, 140] km s−1 Mpc−1, and it depends on the assumed prior range. If we take a broader prior of [10, 220] km s−1 Mpc−1, we find (57% of the prior range). Although a weak constraint on the Hubble constant from a single event is expected using the dark siren method, a multifold increase in the LVC event rate is anticipated in the coming years and combinations of many sirens will lead to improved constraints on H 0
- …