148 research outputs found
Estimating Dust Temperature and Far-IR Luminosity of High-Redshift Galaxies using ALMA Single-Band Continuum Observations
We present a method that derives the dust temperatures and infrared (IR)
luminosities of high-redshift galaxies assuming radiation equilibrium in a
simple dust and stellar distribution geometry. Using public data from the
Atacama Large Millimeter/submillimeter Array (ALMA) archive, we studied dust
temperatures assuming a clumpy interstellar medium (ISM) model for
high-redshift galaxies, then tested the consistency of our results with those
obtained using other methods. We find that a dust distribution model assuming a
clumpiness of may accurately represent
the ISM of high-redshift star-forming galaxies. By assuming a value of
, our method enables the derivation of dust temperatures and IR
luminosities of high-redshift galaxies from dust continuum fluxes and emission
sizes obtained from single-band ALMA observations. to demonstrate the method
proposed herein, we determined the dust temperature () of a star-forming galaxy, MACS0416-Y1.
Because the method only requires a single-band dust observation to derive a
dust temperature, it is more easily accessible than multi-band observations or
high-redshift emission line searches and can be applied to large samples of
galaxies in future studies using high resolution interferometers such as ALMA.Comment: Accepted for publication in MNRAS, 8 pages, 3 figures, For our public
python scripts, see https://github.com/yfudamoto/FIS22sed.gi
New Josephson Plasma Modes in Underdoped YBa2Cu3O6.6 Induced by Parallel Magnetic Field
The c-axis reflectivity spectrum of underdoped YBa2Cu3O6.6 (YBCO) is measured
below Tc=59K in parallel magnetic fields H//CuO2 up to 7T. Upon application of
a parallel field, a new peak appears at finite frequency in the optical
conductivity at the expense of suppression of c-axis condensate weight. We
conclude that the dramatic change originates from different Josephson coupling
strengths between bilayers with and without Josephson vortices. We find that
the 400cm^-1 broad conductivity peak in YBCO gains the spectral weight under
parallel magnetic field; this indicates that the condensate weight at \omega =0
is distributed to the intra-bilayer mode as well as to the new optical
Josephson mode.Comment: 4 pages, 3 figure
An investigation of the circumgalactic medium around z~2.2 AGN with ACA and ALMA
While observations of molecular gas at cosmic noon and beyond have focused on
the gas within galaxies (i.e., the interstellar medium; ISM), it is also
crucial to study the molecular gas reservoirs surrounding each galaxy (i.e., in
the circumgalactic medium; CGM). Recent observations of galaxies and quasars
hosts at high redshift (z>2) have revealed evidence for cold gaseous halos of
scale r_CGM~10kpc, with one discovery of a molecular halo with r_CGM~200kpc and
a molecular gas mass one order of magnitude larger than the ISM of the central
galaxy. As a follow-up, we present deep ACA and ALMA observations of CO(3-2)
from this source and two other quasar host galaxies at z~2.2. While we find
evidence for CO emission on scales of r~10kpc, we do not find evidence for
molecular gas on scales larger than r>20 kpc. Therefore, our deep data do not
confirm the existence of massive molecular halos on scales of ~100 kpc for
these X-ray selected quasars. As an interesting by-product of our deep
observations, we obtain the tentative detection of a negative continuum signal
on scales larger than r>200kpc, which might be tracing the Sunyaev-Zeldovich
effect associated with the halo heated by the active galactic nucleus (AGN). If
confirmed with deeper data, this could be direct evidence of the preventive AGN
feedback process expected by cosmological simulations.Comment: 17 pages, 12 figures. Accepted for publication in MNRA
Site-Dilution in quasi one-dimensional antiferromagnet Sr2(Cu1-xPdx)O3: reduction of Neel Temperature and spatial distribution of ordered moment sizes
We investigate the Neel temperature of Sr2CuO3 as a function of the site
dilution at the Cu (S=1/2) sites with Pd (S=0), utilizing the muon spin
relaxation (muSR) technique. The Neel temperature, which is Tn=5.4K for the
undoped system, becomes significantly reduced for less than one percent of
doping Pd, giving a support for the previous proposal for the good
one-dimensionality. The Pd concentration dependence of the Neel temperature is
compared with a recent theoretical study (S. Eggert, I. Affleck and M.D.P.
Horton, Phys. Rev. Lett. 89, 47202 (2002)) of weakly coupled one-dimensional
antiferromagnetic chains of S=1/2 spins, and a quantitative agreement is found.
The inhomogeneity of the ordered moment sizes is characterized by the muSR time
spectra. We propose a model that the ordered moment size recovers away from the
dopant S=0 sites with a recovery length of \xi = 150-200 sites. The origin of
the finite recovery length \xi for the gapless S=1/2 antiferromagnetic chain is
compared to the estimate based on the effective staggered magnetic field from
the neighboring chains.Comment: 10 pages, 9 figures, submitted to PR
Muon Spin Relaxation and Susceptibility Studies of Pure and Doped Spin 1/2 Kagom\'{e}-like system (CuZn)VO(OH) 2HO
Muon spin relaxation (SR) and magnetic susceptibility measurements have
been performed on the pure and diluted spin 1/2 kagom\'{e} system
(CuZn)VO(OH) 2HO. In the pure
system we found a slowing down of Cu spin fluctuations with decreasing
temperature towards K, followed by slow and nearly
temperature-independent spin fluctuations persisting down to = 50 mK,
indicative of quantum fluctuations. No indication of static spin freezing was
detected in either of the pure (=1.0) or diluted samples. The observed
magnitude of fluctuating fields indicates that the slow spin fluctuations
represent an intrinsic property of kagom\'e network rather than impurity spins.Comment: 4 pges, 4 color figures, Phys. Rev. Lett. in pres
Automated mining of the ALMA archive in the COSMOS field (A3COSMOS): II. Cold molecular gas evolution out to Redshift 6
We present new measurements of the cosmic cold molecular gas evolution out to redshift 6 based on systematic mining of the ALMA public archive in the COSMOS deep field (A3COSMOS). Our A3COSMOS dataset contains ~700 galaxies (0.3 < z < 6) with high-confidence ALMA detections in the (sub-)millimeter continuum and multi-wavelength spectral energy distributions (SEDs). Multiple gas mass calibration methods are compared and biases in band conversions (from observed ALMA wavelength to rest-frame Rayleigh-Jeans(RJ)-tail continuum) have been tested. Combining our A3COSMOS sample with ~1,000 CO-observed galaxies at 0 < z < 4 (75% at z < 0.1), we parameterize galaxies' molecular gas depletion time and molecular gas to stellar mass ratio (gas fraction) each as a function of the stellar mass, offset from the star-forming main sequence (Delta MS) and cosmic age (or redshift). Our proposed functional form provides a statistically better fit to current data (than functional forms in the literature), and implies a "downsizing" effect (i.e., more-massive galaxies evolve earlier than less-massive ones) and "mass-quenching" (gas consumption slows down with cosmic time for massive galaxies but speeds up for low-mass ones). Adopting galaxy stellar mass functions and applying our function for gas mass calculation, we for the first time infer the cosmic cold molecular gas density evolution out to redshift 6 and find agreement with CO blind surveys as well as semi-analytic modeling. These together provide a coherent picture of cold molecular gas, SFR and stellar mass evolution in galaxies across cosmic time
Probing star formation and ISM properties using galaxy disk inclination I: Evolution in disk opacity since z~0.7
Disk galaxies at intermediate redshift () have been found in previous work to display more optically thick behaviour than their local counterparts in the rest-frame B-band surface brightness, suggesting an evolution in dust properties over the past 6 Gyr. We compare the measured luminosities of face-on and edge-on star-forming galaxies at different wavelengths (Ultraviolet (UV), mid-infrared (MIR), far-infrared (FIR), and radio) for two well-matched samples of disk-dominated galaxies: a local Sloan Digital Sky Survey (SDSS)-selected sample at and a sample of disks at drawn from Cosmic Evolution Survey (COSMOS). We have derived correction factors to account for the inclination dependence of the parameters used for sample selection. We find that typical galaxies are transparent at MIR wavelengths at both redshifts and that the FIR and radio emission is also transparent as expected. However, reduced sensitivity at these wavelengths limits our analysis; we cannot rule out opacity in the FIR or radio. Ultra-violet attenuation has increased between and , with the sample being a factor of 3.4 more attenuated. The larger UV attenuation at can be explained by more clumpy dust around nascent star-forming regions. There is good agreement between the fitted evolution of the normalisation of the SFR versus 1-cos(i) trend (interpreted as the clumpiness fraction) and the molecular gas fraction/dust fraction evolution of galaxies found out to
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