17 research outputs found
Anomalous microwave emission from spinning nanodiamonds around stars
Several interstellar environments produce 'anomalous microwave emission'
(AME), with brightness peaks at tens-of-gigahertz frequencies. The
emission's origins are uncertain -- rapidly spinning nanoparticles could
emit electric-dipole radiation, but the polycyclic aromatic hydrocarbons
that have been proposed as the carrier are now found not to correlate
with Galactic AME signals. The difficulty is in identifying co-spatial
sources over long lines of sight. Here we identify AME in three
proto-planetary discs. These are the only known systems that host
hydrogenated nanodiamonds, in contrast to the very common detection of
polycyclic aromatic hydrocarbons. Using spectroscopy, the nanodiamonds
are located close to the host stars, at physically well-constrained
temperatures. Developing disc models, we reproduce the emission with
diamonds 0.75--1.1 nm in radius, holding <= 1-2% of the carbon budget.
Ratios of microwave emission to stellar luminosity are approximately
constant, allowing nanodiamonds to be ubiquitous but emitting below
detection thresholds in many star systems. This result is compatible
with the findings with similar-sized diamonds found within Solar System
meteorites. As nanodiamond spectral absorption is seen in interstellar
sightlines, these particles are also a candidate for generating
galaxy-scale AME
Molecular Gas in Quasar Hosts
The study of molecular gas in quasar host galaxies addresses a number of interesting questions pertaining to the hosts' ISM, to unified schemes relating quasars and IR galaxies, and to the processes fueling nuclear activity. In this contribution I review observations of molecular gas in quasar hosts from z=0.06 to z=4.7. The Cloverleaf quasar at z=2.5 is featured as a case where there are now enough detected transitions (four in CO, and one each in CI and HCN) to allow detailed modeling of physical conditions in the molecular ISM. We find that the CO-emitting gas is warmer, denser, and less optically thick than that found in typical Galactic molecular clouds. These differences are probably due to the presence of the luminous quasar in the nucleus of the Cloverleaf's host galaxy
Cold Gas at High Redshift
We discuss the current observational and theoretical issues concerning cold
gas at high redshift and present simulations showing how a number of
observational issues can be resolved with planned future instrumentation.Comment: 13 page LaTeX requires crckapb.sty and psfig.sty, 9 compressed and
tarred postscript figures (410kB) available at
ftp://ftp.nfra.nl/pub/outgoing/rbraun/coldghiz/figs.tar.Z Complete compressed
postscript paper (475kB) available at
ftp://ftp.nfra.nl/pub/outgoing/rbraun/coldghiz/paper.ps.Z To appear in "Cold
Gas at High Redshift", Eds. M.Bremer et al. (Kluwer, Dordrecht
Recommended from our members
Anomalous microwave emission from spinning nanodiamonds around stars
Several interstellar environments produce 'anomalous microwave emission'
(AME), with brightness peaks at tens-of-gigahertz frequencies. The
emission's origins are uncertain -- rapidly spinning nanoparticles could
emit electric-dipole radiation, but the polycyclic aromatic hydrocarbons
that have been proposed as the carrier are now found not to correlate
with Galactic AME signals. The difficulty is in identifying co-spatial
sources over long lines of sight. Here we identify AME in three
proto-planetary discs. These are the only known systems that host
hydrogenated nanodiamonds, in contrast to the very common detection of
polycyclic aromatic hydrocarbons. Using spectroscopy, the nanodiamonds
are located close to the host stars, at physically well-constrained
temperatures. Developing disc models, we reproduce the emission with
diamonds 0.75--1.1 nm in radius, holding <= 1-2% of the carbon budget.
Ratios of microwave emission to stellar luminosity are approximately
constant, allowing nanodiamonds to be ubiquitous but emitting below
detection thresholds in many star systems. This result is compatible
with the findings with similar-sized diamonds found within Solar System
meteorites. As nanodiamond spectral absorption is seen in interstellar
sightlines, these particles are also a candidate for generating
galaxy-scale AME
Recommended from our members
A Study of CO Emission in High-Redshift QSOs Using the Owens Valley Millimeter Array
Searches for CO emission in high-redshift objects have traditionally suffered from the accuracy of optically derived redshifts for lack of bandwidth in correlators at radio observatories. This problem has motivated the creation of the new COBRA continuum correlator with 4 GHz available bandwidth at the Owens Valley Radio Observatory Millimeter Array. Presented here are the first scientific results from COBRA. We report detections of redshifted CO (J = 3 → 2) emission in the QSOs SMM J04135+10277 and VCV J140955.5+562827, as well as a probable detection in RX J0911.4+0551. At redshifts of z = 2.846, 2.585, and 2.796, we find integrated CO flux densities of 5.4, 2.4, and 2.9 Jy km s-1 for SMM J04135+10277, VCV J140955.5+562827, and RX J0911.4+0551, respectively, over line widths of ΔVFWHM ~ 350 km s-1. These measurements, when corrected for gravitational lensing, correspond to molecular gas masses of order M(H2) ~ 109.6-1011.1 M and are consistent with previous CO observations of high-redshift QSOs. We also report 3 σ upper limits on CO (3 → 2) emission in the QSO LBQS 0018-0220 of 1.3 Jy km s-1. We do not detect significant 3 mm continuum emission from any of the QSOs, with the exception of a tentative (3 σ) detection in RX J0911.4+0551 of S3 mm = 0.92 mJy beam-1
Mid-infrared spectroscopy of high-redshift submillimeter galaxies:First results
We present mid-infrared spectra of five submillimeter galaxies at z = 0.65-2.38 taken with the Spitzer Space Telescope. Four of these sources, at z ≾ 1.5, have strong PAH features and their composite spectrum is well fitted by an M82-like spectrum with an additional power-law component consistent with that expected from AGN activity. Based on comparison with local templates of the 7.7 μm PAH equivalent width and the PAH-to-infrared luminosity ratio, we conclude that these galaxies host both star formation and AGN activity, with star formation dominating the bolometric luminosity. The source at z = 2.38 displays a Mrk 231-type broad emission feature at rest frame ~8 μm that does not conform to the typical 7.7 μm/8.6 μm PAH complex in starburst galaxies, suggesting a more substantial AGN contribution
Molecular gas and dust properties of galaxies from the Great Observatories All-sky LIRG Survey
We present IRAM-30 m Telescope (CO)-C-12 and (CO)-C-13 observations of a sample of 55 luminous and ultraluminous infrared galaxies (LIRGs and ULIRGs) in the local universe. This sample is a subset of the Great Observatory All-Sky LIRG Survey (GOALS), for which we use ancillary multi-wavelength data to better understand their interstellar medium and star formation properties. Fifty-three (96%) of the galaxies are detected in (CO)-C-12, and 29 (52%) are also detected in (CO)-C-13 above a 3 sigma level. The median full width at zero intensity (FWZI) velocity of the CO line emission is 661 km s(-1), and similar to 54% of the galaxies show a multi-peak CO profile. Herschel photometric data is used to construct the far-IR spectral energy distribution of each galaxy, which are fit with a modified blackbody model that allows us to derive dust temperatures and masses, and infrared luminosities. We make the assumption that the gas-to-dust mass ratio of (U)LIRGs is comparable to local spiral galaxies with a similar stellar mass (i.e., gas/dust of mergers is comparable to their progenitors) to derive a CO-to-H-2 conversion factor of = 1.8(-0.8)(+1.3) M-circle dot (K km s(-1) pc(2))(-1); such a value is comparable to that derived for (U)LIRGs based on dynamical mass arguments. We derive gas depletion times of 400 600 Myr for the (U)LIRGs, compared to the 1.3 Gyr for local spiral galaxies. Finally, we re-examine the relationship between the (CO)-C-12/(CO)-C-13 ratio and dust temperature, confirming a transition to elevated ratios in warmer systems.© ESO 2019We thank the anonymous referee for the useful comments. We also thank Nick Scoville for his discussion and comments on the paper. We are grateful to Manuel Gonzalez for his help in the preparation of the scripts and during the observations. This work is based on observations carried out under project numbers 099-10, 092-11, 227-11, 076-12, 222-13, and D01-13 with the 30m telescope. IRAM is supported by INSU/CNRS (France), MPG (Germany), and IGN (Spain). We thank the director of IRAM 30m for the approval of the discretionary time requested. RHI, MAPT, and AA acknowledge support from the Spanish MINECO through grants AYA2012-38491-C020-2 and AYA2015-63939-C2-1-P.G.C.P. was supported by a FONDECYT Postdoctoral Fellowship (No. 3150361). G.C.P. also acknowledges support from the University of Florida. G.C.P. and A.S.E. were supported by the NSF grant AST 1109475. A.S.E. was also supported by the Taiwan, R.O.C. Ministry of Science and technology grant MoST 102-2119-M-001-MY3. T.D.-S. acknowledges support from ALMA-CONICYT project 31130005 and FONDECYT regular project 1151239. This work was supported in part by National Science Foundation grant No. PHYS-1066293 and the hospitality of the Aspen Center for Physics. This research has made use of the NASA/IPAC Extragalactic Database (NED), which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration
Recommended from our members
On the redshift distribution and physical properties of ACT-selected DSFGs
We present multi-wavelength detections of nine candidate gravitationally lensed dusty starforming galaxies (DSFGs) selected at 218 GHz (1.4 mm) from the Atacama Cosmology Telescope (ACT) equatorial survey. Among the brightest ACT sources, these represent the subset of the total ACT sample lying in Herschel SPIRE fields, and all nine of the 218 GHz detections were found to have bright Herschel counterparts. By fitting their spectral energy distributions (SEDs) with a modified blackbody model with power-law temperature distribution, we find the sample has a median redshift of z = 4.1(-1.0)(+1.1) (68 per cent confidence interval), as expected for 218 GHz selection, and an apparent total infrared luminosity of log10(mu LIR/L-circle dot) = 13.86(-0.30)(+0.33), which suggests that they are either strongly lensed sources or unresolved collections of unlensed DSFGs. The effective apparent diameter of the sample is root mu d = 4.2(-1.0)(+1.7) kpc, further evidence of strong lensing or multiplicity, since the typical diameter of DSFGs is 1.0-2.5 kpc. We emphasize that the effective apparent diameter derives from SED modelling without the assumption of optically thin dust (as opposed to image morphology). We find that the sources have substantial optical depth (tau = 4.2(-1.9)(+3.7)) to dust around the peak in the modified blackbody spectrum (lambda(obs) <= 500 mu m), a result that is robust to model choice
Identification of luminous infrared galaxies at 1
We present preliminary results on 24micron detections of luminous infrared galaxies at z>1 with the Multiband Imaging Photometer for Spitzer (MIPS). Observations were performed in the Lockman Hole and the Extended Groth Strip (EGS), and were supplemented by data obtained with the Infrared Array Camera (IRAC) between 3 and 9microns. The positional accuracy of ~2arcsec for most MIPS/IRAC detections provides unambiguous identifications of their optical counterparts. Using spectroscopic redshifts from the Deep Extragalactic Evolutionary Probe survey, we identify 24micron sources at z>1 in the EGS, while the combination of the MIPS/IRAC observations with ancillary data in the Lockman Hole also shows very clear cases of galaxies with photometric redshifts at 1=M*) galaxy counterparts. It is the first time that this population of luminous objects is detected up to z~2.5 in the infrared. Our work demonstrates the ability of the MIPS instrument to probe the dusty Universe at very high redshift, and illustrates how the forthcoming Spitzer deep surveys will offer a unique opportunity to illuminate a dark side of cosmic history not explored by previous infrared experiments.</z<2.5.