We report the detection of the $^2\rm P_{3/2} \rightarrow {^2P_{1/2}}$ fine-structure line of $\rm C^+$ at 157.74 $\rm \mu m$ in SDSS J114816.64+525150.3 (hereafter J1148+5251), the most distant ...known quasar, at $z=6.42$, using the IRAM 30-m telescope. This is the first detection of the Cii line at high redshift, and also the first detection in a Hyperluminous Infrared Galaxy ($L_{\rm FIR} > 10^{13} \, L_\odot$). The Cii line is detected at a significance level of 8σ and has a luminosity of $ 4.4\times 10^9 \,L_\odot$. The $L_{\rm CII}/L_{\rm FIR}$ ratio is $\rm 2\times 10^{-4}$, about an order of magnitude smaller than observed in local normal galaxies and similar to the ratio observed in local Ultraluminous Infrared Galaxies. The Cii line luminosity indicates that the host galaxy of this quasar is undergoing an intense burst of star formation with an estimated rate of ≈$ 3000 \, M_\odot \, \rm yr^{-1}$. The detection of $\rm C^+$ in SDSS J1148+5251 suggests a significant enrichment of metals at $z\sim 6$ (age of the universe ~870 Myr), although the data are consistent with a reduced carbon to oxygen ratio as expected from chemical evolutionary models of the early phases of galaxy formation.
Abstract
We detail a new method for performing robust Bayesian estimation of the three-dimensional spatial power spectrum of the Epoch of Reionization (EoR) from interferometric observations. The ...versatility of this technique allows us to present two approaches. First, when the observations span only a small number of independent spatial frequencies (k-modes), we sample directly from the spherical power spectrum coefficients that describe the EoR signal realization. Secondly, when the number of k-modes to be included in the model becomes large, we sample from the joint probability density of the spherical power spectrum and the signal coefficients, using Hamiltonian Monte Carlo methods to explore this high-dimensional (∼20 000) space efficiently. This approach has been successfully applied to simulated observations that include astrophysically realistic foregrounds in a companion publication (Sims et al. 2016). Here, we focus on explaining the methodology in detail and use simple foreground models to both demonstrate its efficacy and highlight salient features. In particular, we show that including an arbitrary flat spectrum continuum foreground that is 108 times greater in power than the EoR signal has no detectable impact on our parameter estimates of the EoR power spectrum recovered from the data.
We present imaging data and photometry for the COSMOS survey in 15 photometric bands between 0.3 and 2.4 mu m. These include data taken on the Subaru 8.3 m telescope, the KPNO and CTIO 4 m ...telescopes, and the CFHT 3.6 m telescope. Special techniques are used to ensure that the relative photometric calibration is better than 1% across the field of view. The absolute photometric accuracy from standard-star measurements is found to be 6%. The absolute calibration is corrected using galaxy spectra, providing colors accurate to 2% or better. Stellar and galaxy colors and counts agree well with the expected values. Finally, as the first step in the scientific analysis of these data we construct panchromatic number counts which confirm that both the geometry of the universe and the galaxy population are evolving.
ABSTRACT
We present results of dust continuum and C ii$\, 158\, {\rm \mu m}$ emission line observations of a remarkably UV luminous (MUV = −21.6) galaxy at z = 10.603: GN-z11. Using the Northern ...Extended Millimeter Array (NOEMA), observations have been carried out over multiple observing cycles. We achieved a high sensitivity resulting in a $\lambda _{\rm rest}=160\, {\rm \mu m}$ continuum $1\, \sigma$ sensitivity of $13.0\, \rm {\mu Jy \, beam}^{ -1}$ and a C ii emission line $1\, \sigma$ sensitivity of $31\, \rm {mJy\, beam^{ -1}\, km \, s}^{ -1}$ using $50\, \rm {km \, s}^{ -1}$ binning with a $\sim 2\, {\rm arcsec}$ synthesized beam. Neither dust continuum nor C ii$\, 158\, {\rm \mu m}$ line emission are detected at the expected frequency of νC ii$= 163.791\, \rm {GHz}$ and the sky location of GN-z11. The upper limits show that GN-z11 is neither luminous in LIR nor LC ii, with a dust mass $3\, \sigma$ limit of ${\rm log}\, (M_{\rm dust}/{\rm {\rm M}_{\odot }}) \, \lt\, 6.5-6.9$ and with a C ii based molecular gas mass $3\, \sigma$ limit of log (Mmol, C ii$/{\rm {\rm M}_{\odot }}) \, \lt \, 9.3$. Together with radiative transfer calculations, we also investigated the possible cause of the dust poor nature of the GN-z11 showed by the blue colour in the UV continuum of GN-z11 (βUV = −2.4), and found that ≳3 × deeper observations are crucial to study dust production at very high-redshift. Nevertheless, our observations show the crucial role of deep mm/submm observations of very high-redshift galaxies to constrain multiple phases in the interstellar medium.
ABSTRACT
The 21 cm transition from neutral hydrogen promises to be the best observational probe of the epoch of reionization (EoR). The main difficulty in measuring the 21 cm signal is the presence ...of bright foregrounds that require very accurate interferometric calibration. Closure quantities may circumvent the calibration requirements but may be, however, affected by direction-dependent effects, particularly antenna primary beam responses. This work investigates the impact of antenna primary beams affected by mutual coupling on the closure phase and its power spectrum. Our simulations show that primary beams affected by mutual coupling lead to a leakage of foreground power into the EoR window, which can be up to ∼104 times higher than the case where no mutual coupling is considered. This leakage is, however, essentially confined at k < 0.3 h Mpc−1 for triads that include 29 m baselines. The leakage magnitude is more pronounced when bright foregrounds appear in the antenna sidelobes, as expected. Finally, we find that triads that include mutual coupling beams different from each other have power spectra similar to triads that include the same type of mutual coupling beam, indicating that beam-to-beam variation within triads (or visibility pairs) is not the major source of foreground leakage in the EoR window.
We explore the gas-to-dust mass ratio (M gas/M d) and the CO luminosity-to-M gas conversion factor ( Delta *aCO) of two well-studied galaxies in the Great Observatories Origins Deep Survey North ...field that are expected to have different star-forming modes, the starburst GN20 at z = 4.05 and the normal star-forming galaxy BzK-21000 at z = 1.52. Detailed sampling is available for their Rayleigh-Jeans emission via ground-based millimeter (mm) interferometry (1.1-6.6 mm) along with Herschel PACS and SPIRE data that probe the peak of their infrared emission. Using the physically motivated Draine & Li models, as well as a modified blackbody function, we measure the dust mass (M dust) of the sources and find (2.0+0.7 --0.6 X 109) M for GN20 and (8.6+0.6 --0.9 X 108) M for BzK-21000. The addition of mm data reduces the uncertainties of the derived M dust by a factor of ~2, allowing the use of the local M gas/M d versus metallicity relation to place constraints on the Delta *aCO values of the two sources. For GN20 we derive a conversion factor of Delta *aCO < 1.0 M pc--2 (K km s--1)--1, consistent with that of local ultra-luminous infrared galaxies, while for BzK-21000 we find a considerably higher value, Delta *aCO ~4.0 M pc--2 (K km s--1)--1, in agreement with an independent kinematic derivation reported previously. The implied star formation efficiency is ~25 L /M for BzK-21000, a factor of ~5-10 lower than that of GN20. The findings for these two sources support the existence of different disk-like and starburst star formation modes in distant galaxies, although a larger sample is required to draw statistically robust results.
We derive the cosmic star-formation history out to z = 1.3 using a sample of ~350 radio-selected star-forming (SF) galaxies, a far larger sample than those in previous, similar studies. We attempt to ...differentiate between radio emission from active galactic nuclei and SF galaxies, and determine an evolving 1.4 GHz luminosity function (LF) based on these VLA-COSMOS SF galaxies. We precisely measure the high-luminosity end of the SF galaxy LF (star-formation rate 100 M yr-1; equivalent to ultra-luminous IR galaxies) out to z = 1.3, finding a somewhat slower evolution than that previously derived from mid-infrared data. We find that more stars are forming in luminous starbursts at high redshift. We use extrapolations based on the local radio galaxy LF; assuming pure luminosity evolution, we derive L * (1 + z)2.1±0.2 or L * (1 + z)2.5±0.1, depending on the choice of the local radio galaxy LF. Thus, our radio-derived results independently confirm the ~1 order of magnitude decline in the CSFH since z ~ 1.
ABSTRACT Current generation low-frequency interferometers constructed with the objective of detecting the high-redshift 21 cm background aim to generate power spectra of the brightness temperature ...contrast of neutral hydrogen in primordial intergalactic medium. Two-dimensional (2D) power spectra (power in Fourier modes parallel and perpendicular to the line of sight) that formed from interferometric visibilities have been shown to delineate a boundary between spectrally smooth foregrounds (known as the wedge) and spectrally structured 21 cm background emission (the EoR window). However, polarized foregrounds are known to possess spectral structure due to Faraday rotation, which can leak into the EoR window. In this work we create and analyze 2D power spectra from the PAPER-32 imaging array in Stokes I, Q, U, and V. These allow us to observe and diagnose systematic effects in our calibration at high signal-to-noise within the Fourier space most relevant to EoR experiments. We observe well-defined windows in the Stokes visibilities, with Stokes Q, U, and V power spectra sharing a similar wedge shape to that seen in Stokes I. With modest polarization calibration, we see no evidence that polarization calibration errors move power outside the wedge in any Stokes visibility to the noise levels attained. Deeper integrations will be required to confirm that this behavior persists to the depth required for EoR detection.
Dust emission from the most distant quasars Bertoldi, F.; Carilli, C. L.; Cox, P. ...
Astronomy and astrophysics (Berlin),
08/2003, Letnik:
406, Številka:
3
Journal Article
Recenzirano
Odprti dostop
We report observations of three SDSS $z>6$ QSOs at 250 GHz (1.2 mm) using the 117-channel Max-Planck Millimeter Bolometer (MAMBO-2) array at the IRAM 30-meter telescope. J1148+5251 ($z=6.42$) and ...J1048+4637 ($z=6.23$) were detected with 250 GHz flux densities of $\rm 5.0 \pm 0.6 \,~mJy$ and $\rm 3.0 \pm 0.4 \,~mJy$, respectively. J1630+4012 ($z=6.05$) was not detected with a $3~\sigma$ upper limit of 1.8 mJy. Upper flux density limits from VLA observations at 43 GHz for J1148+5251 and J1048+4637 imply steeply rising spectra, indicative of thermal infrared emission from warm dust. The far-infrared luminosities are estimated to be ≈$10^{13} \, L_\odot$, and the dust masses ≈$ 10^8 \, M_\odot$, assuming Galactic dust properties. The presence of large amounts of dust in the highest redshift QSOs indicates that dust formation must be rapid during the early evolution of QSO host galaxies. Dust absorption may hinder the escape of ionizing photons which reionize the intergalactic medium at this early epoch.
![First detection of [CII]158...](http://api.summon.serialssolutions.com/2.0.0/image/issn/XR4PS5YY4K/0004-6361/small "First detection of [CII]158 μm at high redshift: vigorous star formation in the early universe")
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