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Register a new userALMA band 8 observations of DLA2233+131 at z=3.150
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We present our ALMA Band 8 observations of a damped Ly${alpha}$ absorption (DLA) system at $z$=3.150 observed in the spectrum of the quasar Q2233+131 at $z$=3.295. The optical counterpart of this DLA has been identified and it shows a double-peaked Ly${alpha}$ emission line. Since one possible origin of DLAs at high redshift is an outflowing gas from star-forming galaxies, DLA2233+131 provides a good laboratory to investigate the nature of high-$z$ DLAs. Motivated by this, we have carried out ALMA band 8 observations to study the [C II] line in this system. However, we do not detect any significant emission line in the observed pass bands. Instead, we have serendipitously found three submm continuum sources in the observed sky area. One appears to be the quasar Q2233+131 itself while the other two sources are newly identified submm galaxies (SMGs), called SMG1 and SMG2 in this paper. They are located at a separation of 400.7 and 800.1 from Q2233+131, respectively. Their 646 ${mu}$m fluxes are 6.35 mJy and 6.43 mJy, respectively, being higher than that of Q2233+131, 3.62 mJy. Since these two SMGs are not detected in the optical images obtained with the Hubble Space Telescope and the Subaru Telescope, they have a very red spectral energy distribution. It is, therefore,suggested that they are high-redshift galaxies or very dusty galaxies at intermediate redshift although we cannot rule out the possibility that they are optically very faint SMG analogs at low redshift. Follow up observations will be necessary to explore the nature of this interesting region.
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We have measured continuum flux densities of a high-mass protostar candidate, a radio source I in the Orion KL region (Orion Source I) using the Atacama Large Millimeter/Submillimeter Array (ALMA) at band 8 with an angular resolution of 0.1. The continuum emission at 430, 460, and 490 GHz associated with Source I shows an elongated structure along the northwest-southeast direction perpendicular to the so-called low-velocity bipolar outflow. The deconvolved size of the continuum source, 90 au times 20 au, is consistent with those reported previously at other millimeter/submillimeter wavelength. The flux density can be well fitted to the optically thick black-body spectral energy distribution (SED), and the brightness temperature is evaluated to be 700-800 K. It is much lower than that in the case of proton-electron or H- free-free radiations. Our data are consistent with the latest ALMA results by Plambeck & Wright (2016), in which the continuum emission have been proposed to arise from the edge-on circumstellar disk via thermal dust emission, unless the continuum source consists of an unresolved structure with the smaller beam filling factor.
We present deep Keck/MOSFIRE $H$-band spectroscopic observations covering the [CIII],CIII]$lambdalambda1907,1909$ doublet for three $zsim8$ galaxy candidates in the AEGIS field. Along with non-detections in two galaxies, we obtain one of the highest-redshift detections to-date of [CIII]$lambda 1907$ for the galaxy AEGIS-33376, finding $z_{rm spec}=7.945pm0.001$. We measure a [CIII]$lambda$1907 flux of $2.24pm0.71times10^{-18} mbox{ erg}mbox{ s}^{-1} mbox{ cm}^{-2}$, corresponding to a rest-frame equivalent width of $20.3pm6.5 unicode{x212B}$ for the single line. Given the not very constraining upper limit for CIII]$lambda 1909$ based on strong sky-line contamination, we assume a [CIII]$lambda$1907/CIII]$lambda 1909$ doublet ratio of 1.5 and infer a total [CIII],CIII]$lambdalambda1907,1909$ equivalent width of $33.7pm 10.8 unicode{x212B}$. We repeat the same reductions and analysis on multiple subsets of our raw data divided on the basis of time and observing conditions, verifying that the [CIII]$lambda 1907$ emission is present for AEGIS-33376 throughout our observations. We also confirm that the significance of the [CIII]$lambda 1907$ detection in different subsets of our data tracks that of brighter emission features detected on the same multi-slit mask. These multiple tests suggest that the observed emission line is real and associated with the $zsim 8$ target. The strong observed [CIII],CIII]$lambdalambda1907,1909$ in AEGIS-33376 likely indicates ISM conditions of low metallicity, high ionization parameter, and a hard ionizing spectrum, although AGN contributions are possible. This single detection represents a sizable increase in the current sample [CIII],CIII]$lambdalambda1907,1909$ detections at $z>7$, while $textit{JWST}$ will provide the first statistical samples of such measurements at these redshifts.
The ALMA Spectroscopic Survey in the Hubble Ultra Deep Field (ASPECS) Band 6 scan (212-272 GHz) covers potential [CII] emission in galaxies at $6leq z leq8$ throughout a 2.9 arcmin$^2$ area. By selecting on known Lyman-$alpha$ emitters (LAEs) and photometric dropout galaxies in the field, we perform targeted searches down to a 5$sigma$ [CII] luminosity depth $L_{mathrm{[CII]}}sim2.0times10^8$ L$_{odot}$, corresponding roughly to star formation rates (SFRs) of $10$-$20$ M$_{odot}$ yr$^{-1}$ when applying a locally calibrated conversion for star-forming galaxies, yielding zero detections. While the majority of galaxies in this sample are characterized by lower SFRs, the resulting upper limits on [CII] luminosity in these sources are consistent with the current literature sample of targeted ALMA observations of $z=6$-$7$ LAEs and Lyman-break galaxies (LBGs), as well as the locally calibrated relations between $L_{mathrm{[CII]}}$ and SFR -- with the exception of a single [CII]-deficient, UV luminous LBG. We also perform a blind search for [CII]-bright galaxies that may have been missed by optical selections, resulting in an upper limit on the cumulative number density of [CII] sources with $L_{mathrm{[CII]}}>2.0times10^8$ L$_{odot}$ ($5sigma $) to be less than $1.8times10^{-4}$ Mpc$^{-3}$ (90% confidence level). At this luminosity depth and volume coverage, we present an observed evolution of the [CII] luminosity function from $z=6$-$8$ to $zsim0$ by comparing the ASPECS measurement to literature results at lower redshift.
Similarly to the cosmic star formation history, the black hole accretion rate density of the Universe peaked at 1<z<3. This cosmic epoch is hence best suited for investigating the effects of radiative feedback from AGN. Observational efforts are underway to quantify the impact of AGN feedback, if any, on their host galaxies. Here we present a study of the molecular gas content of AGN hosts at z~1.5 using CO[2-1] line emission observed with ALMA for a sample of 10 AGNs. We compare this with a sample of galaxies without an AGN matched in redshift, stellar mass, and star formation rate. We detect CO in 3 AGNs with $mathrm{L_{CO} sim 6.3-25.1times 10^{9} L_{odot}}$ which translates to a molecular hydrogen gas mass of $mathrm{2.5-10times 10^{10} M_{odot}}$ assuming conventional conversion factor of $mathrm{alpha_{CO}}sim3.6$. Our results indicate a >99% probability of lower depletion time scales and lower molecular gas fractions in AGN hosts with respect to the non-AGN comparison sample. We discuss the implications of these observations on the impact that AGN feedback may have on star formation efficiency of z>1 galaxies.
We present ALMA band-7 data of the [CII] $lambda157.74,mu{rm m}$ emission line and underlying far-infrared (FIR) continuum for twelve luminous quasars at $z simeq 4.8$, powered by fast-growing supermassive black holes (SMBHs). Our total sample consists of eighteen quasars, twelve of which are presented here for the first time. The new sources consists of six Herschel/SPIRE detected systems, which we define as FIR-bright sources, and six Herschel/SPIRE undetected systems, which we define as FIR-faint sources. We determine dust masses for the quasars hosts of $M_{dust} le 0.2-25.0times 10^8 M_{odot}$, implying ISM gas masses comparable to the dynamical masses derived from the [CII] kinematics. It is found that on average the MgII line is blueshifted by $sim 500,{rm km,s}^{-1}$ with respect to the [CII] emission line, which is also observed when complementing our observations with data from the literature. We find that all of our FIR-bright subsample and most of the FIR-faint objects lie above the main sequence of star forming galaxies at $z sim 5$. We detect companion sub-millimeter galaxies (SMGs) for two sources, both FIR-faint, with a range of projected distances of $sim20-60$ kpc and with typical velocity shifts of $left|Delta vright| lesssim200,{rm km,s}^{-1}$ from the quasar hosts. Of our total sample of eighteen quasars, 5/18 are found to have dust obscured starforming companions.
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