Metallicity and black hole masses of z6 quasars Kurk, Jaron D; Walter, Fabian; Riechers, Dominik ...
Proceedings of the International Astronomical Union,
08/2006, Volume:
2, Issue:
14
Journal Article
Peer reviewed
Abstract We present NIR spectroscopy of emission lines of a sample of five z6 quasars, including fainter objects than observed before. The measured FeII/MgII ratios are around solar and consistent ...with a lack of evolution of the metallicity of quasar BLRs up to z6, suggesting that stars in their hosts formed at z6. The BH masses, measured from both MgII and CIV line widths are within the range 2-16x108M, the smallest found in such distant objects. PUBLICATION ABSTRACT
The ALMA Spectroscopic Survey in the Hubble Ultra Deep Field (ASPECS) Band 6
scan (212-272 GHz) covers potential CII emission in galaxies at $6\leq z
\leq8$ 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
$L_{\mathrm{CII}}\sim2.0\times10^8$ 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 $L_{\mathrm{CII}}>2.0\times10^8$ L$_{\odot}$ ($5\sigma $) to be less
than $1.8\times10^{-4}$ 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 $z\sim0$ by comparing the ASPECS
measurement to literature results at lower redshift.
The high-frequency radio sky has historically remained largely unexplored due to the typical faintness of sources in this regime, and the modest survey speed compared to observations at lower ...frequencies. However, high-frequency radio surveys present an invaluable tracer of high-redshift star-formation, as they directly target the faint radio free-free emission. We present deep continuum observations at 34 GHz in the COSMOS and GOODS-North fields from the Karl G. Jansky Very Large Array (VLA), as part of the COLDz survey. The deep COSMOS mosaic spans \(\sim10\text{arcmin}^2\) down to \(\sigma=1.3\mu\text{Jy beam}^{-1}\), while the wider GOODS-N observations cover \(\sim50\text{arcmin}^2\) to \(\sigma=5.3\mu\text{Jy beam}^{-1}\). We present the deepest 34 GHz radio number counts to date, with five and thirteen continuum detections in COSMOS and GOODS-N, respectively. Nine galaxies show 34 GHz continuum emission that is originating from star-formation, although for two sources this is likely due to thermal emission from dust. Utilizing deep ancillary radio data at 1.4, 3, 5 and 10 GHz, we decompose the spectra of the remaining seven star-forming galaxies into their synchrotron and thermal free-free components, finding typical thermal fractions and synchrotron spectral indices comparable to those observed in local star-forming galaxies. Using calibrations from the literature, we determine free-free star-formation rates (SFRs), and show that these are in agreement with SFRs from spectral energy distribution fitting and the far-infrared/radio correlation. Our observations place strong direct constraints on the high-frequency radio emission in typical galaxies at high-redshift, and provide some of the first insight in what is set to become a key area of study with future radio facilities as the Square Kilometer Array Phase 1 and next-generation VLA.
The goal of this science case is to accurately pin down the molecular gas
content of high redshift galaxies. By targeting the CO ground transition, we
circumvent uncertainties related to CO ...excitation. The ngVLA can observe the
CO(1-0) line at virtually any $z>1.5$, thus exposing the evolution of gaseous
reservoirs from the earliest epochs down to the peak of the cosmic history of
star formation. The order-of-magnitude improvement in the number of CO
detections with respect to state-of-the-art observational campaigns will
provide a unique insight on the evolution of galaxies through cosmic time.
The goal of this science case is to study physical conditions of the
interstellar medium (ISM) in distant galaxies. In particular, its densest
component is associated with the inner cores of clouds ...-- this is where star
formation takes place. Carbon monoxide is usually used to trace molecular gas
emission; however, its transitions are practically opaque, thus preventing
astronomers from piercing through the clouds, into the deepest layers that are
most intimately connected with the formation of stars. Other dense gas tracers
are required, although they are typically too faint and/or at too low
frequencies to be effectively observed in high redshift galaxies. The ngVLA
will offer for the first time the sensitivity at radio frequencies that is
needed to target CI$_{1-0}$ (at $z>5$), as well as the ground transitions of
dense gas tracers of the ISM such as HCN, HNC, HCO+ (at various redshifts
$z>1$), beyond the tip of the iceberg of the hyper-luminous sources that could
be studied up to now. These new tools will critically contribute to our
understanding of the intimate interplay between gas clouds and star formation
in different environments and cosmic epochs.
The goal of this science case is to address the use of a ngVLA as a CO redshift machine for dust-obscured high-redshift galaxies which lack of clear counterparts at other wavelengths. Thanks to its ...unprecedentedly large simultaneous bandwidth and sensitivity, the ngVLA will be able to detect low--J CO transitions at virtually any \(z>1\). In particular, at \(z>4.76\) two CO transitions will be covered in a single frequency setting, thus ensuring unambiguous line identification. The ngVLA capabilities fill in a redshift range where other approaches (e.g., photometric redshifts, search for optical/radio counterparts, etc) typically fail due to the combination of intrinsically faint emission and increasing luminosity distance. This will allow us to explore the formation of massive galaxies in the early cosmic times.
The chomosomal location of a glutathione S-transferase (GST) gene was determined in both hexaploid wheat (Triticum aestivum) and barley (Hordeum vulgare). The GST cDNA used to map the gene was cloned ...from the diploid wheat Triticum tauschii. GST loci were located on the short arms of chromosomes 6A, 6B, and 6D in T. aestivum and also on the short arm of chromosome 6H in H. vulgare. The GST locus in barley was absolutely linked to the RFLP marker E148A and was located 0.8 cM proximal to the RFLP marker ABC169B on barley chromosome 6H. At least two copies of the GST gene were present in each of the T. aestivum A, B, and D genomes, and a homologous GST gene was present as a single-copy gene in the barley genome. GST mRNA transcripts were not detected in RNA isolated from shoots of control (unsafened) seedlings of T. tauschii or T. aestivum. It was determined that the expression of the GST gene was regulated by herbicide safener treatment in T. tauschii and T. aestivum by detecting safener-increased GST mRNA transcript levels.
PDF
