79 research outputs found
A comprehensive analysis of optical and near-infrared spectroscopy of z~6 quasars
High redshift (z~6) quasars (QSOs) are unique probes of the early growth of accreting supermassive black holes (BHs) and are fundamental tools to study the ionization state of the intergalactic medium and its chemical enrichment. Until now, only the most luminous QSOs have been studied, often one object at the time. In this thesis we present the most extended consistent analysis to date of optical and near-infrared spectra of z~6 QSOs. Our NIR sample is composed of 22 spectra of QSOs at 4.5<z<6.45, covering the MgII and FeII emission features, and includes new spectroscopic VLT-ISAAC observations of three faint z~6 SDSS QSOs. The optical sample consists of 26 high quality spectra of QSOs at 5.70<z<6.45, covering the Ly-alpha complex, and the OI+SiII, CII and SiIV+OIV] broad lines. Based on the NIR spectra we estimate the BH mass (MBH), the Eddington ratio and the FeII/MgII line ratio, a proxy for the chemical enrichment of the BLR. The QSOs in our sample host BHs with masses of ~10^9 Msun that are accreting significantly faster than a luminosity–matched comparison sample at lower redshifts. The measured FeII/MgII line ratios show no evolution with cosmic time in the redshift range 4.5<z<6.45, implying that the QSOs in our sample have undergone a major episode of Fe enrichment in the few 100s Myr preceding the cosmic age at which they are observed. An analysis of the wavelength shifts of the optical lines shows that the redshifts inferred from the OI+SiII complex, visible in most of the optical spectra, are consistent with those obtained from the MgII line. This implies that zOI is a reliable proxy for the QSO systemic redshift. We create a composite template of the z~6 QSOs that, red-ward the Ly-alpha line, remarkably resembles the one obtained for low-redshift QSOs. Investigating the existence of possible correlations amongst optical emission properties, we do not detect the expected anti-correlation between the EW and the QSO continuum luminosity (Baldwin effect) for the high ionization lines (NV & SiIV+OIV]). We show that a strong correlation holds between the line FWHM and its luminosity. Given the narrow distribution of Eddington ratios that characterizes the z~6 QSOs population, this implies that QSOs with brighter lines are the ones that host more massive BHs. We further confirm this statement by testing the relation between the line luminosity and MBH. Finally we use our optical spectra to study the ionization state of the IGM at high redshift, by measuring the evolution of the near zone (NZ) sizes and that of the Gunn Peterson (GP) effective optical depth. Our comprehensive analysis shows that the correlation between the NZ radii and the QSO systemic redshifts is significantly reduced with respect to previous results. This implies that changes of the IGM ionization state are difficult to constrain through such measurements. We also outline a new method to detect the evolution of the GP effective optical depth through the analysis of the Ly-alpha and Ly-beta flux ratios. For each QSO we build a model based on the SDSS QSO composite spectrum and on the optical depth parametrization of lower-redshift absorbers (z<5.7). Comparing the QSOs flux ratios with the ones obtained from the models we detect a steep increase in the evolution of the effective optical depth
Detection of Dust in High-Velocity Cloud Complex C -- Enriched Gas Accreting onto the Milky Way
We present the detection of dust depletion in Complex C, a massive,
infalling, low-metallicity high-velocity cloud in the northern Galactic
hemisphere that traces the ongoing accretion of gas onto the Milky Way. We
analyze a very high signal-to-noise HST/COS spectrum of AGN Mrk 817 formed by
coadding 165 individual exposures taken under the AGN STORM 2 program, allowing
us to determine dust-depletion patterns in Complex C at unprecedented
precision. By fitting Voigt components to the O I, S II, N I, Si II, Fe II, and
Al II absorption and applying ionization corrections from customized Cloudy
photoionization models, we find sub-solar elemental abundance ratios of
[Fe/S]=-0.42+/-0.08, [Si/S]=-0.29+/-0.05, and [Al/S]=-0.53+/-0.08. These ratios
indicate the depletion of Fe, Si, and Al into dust grains, since S is mostly
undepleted. The detection of dust provides an important constraint on the
origin of Complex C, as dust grains indicate the gas has been processed through
galaxies, rather than being purely extragalactic. We also derive a low
metallicity of Complex C of [S/H]=-0.51+/-0.16 (31% solar), confirming earlier
results from this sightline. We discuss origin models that could explain the
presence of dust in Complex C, including Galactic fountain models, tidal
stripping from the Magellanic Clouds or other satellite galaxies, and
precipitation of coronal gas onto dust-bearing ``seed" clouds.Comment: 8 pages, 3 figures, accepted for publication in ApJ Letters. This
version has been updated with proof correction
The First High Redshift Quasar from Pan-STARRS
We present the discovery of the first high redshift (z > 5.7) quasar from the
Panoramic Survey Telescope and Rapid Response System 1 (Pan-STARRS1 or PS1).
This quasar was initially detected as an i dropoutout in PS1, confirmed
photometrically with the SAO Widefield InfraRed Camera (SWIRC) at Arizona's
Multiple Mirror Telescope (MMT) and the Gamma-Ray Burst Optical/Near-Infrared
Detector (GROND) at the MPG 2.2 m telescope in La Silla. The quasar was
verified spectroscopically with the the MMT Spectrograph, Red Channel and the
Cassegrain Twin Spectrograph (TWIN) at the Calar Alto 3.5 m telescope. It has a
redshift of 5.73, an AB z magnitude of 19.4, a luminosity of 3.8 x 10^47 erg/s
and a black hole mass of 6.9 x 10^9 solar masses. It is a Broad Absorption Line
quasar with a prominent Ly-beta peak and a very blue continuum spectrum. This
quasar is the first result from the PS1 high redshift quasar search that is
projected to discover more than a hundred i dropout quasars, and could
potentially find more than 10 z dropout (z > 6.8) quasars.Comment: 8 pages, 7 figure
The VMC survey - XI : Radial Stellar Population Gradients in the Galactic Globular Cluster 47 Tucanae
Copyright American Astronomical SocietyWe present a deep near-infrared color-magnitude diagram of the Galactic globular cluster 47 Tucanae, obtained with the Visible and Infrared Survey Telescope for Astronomy (VISTA) as part of the VISTA near-infrared Y, J, Ks survey of the Magellanic System (VMC). The cluster stars comprising both the subgiant and red giant branches exhibit apparent, continuous variations in color-magnitude space as a function of radius. Subgiant branch stars at larger radii are systematically brighter than their counterparts closer to the cluster core; similarly, red-giant-branch stars in the cluster's periphery are bluer than their more centrally located cousins. The observations can very well be described by adopting an age spread of ~0.5 Gyr as well as radial gradients in both the cluster's helium abundance (Y) and metallicity (Z), which change gradually from (Y = 0.28, Z = 0.005) in the cluster core to (Y = 0.25, Z = 0.003) in its periphery. We conclude that the cluster's inner regions host a significant fraction of second-generation stars, which decreases with increasing radius; the stellar population in the 47 Tuc periphery is well approximated by a simple stellar population.Peer reviewe
Consensus on the delphi method of priority nursing diagnosis for heart failure in primary care / Consenso pelo método Delphi de diagnósticos de enfermagem prioritários para insuficiência cardíaca na atenção primária
Objetivo: descrever e analisar o processo da seleção dos diagnósticos de enfermagem prioritários para o cuidado enfermagem aos indivíduos nos diferentes estágios de insuficiência cardíaca, na atenção primária. Método: trata-se de um recorte de pesquisa, constituído por fase metodológica, com a aplicação da técnica Delphi junto a especialistas referente a 176 diagnósticos de enfermagem segundo a Taxonomia NANDA-I no período de dezembro de 2012 a julho de 2013.Resultados: 144 diagnósticos foram identificados como não prioritários e 32 foram selecionados como diagnósticos de enfermagem prioritários, agregados neste estudo como: “sinal de gravidade”; “conhecimento/atitude/prática”; “sintoma”; e “risco”. Conclusão: o mapa gerado por esse esforço fez-se útil para orientar a busca da prevalência de cada diagnóstico e sobretudo para propor intervenções em saúde na atenção primária direcionadas às necessidades dos indivíduos saudáveis, com diagnóstico clínico de insuficiência cardíaca ou com risco para o seu desenvolvimento
The X-SHOOTER/ALMA sample of Quasars in the Epoch of Reionization. I. NIR spectral modeling, iron enrichment and broad emission line properties
We present X-SHOOTER near-infrared spectroscopy of a large sample of 38
luminous ( to ) quasars at , which have
complementary CII observations from ALMA. This X-SHOOTER/ALMA sample provides
us with the most comprehensive view of reionization-era quasars to date,
allowing us to connect the quasar properties with those of its host galaxy. In
this work we introduce the sample, discuss data reduction and spectral fitting,
and present an analysis of the broad emission line properties. The measured
FeII/MgII flux ratio suggests that the broad line regions of all quasars in the
sample are already enriched in iron. We also find the MgII line to be on
average blueshifted with respect to the CII redshift with a median of
. A significant correlation between the MgII-CII
and CIV-CII velocity shifts indicates a common physical origin. Furthermore, we
frequently detect large CIV-MgII emission line velocity blueshifts in our
sample with a median value of . While we find all
other broad emission line properties not to be evolving with redshift, the
median CIV-MgII blueshift is much larger than found in low-redshift,
luminosity-matched quasars (). Dividing our sample
into two redshift bins, we confirm an increase of the average CIV-MgII
blueshift with increasing redshift. Future observations of the rest-frame
optical spectrum with the James Webb Space Telescope will be instrumental in
further constraining the possible evolution of quasar properties in the epoch
of reionization.Comment: ApJ accepte
The Cepheid Distance to the Narrow-Line Seyfert 1 Galaxy NGC 4051
We derive a distance of ~Mpc (~mag) to
the archetypal narrow-line Seyfert 1 galaxy NGC 4051 based on Cepheid
Period--Luminosity relations and new Hubble Space Telescope multiband imaging.
We identify 419 Cepheid candidates and estimate the distance at both optical
and near-infrared wavelengths using subsamples of precisely-photometered
variables (123 and 47 in the optical and near-infrared subsamples,
respectively). We compare our independent photometric procedures and
distance-estimation methods to those used by the SH0ES team and find agreement
to 0.01~mag. The distance we obtain suggests an Eddington ratio for NGC 4051, typical of narrow-line Seyfert 1 galaxies, unlike
the seemingly-odd value implied by previous distance estimates. We derive a
peculiar velocity of ~km~s for NGC 4051, consistent with the
overall motion of the Ursa Major Cluster in which it resides. We also revisit
the energetics of the NGC 4051 nucleus, including its outflow and mass
accretion rates.Comment: 15 pages, 12 figures, 6 tables, accepted for publication in Ap
The X-shooter/ALMA Sample of Quasars in the Epoch of Reionization. II. Black Hole Masses, Eddington Ratios, and the Formation of the First Quasars
We present measurements of black hole masses and Eddington ratios for a
sample of 38 bright (M < -24.4 mag) quasars at 5.8 < z < 7.5, derived
from VLT/X-shooter near-IR spectroscopy of their broad CIV and MgII emission
lines. The black hole masses (on average M ~ 4.6 x 10 M)
and accretion rates (with Eddington ratios ranging between 0.1 and 1.0) are
broadly consistent with that of similarly luminous 0.3 < z < 2.3 quasars, but
there is evidence for a mild increase in the median Eddington ratio going
towards z > 6. Combined with deep ALMA observations of the [CII] 158 m
line from the quasar host galaxies and VLT/MUSE investigations of the extended
Ly halos, this study provides fundamental clues to models of the
formation and growth of the first massive galaxies and black holes. Compared to
local scaling relations, z > 5.7 black holes appear to be over-massive with
respect to their host galaxies, and their accretion properties do not change
with host galaxy morphology. Under the assumption that the kinematics of the T
~ 10 K gas, traced by the extended Ly halos, are dominated by the
gravitational potential of the dark matter halo, we report a similar relation
between the black hole mass and circular velocity to the one reported for z ~ 0
galaxies. These results paint a picture where the first supermassive black
holes reside in massive halos at z > 6 and lead the first stages of galaxy
formation by rapidly growing in mass with a duty cycle of order unity. However,
this duty cycle needs to drastically drop towards lower redshifts, while the
host galaxies continue forming stars at a rate of hundreds of solar masses per
year, sustained by the large reservoirs of cool gas surrounding them.Comment: Accepted for publication on AAS journals. 24 pages + appendices, 15
figures, 5 tables (including full list of z>5.7 quasars with MgII based black
hole mass estimates). For access to the data and codes used in this work,
please contact the author
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