61 research outputs found
Towards sub-kpc scale kinematics of molecular and ionized gas of star-forming galaxies at z similar to 1
We compare the molecular and ionized gas kinematics of two strongly lensed
galaxies at based on observations from ALMA and MUSE. We derive the CO
and [OII] rotation curves and dispersion profiles of these two galaxies. We
find a difference between the observed molecular and ionized gas rotation
curves for one of the galaxies, the Cosmic Snake, for which we obtain a spatial
resolution of few hundred parsecs along the major axis. The rotation curve of
the molecular gas is steeper than the rotation curve of the ionized gas. In the
second galaxy, A521, the molecular and ionized gas rotation curves are
consistent, but the spatial resolution is only of few kpc on the major axis.
Using simulations, we investigate the effect of the thickness of the gas disk
and effective radius on the observed rotation curves and find that a more
extended and thicker disk smooths the curve. We also find that the presence of
a strongly inclined thick disk (>1 kpc) can smooth the rotation curve because
it degrades the spatial resolution along the line of sight. By building a model
using a stellar disk and two gas disks, we reproduce the rotation curves of the
Cosmic Snake with a molecular gas disk that is more massive and more radially
and vertically concentrated than the ionized gas disk. Finally, we also obtain
an intrinsic velocity dispersion in the Cosmic Snake of 18.5+-7 km/s and
19.5+-6 km/s for the molecular and ionized gas, respectively, which is
consistent with a molecular disk with a smaller and thinner disk. For A521, the
intrinsic velocity dispersion values are 11+-8 km/s and 54+-11 km/s, with a
higher value for the ionized gas. This could indicate that the ionized gas disk
is thicker and more turbulent in this galaxy. These results highlight the
different spatial distribution of the molecular and ionized gas disks at
and suggest the presence of thick ionized gas disks at this epoch.Comment: 11 pages, 8 figures, accepted for publication in A&
Results of hydrological studies and channel analysis of the Ganges (Padma) River at the construction site of the “Rooppur” NPP
This work presents the results of research on channel processes in the Padma River (Republic of Bangladesh) at the construction site of the “Ruppur” Nuclear Power Plant (NPP). The fluvial characteristics of the Padma River were presented, including: the water outflow regime, characteristics of anthropogenic impact on the river outflow and assessment of the present state of the channel and floodplain. The research was conducted based on field expeditions, during which data on morphology, dynamics, hydrological and hydraulic conditions for the formation of the floodplain-channel complex were collected. Moreover, the water discharges and suspended sediments, as well as the longitudinal profiles of the water level and the channel morphology were measured. The presented research has shown that comprehensive and planned regulation of selected sections of rivers could lead to the channel stabilization and support the rational use of water resources for different purposes, e.g. power plants, municipal purposes, etc. Moreover, detailed research on channel deformation in selected areas indicated the major role of natural factors (geological structure, the type of sediments delivered to the river, vegetation cover, etc.) in the past and present fluvial processes
Strategy of protection against hazardous channel and hydrological processes in rivers of developed territories and territories with focal development
In 2012-2015, the Makkaveev Research Laboratory of Soil Erosion and Fluvial Processes of MSU, Department of Geography, carried out a research, including analysis of hydrological and channel regimes of the Tom river in the Kuznetsk basin (Kuzbass) and the Katun river up to Uimonsky (the Altai), intra-mountain drainage basins, the survey of floodplains and eroded banks, and modelling of floods occurring in floodplains. As a result, a concept has been developed to improve protection measures against hazardous hydrological and channel processes. More than 200 engineering and organisational events were suggested as part of the concept. Given the dense network of river banks and the high potential damage caused by floods in Kuzbass, the continuous protection of cities, large residential and commercial areas, as well as sections of roads and railways subject to erosion is a priority in the flood control concept. In the case of the Katun river basin, characterized by local development, low population density, and relatively small damage caused by floods, the emphasis is put on organisational measures: prevention, evacuation of people and property, insurance and compensation. Selective engineering structures should, as a matter of priority, reduce the dangerous erosion of river banks and ensure a high level of protection of the territory against floods
XQ-100: A legacy survey of one hundred 3.5 ≲ z ≲ 4.5 quasars observed with VLT/X-shooter
We describe the execution and data reduction of the European Southern Observatory Large Programme "Quasars and their absorption lines: a legacy survey of the high-redshift Universe with VLT/X-shooter" (hereafter "XQ-100"). XQ-100 has produced and made publicly available a homogeneous and high-quality sample of echelle spectra of 100 quasars (QSOs) at redshifts z ≃ 3.5-4.5 observed with full spectral coverage from 315 to 2500 nm at a resolving power ranging from R ̃. 4000 to 7000, depending on wavelength. The median signal-to-noise ratios are 33, 25 and 43, as measured at rest-frame wavelengths 1700, 3000 and 3600 Å, respectively. This paper provides future users of XQ-100 data with the basic statistics of the survey, along with details of target selection, data acquisition and data reduction. The paper accompanies the public release of all data products, including 100 reduced spectra. XQ-100 is the largest spectroscopic survey to date of high-redshift QSOs with simultaneous rest-frame UV/optical coverage, and as such enables a wide range of extragalactic research, from cosmology and galaxy evolution to AGN astrophysics. © 2016 ESO
Big Bang Nucleosynthesis and Particle Dark Matter
We review how our current understanding of the light element synthesis during
the Big Bang Nucleosynthesis era may help shed light on the identity of
particle dark matter.Comment: a mini-review for the NJP special issue on dark matte
The ALMA-ALPINE [CII] survey: The star formation history and the dust emission of star-forming galaxies at 4.5 < z < 6.2
Star-forming galaxies are composed of various types of galaxies. However, the luminosity functions at z & 4-5 suggest that most galaxies have a relatively low stellar mass (log Mstar ∼ 10) and a low dust attenuation (AFUV ∼ 1:0). The physical properties of these objects are quite homogeneous. We used an approach where we combined their rest-frame far-infrared and submillimeter emissions and utilized the universe and the redshift as a spectrograph to increase the amount of information in a collective way. From a subsample of 27 ALMA-detected galaxies at z > 4:5, we built an infrared spectral energy distribution composite template. It was used to fit, with CIGALE, the 105 galaxies (detections and upper limits) in the sample from the far-ultraviolet to the far-infrared. The derived physical parameters provide information to decipher the nature of the dust cycle and of the stellar populations in these galaxies. The derived IR composite template is consistent with the galaxies in the studied sample. A delayed star formation history with τmain = 500 Myr is slightly favored by the statistical analysis as compared to a delayed with a final burst or a continuous star formation history. The position of the sample in the star formation rate (SFR) versus Mstar diagram is consistent with previous papers. The redshift evolution of the log Mstar versus AFUV relation is in agreement with an evolution in redshift of this relation. This evolution is necessary to explain the cosmic evolution of the average dust attenuation of galaxies. Evolution is also observed in the Ldust=LFUV (IRX) versus UV slope βFUV diagram: younger galaxies have bluer βFUV. We modeled the shift of galaxies in the IRX versus the βFUV diagram with the mass-weighted age as a free parameter, and we provide an equation to make predictions. The large sample studied in this paper is generally consistent with models that assume rapid dust formation from supernovae and removal of dust by outflows and supernovae blasts. However, we find that high mass dusty star-forming galaxies cannot be explained by the models
The Circumgalactic Medium in Massive Halos
This chapter presents a review of the current state of knowledge on the cool
(T ~ 1e4 K) halo gas content around massive galaxies at z ~ 0.2-2. Over the
last decade, significant progress has been made in characterizing the cool
circumgalactic gas in massive halos of Mh ~ 1e12-1e14 Msun at intermediate
redshifts using absorption spectroscopy. Systematic studies of halo gas around
massive galaxies beyond the nearby universe are made possible by large
spectroscopic samples of galaxies and quasars in public archives. In addition
to accurate and precise constraints for the incidence of cool gas in massive
halos, detailed characterizations of gas kinematics and chemical compositions
around massive quiescent galaxies at z ~ 0.5 have also been obtained. Combining
all available measurements shows that infalling clouds from external sources
are likely the primary source of cool gas detected at d >~ 100 kpc from massive
quiescent galaxies. The origin of the gas closer in is currently less certain,
but SNe Ia driven winds appear to contribute significantly to cool gas found at
d < 100 kpc. In contrast, cool gas observed at d <~ 200 kpc from luminous
quasars appears to be intimately connected to quasar activities on parsec
scales. The observed strong correlation between cool gas covering fraction in
quasar host halos and quasar bolometric luminosity remains a puzzle. Combining
absorption-line studies with spatially-resolved emission measurements of both
gas and galaxies is the necessary next step to address remaining questions.Comment: 29 pages, 7 figures, invited review to appear in "Gas Accretion onto
Galaxies", Astrophysics and Space Science Library, eds. A. Fox & R. Dave, to
be published by Springe
The [OIII] emission line luminosity function of optically selected type-2 AGN from zCOSMOS
We present a catalog of 213 type-2 AGN selected from the zCOSMOS survey. The
selected sample covers a wide redshift range (0.15<z<0.92) and is deeper than
any other previous study, encompassing the luminosity range 10^{5.5} < Lsun<
L[OIII] < 10^{9.1} Lsun. We explore the intrinsic properties of these AGN and
the relation to their X-ray emission (derived from the XMM-COSMOS
observations). We study their evolution by computing the [OIII]5007A line
luminosity function (LF) and we constrain the fraction of obscured AGN as a
function of luminosity and redshift. The sample was selected on the basis of
the optical emission line ratios, after applying a cut to the signal-to-noise
ratio (S/N) of the relevant lines. We used the standard diagnostic diagrams
[OIII]/Hbeta versus [NII]/Halpha and ([OIII]/Hbeta versus [SII]/Halpha) to
isolate AGN in the redshift range 0.15<z<0.45 and the diagnostic diagram
[OIII]/Hbeta versus [OII]/Hbeta to extend the selection to higher redshift
(0.5<z<0.92). Combining our sample with one drawn from SDSS, we found that the
best description of the evolution of type-2 AGN is a luminosity-dependent
density evolution model. Moreover, using the type-1 AGN LF we were able to
constrain the fraction of type-2 AGN to the total (type-1 + type-2) AGN
population. We found that the type-2 fraction decreases with luminosity, in
agreement with the most recent results, and shows signs of a slight increase
with redshift. However, the trend with luminosity is visible only after
combining the SDSS+zCOSMOS samples. From the COSMOS data points alone, the
type-2 fraction seems to be quite constant with luminosity.Comment: 20 pages, 11 figures, accepted for publication in Astronomy and
Astrophysic
The First Positive Detection of Molecular Gas in a GRB Host Galaxy
We report on strong H2 and CO absorption from gas within the host galaxy of
gamma-ray burst (GRB) 080607. Analysis of our Keck/LRIS afterglow spectrum
reveals a very large HI column density (NHI = 10^22.70 cm^-2) and strong
metal-line absorption at z_GRB = 3.0363 with a roughly solar metallicity. We
detect a series of A-X bandheads from CO and estimate N(CO) = 10^16.5 cm^-2 and
T_ex^CO > 100K. We argue that the high excitation temperature results from UV
pumping of the CO gas by the GRB afterglow. Similarly, we observe H2 absorption
via the Lyman-Werner bands and estimate N(H2) = 10^21.2 cm^-2 with T_ex^H2 =
10--300K. The afterglow photometry suggests an extinction law with R_V=4 and
A_V=3.2 mag and requires the presence of a modest 2175A bump. Additionally,
modeling of the Swift/XRT X-ray spectrum confirms a large column density with
N(H) = 10^22.58 cm^-2. Remarkably, this molecular gas has extinction
properties, metallicity, and a CO/H2 ratio comparable to those of translucent
molecular clouds of the Milky Way, suggesting that star formation at high z
proceeds in similar environments as today. However, the integrated
dust-to-metals ratio is sub-Galactic, suggesting the dust is primarily
associated with the molecular phase while the atomic gas has a much lower
dust-to-gas ratio. Sightlines like GRB 080607 serve as powerful probes of
nucleosynthesis and star-forming regions in the young universe and contribute
to the population of "dark" GRB afterglows.Comment: 6 pages, 4 figures, 1 table. Accepted to ApJL on December 3, 200
ALMA Lensing Cluster Survey: and Photometry of 33 Lensed Fields Built with CHArGE
We present a set of multi-wavelength mosaics and photometric catalogs in the
ALMA lensing cluster survey (ALCS) fields. The catalogs were built by
reprocessing of archival data from the CHArGE compilation, taken by the
() in the RELICS, CLASH and
Hubble Frontier Fields. Additionally we have reconstructed the
IRAC 3.6 and 4.5 m mosaics, by utilising all the
available archival IRSA/SHA exposures. To alleviate the effect of blending in
such a crowded region, we have modelled the photometry by
convolving the detection image with the PSF
using the novel software. The final catalogs contain 218,000
sources, covering a combined area of 690 arcmin. These catalogs will serve
as an important tool in aiding the search of the sub-mm galaxies in future ALMA
surveys, as well as follow ups of the dark - IRAC sources.
Coupled with the available photometry the addition of the 3.6
and 4.5 m bands will allow us to place a better constraint on photometric
redshifts and stellar masses of these objects, thus giving us an opportunity to
identify high-redshift candidates for spectroscopic follow ups and answer the
important questions regarding the epoch of reionization and formation of first
galaxies.Comment: 35 pages, 19 figures, 4 tables. Submitted to ApJS. Mosaics and
photometric catalogs can be accessed online
https://github.com/dawn-cph/alcs-cluster
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