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Reproducing the kinematics of damped Lyman α systems
We examine the kinematic structure of Damped Lyman-alpha Systems (DLAs) in a
series of cosmological hydrodynamic simulations using the AREPO code. We are
able to match the distribution of velocity widths of associated low ionisation
metal absorbers substantially better than earlier work. Our simulations produce
a population of DLAs dominated by halos with virial velocities around 70 km/s,
consistent with a picture of relatively small, faint objects. In addition, we
reproduce the observed correlation between velocity width and metallicity and
the equivalent width distribution of SiII. Some discrepancies of moderate
statistical significance remain; too many of our spectra show absorption
concentrated at the edge of the profile and there are slight differences in the
exact shape of the velocity width distribution. We show that the improvement
over previous work is mostly due to our strong feedback from star formation and
our detailed modelling of the metal ionisation state
Immobilization of catalase via adsorption into natural and modified active carbon obtained from walnut in various methods
In the present work, the immobilization of catalase into natural active carbon and active carbon modified by hydrochloric acid was carried out. In the experimental section, the effects of pH, ionic strength andreaction temperature were chosen as parameters, with experiments performed in batch system. For the optimization of immobilization procedure, values of kinetic parameters were evaluated. It was observedthat storage and operational stabilities of the enzyme increased with immobilization. The results obtained from experiments showed that active carbon is a valuable support for the adsorption of enzymes
Hot Gaseous Coronae around Spiral Galaxies: Probing the Illustris Simulation
The presence of hot gaseous coronae around present-day massive spiral
galaxies is a fundamental prediction of galaxy formation models. However, our
observational knowledge remains scarce, since to date only four gaseous coronae
were detected around spirals with massive stellar bodies
(). To explore the hot coronae around
lower mass spiral galaxies, we utilized Chandra X-ray observations of a sample
of eight normal spiral galaxies with stellar masses of . Although statistically significant diffuse X-ray emission is
not detected beyond the optical radii ( kpc) of the galaxies, we derive
limits on the characteristics of the coronae. These limits,
complemented with previous detections of NGC 1961 and NGC 6753, are used to
probe the Illustris Simulation. The observed upper limits on the
X-ray luminosities and gas masses exceed or are at the upper end of the model
predictions. For NGC 1961 and NGC 6753 the observed gas temperatures, metal
abundances, and electron density profiles broadly agree with those predicted by
Illustris. These results hint that the physics modules of Illustris are broadly
consistent with the observed properties of hot coronae around spiral galaxies.
However, a shortcoming of Illustris is that massive black holes, mostly
residing in giant ellipticals, give rise to powerful radio-mode AGN feedback,
which results in under luminous coronae for ellipticals.Comment: 12 pages, 6 figures, accepted for publication in Ap
Chemical pre-processing of cluster galaxies over the past 10 billion years in the IllustrisTNG simulations
We use the IllustrisTNG simulations to investigate the evolution of the
mass-metallicity relation (MZR) for star-forming cluster galaxies as a function
of the formation history of their cluster host. The simulations predict an
enhancement in the gas-phase metallicities of star-forming cluster galaxies
(10^9< M_star<10^10 M_sun) at z<1.0 in comparisons to field galaxies. This is
qualitatively consistent with observations. We find that the metallicity
enhancement of cluster galaxies appears prior to their infall into the central
cluster potential, indicating for the first time a systematic "chemical
pre-processing" signature for {\it infalling} cluster galaxies. Namely,
galaxies which will fall into a cluster by z=0 show a ~0.05 dex enhancement in
the MZR compared to field galaxies at z<0.5. Based on the inflow rate of gas
into cluster galaxies and its metallicity, we identify that the accretion of
pre-enriched gas is the key driver of the chemical evolution of such galaxies,
particularly in the stellar mass range (10^9< M_star<10^10 M_sun). We see
signatures of an environmental dependence of the ambient/inflowing gas
metallicity which extends well outside the nominal virial radius of clusters.
Our results motivate future observations looking for pre-enrichment signatures
in dense environments.Comment: 5 pages, 4 figures, accepted for publication in MNRAS Letter
Damped lyman α absorbers as a probe of stellar feedback
We examine the abundance, clustering and metallicity of Damped Lyman-alpha
Absorbers (DLAs) in a suite of hydrodynamic cosmological simulations using the
moving mesh code AREPO. We incorporate models of supernova and AGN feedback, as
well as molecular hydrogen formation. We compare our simulations to the column
density distribution function at , the total DLA abundance at , the
measured DLA bias at and the DLA metallicity distribution at .
Our preferred models produce populations of DLAs in good agreement with most of
these observations. The exception is the DLA abundance at , which we
show requires stronger feedback in mass halos.
While the DLA population probes a wide range of halo masses, we find the
cross-section is dominated by halos of mass and virial velocities . The simulated DLA
population has a linear theory bias of , whereas the observations require
. We show that non-linear growth increases the bias in our
simulations to at , the smallest scale observed.
The scale-dependence of the bias is, however, very different in the simulations
compared against the observations. We show that, of the observations we
consider, the DLA abundance and column density function provide the strongest
constraints on the feedback model
Constraint on the Assembly and Dynamics of Galaxies. II. Properties of Kiloparsec-Scale Clumps in Rest-Frame Optical Emission of z ~ 2 Star-Forming Galaxies
We study the properties of luminous stellar "clumps" identified in deep, high-resolution Hubble Space Telescope NIC2/F160W imaging at 1.6 μm of six z ~ 2 star-forming galaxies with existing near-infrared integral field spectroscopy from SINFONI at the Very Large Telescope. Individual clumps contribute ~0.5%-15% of the galaxy-integrated rest-frame ≈5000 Å emission, with median of ≈2%; the total contribution of clump light ranges from 10% to 25%. The median intrinsic clump size and stellar mass are ~1 kpc and ~10^9 M_☉, in the ranges for clumps identified in rest-UV or line emission in other studies. The clump sizes and masses in the subset of disks are broadly consistent with expectations for clump formation through gravitational instabilities in gas-rich, turbulent disks given the host galaxies' global properties. By combining the NIC2 data with Advanced Camera for Surveys (ACS)/F814W imaging available for one source, and adaptive-optics-assisted SINFONI Hα data for another, we infer modest color, M/L, and stellar age variations within each galaxy. In these two objects, sets of clumps identified at different wavelengths do not fully overlap; NIC2-identified clumps tend to be redder/older than ACS- or Hα-identified clumps without rest-frame optical counterparts. There is evidence for a systematic trend of older ages at smaller galactocentric radii among the clumps, consistent with scenarios where inward migration of clumps transports material toward the central regions. From constraints on a bulge-like component at radii ≾1-3 kpc, none of the five disks in our sample appears to contain a compact massive stellar core, and we do not discern a trend of bulge stellar mass fraction with stellar age of the galaxy. Further observations are necessary to probe the buildup of stellar bulges and the role of clumps in this process
Linking galaxy structural properties and star formation activity to black hole activity with IllustrisTNG
We study the connection between active galactic nuclei (AGN) and their host
galaxies through cosmic time in the large-scale cosmological IllustrisTNG
simulations. We first compare BH properties, i.e. the hard X-ray BH luminosity
function, AGN galaxy occupation fraction, and distribution of Eddington ratios,
to available observational constraints. The simulations produce a population of
BHs in good agreement with observations, but we note an excess of faint AGN in
hard X-ray (L_x ~ 10^{43-44} erg/s), and a lower number of bright AGN
(L_x>10^{44} erg/s), a conclusion that varies quantitatively but not
qualitatively with BH luminosity estimation method. The lower Eddington ratios
of the 10^{9} Msun BHs compared to observations suggest that AGN feedback may
be too efficient in this regime. We study galaxy star formation activity and
structural properties, and design sample-dependent criteria to identify
different galaxy types (star-forming/quiescent, extended/compact) that we apply
both to the simulations and observations from the candels fields. We analyze
how the simulated and observed galaxies populate the specific star formation
rate - stellar mass surface density diagram. A large fraction of the z=0
M_{star}>10^{11} Msun quiescent galaxies first experienced a compaction phase
(i.e. reduction of galaxy size) while still forming stars, and then a quenching
event. We measure the dependence of AGN fraction on galaxies' locations in this
diagram. After correcting the simulations with a redshift and AGN
luminosity-dependent model for AGN obscuration, we find good qualitative and
quantitative agreement with observations. The AGN fraction is the highest among
compact star-forming galaxies (16-20% at z~1.5-2), and the lowest among compact
quiescent galaxies (6-10% at z~1.5-2).Comment: 35 pages, 22 figures, accepted for publication in MNRA
A Comparison of Circumgalactic Mg ii Absorption between the TNG50 Simulation and the MEGAFLOW Survey
The circumgalactic medium (CGM) contains information on gas flows around galaxies, such as accretion and supernova-driven winds, which are difficult to constrain from observations alone. Here, we use the high-resolution TNG50 cosmological magnetohydrodynamical simulation to study the properties and kinematics of the CGM around star-forming galaxies in 1011.5-1012 M o˙ halos at z ≃ 1 using mock Mg ii absorption lines, which we generate by postprocessing halos to account for photoionization in the presence of a UV background. We find that the Mg ii gas is a very good tracer of the cold CGM, which is accreting inward at inflow velocities of up to 50 km s-1. For sight lines aligned with the galaxy's major axis, we find that Mg ii absorption lines are kinematically shifted due to the cold CGM's significant corotation at speeds up to 50% of the virial velocity for impact parameters up to 60 kpc. We compare mock Mg ii spectra to observations from the MusE GAs FLow and Wind (MEGAFLOW) survey of strong Mg ii absorbers (EW2796 Å0 > 0.5 Å). After matching the equivalent-width (EW) selection, we find that the mock Mg ii spectra reflect the diversity of observed kinematics and EWs from MEGAFLOW, even though the sight lines probe a very small fraction of the CGM. Mg ii absorption in higher-mass halos is stronger and broader than in lower-mass halos but has qualitatively similar kinematics. The median-specific angular momentum of the Mg ii CGM gas in TNG50 is very similar to that of the entire CGM and only differs from non-CGM components of the halo by normalization factors of ≲1 dex
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