The chemical composition of gas in galaxies can be measured in great detail using absorption spectroscopy. By studying gas in galaxies in this way, it is possible to investigate small and faint ...galaxies, which are the most numerous in the universe. In particular, the chemical distribution of gas in absorbing systems gives us insight into cycles of gas in and around galaxies. In this work we study chemical enrichment within 64 damped Lyman-α absorption systems (DLAs) for redshifts in the range 1.7 < z < 4.2. We use high-resolution spectra from VLT/UVES to infer dust depletion from relative abundances of several metals. Specifically, we performed a component-by-component analysis within DLAs, and characterised variations in their chemical enrichment. Unlike hydrogen, the metal columns can be characterised according to their individual components. We used them to derive the dust depletion, which is an indicator of chemical enrichment. Our main results are as follows. Firstly, we find that some DLAs are chemically diverse within themselves (with the measure of dust depletion Zn/Fefit ranging up to 0.62 dex within a single system), suggesting that the absorbing gas within these galaxies is chemically diverse. Secondly, although we do not find a clear trend of decreasing dust depletion with redshift, we do see that the most chemically enriched systems are at lower redshifts. We also observe evidence for dust-poor components at all redshifts, which may be due to the accretion of pristine gas onto galaxies. By combining the chemical and kinematic properties of the individual gas components, we observe potential signatures of infalling gas with low depletion at velocities below ∼100 km s−1, and outflows with high depletion and velocities of ∼600 km s−1. Finally, we find over-abundances of α-elements (an enhancement of ∼0.3 dex) and under-abundances of Mn in several gas components, which is likely a signature of core-collapse supernovae nucleosythesis in the ISM. We observe these effects mostly at lower levels of chemical enrichment.
The cosmic buildup of dust and metals Heintz, K E; De Cia, A; Thöne, C C ...
Astronomy and astrophysics (Berlin),
11/2023, Volume:
679
Journal Article
Peer reviewed
Open access
The chemical enrichment of dust and metals in the interstellar medium of galaxies throughout cosmic time is one of the key driving processes of galaxy evolution. Here we study the evolution of the ...gas-phase metallicities, dust-to-gas (DTG) ratios, and dust-to-metal (DTM) ratios of 36 star-forming galaxies at 1.7 < z < 6.3 probed by gamma-ray bursts (GRBs). We compiled all GRB-selected galaxies with intermediate- (ℛ = 7000) to high-resolution (ℛ > 40 000) spectroscopic data, including three new sources, for which at least one refractory (e.g., Fe) and one volatile (e.g., S or Zn) element have been detected at S/N > 3. This is to ensure that accurate abundances and dust depletion patterns can be obtained. We first derived the redshift evolution of the dust-corrected, absorption-line-based gas-phase metallicity, M/Htot, in these galaxies, for which we determine a linear relation with redshift M/Htot(z) = (−0.21 ± 0.04)z − (0.47 ± 0.14). We then examined the DTG and DTM ratios as a function of redshift and through three orders of magnitude in metallicity, quantifying the relative dust abundance both through the direct line-of-sight visual extinction, AV, and the derived depletion level. We used a novel method to derive the DTG and DTM mass ratios for each GRB sightline, summing up the mass of all the depleted elements in the dust phase. We find that the DTG and DTM mass ratios are both strongly correlated with the gas-phase metallicity and show a mild evolution with redshift as well. While these results are subject to a variety of caveats related to the physical environments and the narrow pencil-beam sightlines through the interstellar medium probed by the GRBs, they provide strong implications for studies of dust masses that aim to infer the gas and metal content of high-redshift galaxies, and particularly demonstrate the large offset from the average Galactic value in the low-metallicity, high-redshift regime.
Here we explore the efficiency and fidelity of a purely astrometric selection of quasars as point sources with zero proper motions in the
Gaia
data release 2 (DR2). We have built a complete candidate ...sample including 104
Gaia
-DR2 point sources, which are brighter than 20th magnitude in the
Gaia G
-band within one degree of the north Galactic pole (NGP); all of them have proper motions that are consistent with zero within 2
σ
uncertainty. In addition to pre-existing spectra, we have secured long-slit spectroscopy of all the remaining candidates and find that all 104 stationary point sources in the field can be classified as either quasars (63) or stars (41). One of the new quasars that we discover is particularly interesting as the line-of-sight to it passes through the disc of a foreground (
z
= 0.022) galaxy, which imprints both Na
D
absorption and dust extinction on the quasar spectrum. The selection efficiency of the zero-proper-motion criterion at high Galactic latitudes is thus ≈60%. Based on this complete quasar sample, we examine the basic properties of the underlying quasar population within the imposed limiting magnitude. We find that the surface density of quasars is 20 deg
−2
(at
G
< 20 mag), the redshift distribution peaks at
z
∼ 1.5, and only eight systems (13
-3
+5
%) show significant dust reddening. We then explore the selection efficiency of commonly used optical, near-, and mid-infrared quasar identification techniques and find that they are all complete at the 85−90% level compared to the astrometric selection. Finally, we discuss how the astrometric selection can be improved to an efficiency of ≈70% by including an additional cut requiring parallaxes of the candidates to be consistent with zero within 2
σ
. The selection efficiency will further increase with the release of future, more sensitive astrometric measurements from the
Gaia
mission. This type of selection, which is purely based on the astrometry of the quasar candidates, is unbiased in terms of colours and intrinsic emission mechanisms of the quasars and thus provides the most complete census of the quasar population within the limiting magnitude of
Gaia
.
The chemical composition of gas in galaxies can be measured in great detail using absorption spectroscopy. By studying gas in galaxies in this way, it is possible to investigate small and faint ...galaxies, which are the most numerous in the universe. In particular, the chemical distribution of gas in absorbing systems gives us insight into cycles of gas in and around galaxies. In this work we study chemical enrichment within 64 damped Lyman-
α
absorption systems (DLAs) for redshifts in the range 1.7 <
z
< 4.2. We use high-resolution spectra from VLT/UVES to infer dust depletion from relative abundances of several metals. Specifically, we performed a component-by-component analysis within DLAs, and characterised variations in their chemical enrichment. Unlike hydrogen, the metal columns can be characterised according to their individual components. We used them to derive the dust depletion, which is an indicator of chemical enrichment. Our main results are as follows. Firstly, we find that some DLAs are chemically diverse within themselves (with the measure of dust depletion Zn/Fe
fit
ranging up to 0.62 dex within a single system), suggesting that the absorbing gas within these galaxies is chemically diverse. Secondly, although we do not find a clear trend of decreasing dust depletion with redshift, we do see that the most chemically enriched systems are at lower redshifts. We also observe evidence for dust-poor components at all redshifts, which may be due to the accretion of pristine gas onto galaxies. By combining the chemical and kinematic properties of the individual gas components, we observe potential signatures of infalling gas with low depletion at velocities below ∼100 km s
−1
, and outflows with high depletion and velocities of ∼600 km s
−1
. Finally, we find over-abundances of
α
-elements (an enhancement of ∼0.3 dex) and under-abundances of Mn in several gas components, which is likely a signature of core-collapse supernovae nucleosythesis in the ISM. We observe these effects mostly at lower levels of chemical enrichment.
ABSTRACT
Among active galactic nuclei, blazars show extreme variability properties. We here investigate the case of the BL Lac object S4 0954+65 with data acquired in 2019–2020 by the Transiting ...Exoplanet Survey Satellite (TESS) and by the Whole Earth Blazar Telescope (WEBT) Collaboration. The 2-min cadence optical light curves provided by TESS during three observing sectors of nearly 1 month each allow us to study the fast variability in great detail. We identify several characteristic short-term time-scales, ranging from a few hours to a few days. However, these are not persistent, as they differ in the various TESS sectors. The long-term photometric and polarimetric optical and radio monitoring undertaken by the WEBT brings significant additional information, revealing that (i) in the optical, long-term flux changes are almost achromatic, while the short-term ones are strongly chromatic; (ii) the radio flux variations at 37 GHz follow those in the optical with a delay of about 3 weeks; (iii) the range of variation of the polarization degree and angle is much larger in the optical than in the radio band, but the mean polarization angles are similar; (iv) the optical long-term variability is characterized by a quasi-periodicity of about 1 month. We explain the source behaviour in terms of a rotating inhomogeneous helical jet, whose pitch angle can change in time.
The study of the properties of galaxies in the first billion years after the Big Bang is one of the major topics of current astrophysics. Optical and near-infrared spectroscopy of the afterglows of ...long gamma-ray bursts (GRBs) provides a powerful diagnostic tool to probe the interstellar medium (ISM) of their host galaxies and foreground absorbers, even up to the highest redshifts. We analyze the VLT/X-shooter afterglow spectrum of GRB 210905A, triggered by the
Neil Gehrels Swift
Observatory, and detect neutral hydrogen, low-ionization, high-ionization, and fine-structure absorption lines from a complex system at
z
= 6.3118, which we associate with the GRB host galaxy. We use them to study the ISM properties of the host system, revealing the metallicity, kinematics, and chemical abundance pattern of its gas along the GRB line of sight. We also detect absorption lines from at least two foreground absorbers at
z
= 5.7390 and
z
= 2.8296. The total metallicity of the
z
∼ 6.3 system is M/H
tot
= −1.72 ± 0.13, after correcting for dust depletion and taking
α
-element enhancement into account, as suggested by our analysis. This is consistent with the values found for the other two GRBs at
z
∼ 6 with spectroscopic data showing metal absorption lines (GRB 050904 and GRB 130606A), and it is at the higher end of the metallicity distribution of quasar damped Lyman-
α
systems (QSO-DLAs) extrapolated to such a high redshift. In addition, we determine the overall amount of dust and dust-to-metal mass ratio (DTM) (Zn/Fe
fit
= 0.33 ± 0.09 and DTM = 0.18 ± 0.03). We find indications of nucleosynthesis due to massive stars and, for some of the components of the gas clouds, we find evidence of peculiar nucleosynthesis, with an overabundance of aluminum (as also found for GRB 130606A). From the analysis of fine-structure lines, we determine distances of several kiloparsecs for the low-ionization gas clouds closest to the GRB. Those are farther distances than usually found for GRB host absorption systems, possibly due to the very high number of ionizing photons produced by the GRB that could ionize the line of sight up to several hundreds of parsecs. Using the HST/
F
140
W
image of the GRB field, we show the GRB host galaxy (with a possible afterglow contamination) as well as multiple objects within 2″ from the GRB position. We discuss the galaxy structure and kinematics that could explain our observations, also taking into account a tentative detection of Lyman-
α
emission at
z
= 6.3449 (∼1200 km s
−1
from the GRB redshift in velocity space), and the observational properties of Lyman-
α
emitters at very high redshift. This study shows the amazing potential of GRBs to access detailed information on the properties (metal enrichment, gas kinematic, dust content, nucleosynthesis...) of very high-redshift galaxies, independently of the galaxy luminosity. Deep spectroscopic observations with VLT/MUSE and JWST will offer the unique possibility of combining the information presented in this paper with the properties of the ionized gas, with the goal of better understanding how galaxies in the reionization era form and evolve.
The cosmic buildup of dust and metals Heintz, K. E.; De Cia, A.; Thöne, C. C. ...
Astronomy and astrophysics (Berlin),
11/2023, Volume:
679
Journal Article
Peer reviewed
The chemical enrichment of dust and metals in the interstellar medium of galaxies throughout cosmic time is one of the key driving processes of galaxy evolution. Here we study the evolution of the ...gas-phase metallicities, dust-to-gas (DTG) ratios, and dust-to-metal (DTM) ratios of 36 star-forming galaxies at 1.7 <
z
< 6.3 probed by gamma-ray bursts (GRBs). We compiled all GRB-selected galaxies with intermediate- (ℛ = 7000) to high-resolution (ℛ > 40 000) spectroscopic data, including three new sources, for which at least one refractory (e.g., Fe) and one volatile (e.g., S or Zn) element have been detected at
S
/
N
> 3. This is to ensure that accurate abundances and dust depletion patterns can be obtained. We first derived the redshift evolution of the dust-corrected, absorption-line-based gas-phase metallicity, M/H
tot
, in these galaxies, for which we determine a linear relation with redshift M/H
tot
(
z
) = (−0.21 ± 0.04)
z
− (0.47 ± 0.14). We then examined the DTG and DTM ratios as a function of redshift and through three orders of magnitude in metallicity, quantifying the relative dust abundance both through the direct line-of-sight visual extinction,
A
V
, and the derived depletion level. We used a novel method to derive the DTG and DTM mass ratios for each GRB sightline, summing up the mass of all the depleted elements in the dust phase. We find that the DTG and DTM mass ratios are both strongly correlated with the gas-phase metallicity and show a mild evolution with redshift as well. While these results are subject to a variety of caveats related to the physical environments and the narrow pencil-beam sightlines through the interstellar medium probed by the GRBs, they provide strong implications for studies of dust masses that aim to infer the gas and metal content of high-redshift galaxies, and particularly demonstrate the large offset from the average Galactic value in the low-metallicity, high-redshift regime.
The chemical enrichment of dust and metals in the interstellar medium (ISM) of galaxies throughout cosmic time is one of the key driving processes of galaxy evolution. Here we study the evolution of ...the gas-phase metallicities, dust-to-gas (DTG), and dust-to-metal (DTM) ratios of 36 star-forming galaxies at $1.7 < z < 6.3$ probed by gamma-ray bursts (GRBs). We compile all GRB-selected galaxies with intermediate (R=7000) to high (R>40,000) resolution spectroscopic data for which at least one refractory (e.g. Fe) and one volatile (e.g. S or Zn) element have been detected at S/N>3. This is to ensure that accurate abundances and dust depletion patterns can be obtained. We first derive the redshift evolution of the dust-corrected, absorption-line based gas-phase metallicity M/H$_{\rm tot}$ in these galaxies, for which we determine a linear relation with redshift ${\rm M/H_{tot}}(z) = (-0.21\pm 0.04)z -(0.47\pm 0.14)$. We then examine the DTG and DTM ratios as a function of redshift and through three orders of magnitude in metallicity, quantifying the relative dust abundance both through the direct line-of-sight visual extinction $A_V$ and the derived depletion level. We use a novel method to derive the DTG and DTM mass ratios for each GRB sightline, summing up the mass of all the depleted elements in the dust-phase. We find that the DTG and DTM mass ratios are both strongly correlated with the gas-phase metallicity and show a mild evolution with redshift as well. While these results are subject to a variety of caveats related to the physical environments and the narrow pencil-beam sightlines through the ISM probed by the GRBs, they provide strong implications for studies of dust masses to infer the gas and metal content of high-redshift galaxies, and particularly demonstrate the large offset from the average Galactic value in the low-metallicity, high-redshift regime.
Thorium removal by different adsorbents Metaxas, Michail; Kasselouri-Rigopoulou, Vasilia; Galiatsatou, Polymnia ...
Journal of hazardous materials,
02/2003, Volume:
97, Issue:
1
Journal Article
Peer reviewed
The removal of radiotoxic Th
4+ from aqueous solutions has been explored using two different groups of adsorptive materials (e.g. two activated carbons and four zeolites—two natural and two ...synthetic). The activated carbons were prepared from solvent extracted olive pulp (SEOP) and olive stone (OS) by a two-step physical activation method with steam. They were characterized by N
2 at 77
K adsorption, Hg porosimetry and by determination of their iodine number. All carbons prepared are of the H-type (e.g. contain mainly basic surface oxides) confirmed by the results of the Boehm’s method
. The natural zeolites, clinoptilolite (NaCLI) and mordenite (NaMOR), were pretreated with Na
+ before the adsorption experiments, while the synthetic ones, NaX and NaA, were provided in their commercial sodium form.
The natural zeolites, NaCLI and NaMOR, utilized 11.5 and 38.6% of the theoretical ion-exchange capacity, based on Al content, respectively, while NaX and NaA utilized 41.5 and 45.9%, respectively. The activated carbons showed better removal capability than NaCLI. NaMOR, showed comparable results to the carbon originated from OS, but lower removal capability than the carbon originated from SEOP. The synthetic zeolites showed the highest removal ability for thorium ions due to their increased ion-exchange capacity because of their cleaner and larger framework channels and their higher number of ion-exchange sites. The carbons adsorption capacity mainly depends on the content and nature of functional surface groups. The adsorption data were fitted to Langmuir and Freundlich models. The former achieved best fits and was further applied to obtain the respective Langmuir constant and maximum adsorption capacity for each system.
The chemical composition of gas in galaxies can be measured in detail from absorption spectroscopy. By studying gas in galaxies in this way, it is possible to investigate the small and faint ...galaxies, which are the most numerous in the universe. In particular, the chemical distribution of gas in absorbing systems gives us insight into cycles of gas in and around galaxies. Here we study chemical enrichment within 64 Damped Lyman-alpha Absorption (DLA) systems between \(1.7 < z < 4.2\). We use high-resolution spectra from VLT/UVES to infer dust depletion from relative abundances of several metals. We perform a component-by-component analysis within DLAs, and characterise variations in their chemical enrichment. Unlike hydrogen, the metal columns can be characterised for individual components. We use them to derive the dust depletion (Zn/Fefit), as an indicator for chemical enrichment. We find that some DLAs are chemically diverse within themselves, with Zn/Fefit ranging up to 0.62 dex within a single system. This suggests that absorbing gas within these galaxies is chemically diverse. Although we do not find a clear trend of decreasing dust depletion with redshift, we do see that the most chemically enriched systems are at lower redshifts. We also observe evidence for dust-poor components at all redshifts, which may be due to the accretion of pristine gas onto galaxies. We combine the chemical and kinematic properties of the individual gas components and observe potential signatures of infalling gas, with low depletion at velocities below \(\sim\)100km/s, and outflows, with high depletion and velocities of \(\sim\)600km/s. We find over-abundances of alpha-elements (an enhancement of \(\sim\)0.3dex) and under-abundances of Mn in several components, which is likely a signature of core-collapse SNe nucleosythesis in the ISM. We observe these effects mostly at lower levels of chemical enrichment.
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