Radionuclides are unstable isotopes that mainly emit alpha (α), beta (β) or gamma (γ) radiation through radiation decay. Therefore, they are used in the biomedical field to label biomolecules or ...drugs for diagnostic imaging applications, such as positron emission tomography (PET) and/or single-photon emission computed tomography (SPECT). A growing field of research is the development of new radiopharmaceuticals for use in cancer treatments. Preclinical studies are the gold standard for translational research. Specifically, in vitro radiopharmaceutical studies are based on the use of radiopharmaceuticals directly on cells. To date, radiometric β- and γ-counters are the only tools able to assess a preclinical in vitro assay with the aim of estimating uptake, retention, and release parameters, including time- and dose-dependent cytotoxicity and kinetic parameters. This review has been designed for researchers, such as biologists and biotechnologists, who would like to approach the radiobiology field and conduct in vitro assays for cellular radioactivity evaluations using radiometric counters. To demonstrate the importance of in vitro radiopharmaceutical assays using radiometric counters with a view to radiogenomics, many studies based on sup.64 Cu-, sup.68 Ga-, sup.125 I-, and sup.99m Tc-labeled radiopharmaceuticals have been revised and summarized in this manuscript.
Radionuclides are unstable isotopes that mainly emit alpha (α), beta (β) or gamma (γ) radiation through radiation decay. Therefore, they are used in the biomedical field to label biomolecules or ...drugs for diagnostic imaging applications, such as positron emission tomography (PET) and/or single-photon emission computed tomography (SPECT). A growing field of research is the development of new radiopharmaceuticals for use in cancer treatments. Preclinical studies are the gold standard for translational research. Specifically, in vitro radiopharmaceutical studies are based on the use of radiopharmaceuticals directly on cells. To date, radiometric β- and γ-counters are the only tools able to assess a preclinical in vitro assay with the aim of estimating uptake, retention, and release parameters, including time- and dose-dependent cytotoxicity and kinetic parameters. This review has been designed for researchers, such as biologists and biotechnologists, who would like to approach the radiobiology field and conduct in vitro assays for cellular radioactivity evaluations using radiometric counters. To demonstrate the importance of in vitro radiopharmaceutical assays using radiometric counters with a view to radiogenomics, many studies based on
Cu-,
Ga-,
I-, and
Tc-labeled radiopharmaceuticals have been revised and summarized in this manuscript.
ABSTRACT We present a sample of 45 Damped Ly system (DLA; ) counterparts (33 detections, 12 upper limits) which host gamma-ray bursts (GRB-DLAs) in order to investigate star formation and metallicity ...within galaxies hosting DLAs. Our sample spans and is nearly three times larger than any previously detected DLA counterparts survey based on quasar line-of-sight searches (QSO-DLAs). We report star formation rates (SFRs) from rest-frame UV photometry and spectral energy distribution modeling. We find that DLA counterpart SFRs are not correlated with either redshift or H i column density. Thanks to the combination of Hubble Space Telescope and ground-based observations, we also investigate DLA host star formation efficiency. Our GRB-DLA counterpart sample spans both higher efficiency and low efficiency star formation regions compared to the local Kennicutt-Schmidt relation, local star formation laws, and cosmological simulations. We also compare the depletion times of our DLA hosts sample to other objects in the local universe; our sample appears to deviate from the star formation efficiencies measured in local spiral and dwarf galaxies. Furthermore, we find similar efficiencies as local inner disks, SMC, and Lyman-break galaxy outskirts. Finally, our enrichment time measurements show a spread of systems with under- and over-abundance of metals, which may suggest that these systems had episodic star formation and a metal enrichment/depletion as a result of strong stellar feedback and/or metal inflow/outflow.
We present a study of the evolution of several classes of Mgii absorbers, and their corresponding Feii absorption, over a large fraction of cosmic history: 2.3-8.7Gyr from the big bang. Our sample ...consists of 87 strong (Å) Mgii absorbers, with redshifts 0.2 < z < 2.5, measured in 81 quasar spectra obtained from the Very Large Telescope/Ultraviolet and Visual Echelle Spectrograph archives of high-resolution spectra (R 45000). No evolutionary trend in is found for moderately strong Mgii absorbers (Å). However, at lower redshifts we find an absence of very strong Mgii absorbers (those with Å) with small ratios of equivalent widths of Feii to Mgii. At high redshifts, very strong Mgii absorbers with both small and large values are present. We compare our findings to a sample of 100 weak Mgii absorbers (Å) found in the same quasar spectra by Narayanan et al. The main effect driving the evolution of very strong Mgii systems is the difference between the kinematic profiles at low and high redshift. At high redshift, we observe that, among the very strong Mgii absorbers, all of the systems with small ratios of have relatively large velocity spreads, resulting in less saturated profiles. At low redshift, such kinematically spread systems are absent, and both Feii and Mgii are saturated, leading to values that are all close to 1. The high redshift, small systems could correspond to sub-damped Lyman alpha systems, many of which have large velocity spreads and are possibly linked to superwinds in star-forming galaxies. In addition to the change in saturation due to kinematic evolution, the smaller values could be due to a lower abundance of Fe at high redshifts, which would indicate relatively early stages of star formation in those environments. PUBLICATION ABSTRACT
Evolution of the population of very strong Mg II absorbers Rodríguez Hidalgo, Paola; Wessels, Kaylan; Charlton, Jane C ...
Monthly notices of the Royal Astronomical Society,
11 December 2012, Letnik:
427, Številka:
3
Journal Article
Recenzirano
Odprti dostop
Abstract
We present a study of the evolution of several classes of Mg ii absorbers, and their corresponding Fe ii absorption, over a large fraction of cosmic history: 2.3-8.7 Gyr from the big bang. ...Our sample consists of 87 strong ( Å) Mg ii absorbers, with redshifts 0.2 < z < 2.5, measured in 81 quasar spectra obtained from the Very Large Telescope/Ultraviolet and Visual Echelle Spectrograph archives of high-resolution spectra (R ∼ 45 000). No evolutionary trend in is found for moderately strong Mg ii absorbers ( Å). However, at lower redshifts we find an absence of very strong Mg ii absorbers (those with Å) with small ratios of equivalent widths of Fe ii to Mg ii. At high redshifts, very strong Mg ii absorbers with both small and large values are present. We compare our findings to a sample of 100 weak Mg ii absorbers ( Å) found in the same quasar spectra by Narayanan et al.
The main effect driving the evolution of very strong Mg ii systems is the difference between the kinematic profiles at low and high redshift. At high redshift, we observe that, among the very strong Mg ii absorbers, all of the systems with small ratios of Wr(Fe II)/Wr(Mg II) have relatively large velocity spreads, resulting in less saturated profiles. At low redshift, such kinematically spread systems are absent, and both Fe ii and Mg ii are saturated, leading to Wr(Fe II)/Wr(Mg II) values that are all close to 1. The high redshift, small Wr(Fe II)/Wr(Mg II) systems could correspond to sub-damped Lyman α systems, many of which have large velocity spreads and are possibly linked to superwinds in star-forming galaxies. In addition to the change in saturation due to kinematic evolution, the smaller Wr(Fe II)/Wr(Mg II) values could be due to a lower abundance of Fe at high redshifts, which would indicate relatively early stages of star formation in those environments.
KA1858+4850 is a narrow-line Seyfert 1 galaxy at redshift 0.078 and is among the brightest active galaxies monitored by the Kepler mission. We have carried out a reverberation mapping campaign ...designed to measure the broad-line region size and estimate the mass of the black hole in this galaxy. We obtained 74 epochs of spectroscopic data using the Kast Spectrograph at the Lick 3 m telescope from 2012 February to November, and obtained complementary V-band images from five other ground-based telescopes. We measured the H beta light curve lag with respect to the V-band continuum light curve using both cross-correlation techniques (CCF) and continuum light curve variability modeling with the JAVELIN method and found rest-frame lags of tau sub(CCF) = 13.53 super(+2.03) sub(-2.32) days and tau sub(JAVELIN) = 13.15 super(+1.08) sub(-1.00) days. The H beta rms line profile has a width of sigma sub(line) = 770 + or - 49 km s super(-1). Combining these two results and assuming a virial scale factor of f = 5.13, we obtained a virial estimate of M sub(BH) = 8.06 super(+1.59) sub(-2.32) x 10 super(6) M sub(middot in circle) or the mass of the central black hole and an Eddington ratio of L/L sub(Edd) approximately 0.2. We also obtained consistent but slightly shorter emission-line lags with respect to the Kepler light curve. Thanks to the Kepler mission, the light curve of KA 1858+4850 has among the highest cadences and signal-to-noise ratios ever measured for an active galactic nucleus; thus, our black hole mass measurement will serve as a reference point for relations between black hole mass and continuum variability characteristics in active galactic nuclei.
ABSTRACT The Fermi Gamma-ray Space Telescope has greatly expanded the number and energy window of observations of gamma-ray bursts (GRBs). However, the coarse localizations of tens to a hundred ...square degrees provided by the Fermi GRB Monitor instrument have posed a formidable obstacle to locating the bursts' host galaxies, measuring their redshifts, and tracking their panchromatic afterglows. We have built a target-of-opportunity mode for the intermediate Palomar Transient Factory in order to perform targeted searches for Fermi afterglows. Here, we present the results of one year of this program: 8 afterglow discoveries out of 35 searches. Two of the bursts with detected afterglows (GRBs 130702A and 140606B) were at low redshift (z = 0.145 and 0.384, respectively) and had spectroscopically confirmed broad-line Type Ic supernovae. We present our broadband follow-up including spectroscopy as well as X-ray, UV, optical, millimeter, and radio observations. We study possible selection effects in the context of the total Fermi and Swift GRB samples. We identify one new outlier on the Amati relation. We find that two bursts are consistent with a mildly relativistic shock breaking out from the progenitor star rather than the ultra-relativistic internal shock mechanism that powers standard cosmological bursts. Finally, in the context of the Zwicky Transient Facility, we discuss how we will continue to expand this effort to find optical counterparts of binary neutron star mergers that may soon be detected by Advanced LIGO and Virgo.
Very early observations with the Swift satellite of g-ray burst (GRB) afterglows reveal that the optical component is not detected in a large number of cases. This is in contrast to the bright ...optical flashes previously discovered in some GRBs (e.g., GRB 990123 and GRB 021211). Comparisons of the X-ray afterglow flux to the optical afterglow flux and prompt g-ray fluence is used to quantify the seemingly deficient optical, and in some cases X-ray, light at these early epochs. This comparison reveals that some of these bursts appear to have higher than normal g-ray efficiencies. We discuss possible mechanisms and their feasibility for explaining the apparent lack of early optical emission. The mechanisms considered include, foreground extinction, circumburst absorption, Lya blanketing and absorption due to high-redshift, low-density environments, rapid temporal decay, and intrinsic weakness of the reverse shock. Of these, foreground extinction, circumburst absorption, and high redshift provide the best explanations for most of the nondetections in our sample. There is tentative evidence of suppression of the strong reverse shock emission. This could be because of a Poynting flux-dominated flow or a pure nonrelativistic hydrodynamic reverse shock.
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