Nuclear rings are excellent laboratories for studying intense star formation. We present results from a study of nuclear star-forming rings in five nearby normal galaxies from the Star Formation in ...Radio Survey (SFRS) and four local LIRGs from the Great Observatories All-sky LIRG Survey (GOALS) at sub-kpc resolutions using VLA high-frequency radio continuum observations. We find that nuclear ring star formation (NRSF) contributes 49 - 60\% of the total star formation of the LIRGs, compared to 7 - 40\% for the normal galaxies. We characterize a total of 58 individual star-forming regions in these rings, and find that with measured sizes of 10 - 200 pc, NRSF regions in the LIRGs have SFR and \(\Sigma_\mathrm{SFR}\) up to 1.7 M\(_\odot\)yr\(^{-1}\) and 402 M\(_\odot\)yr\(^{-1}\)kpc\(^{-2}\), respectively, which are about 10 times higher than NRSF regions in the normal galaxies with similar sizes, and comparable to lensed high-\(z\) star-forming regions. At \(\sim 100 - 300\) pc scales, we estimate low contributions (\(< 50\%\)) of thermal free-free emission to total radio continuum emission at 33 GHz in the NRSF regions in the LIRGs, but large variations possibly exist at smaller physical scales. Finally, using archival sub-kpc resolution CO (J=1-0) data of nuclear rings in the normal galaxies and NGC 7469 (LIRG), we find a large scatter in gas depletion times at similar molecular gas surface densities, which tentatively points to a multi-modal star formation relation on sub-kpc scales.
We present results of our analysis of NuSTAR data of the luminous infrared galaxy Mrk 266, which contains two nuclei, SW and NE, resolved in previous Chandra imaging. Combining with the Chandra data, ...we intepret the hard X-ray spectrum obtained from a NuSTAR observation as resulting from steeply rising flux from a Compton-thick AGN in the SW nucleus which is very faint in the Chandra band, confirming the previous claim of Mazzarella et al. (2012). This hard X-ray component is dominated by reflection, and its intrinsic 2-10 keV luminosity is likely to be ~1e43 erg/s. Although it is bright in soft X-ray, only moderately absorbed NE nucleus has a 2-10 keV luminosity of 4e41 erg/s, placing it in the low-luminosity AGN class. These results have implications for understanding the detectability and duty cycles of emission from dual AGN in heavily obscured mergers.
We analyze Chandra X-ray observatory data for a sample of 63 luminous infrared galaxies (LIRGs), sampling the lower-infrared luminosity range of the Great Observatories All-Sky LIRG survey (GOALS), ...which includes the most luminous infrared selected galaxies in the local universe. X-rays are detected for 84 individual galaxies within the 63 systems, for which arcsecond resolution X-ray images, fluxes, infrared and X-ray luminosities, spectra and radial profiles are presented. Using X-ray and MIR selection criteria, we find AGN in (31\(\pm\)5)% of the galaxy sample, compared to the (38\(\pm\)6)% previously found for GOALS galaxies with higher infrared luminosities (C-GOALS I). Using mid-infrared data, we find that (59\(\pm\)9)% of the X-ray selected AGN in the full C-GOALS sample do not contribute significantly to the bolometric luminosity of the host galaxy. Dual AGN are detected in two systems, implying a dual AGN fraction in systems that contain at least one AGN of (29\(\pm\)14)%, compared to the (11\(\pm\)10)% found for the C-GOALS I sample. Through analysis of radial profiles, we derive that most sources, and almost all AGN, in the sample are compact, with half of the soft X-ray emission generated within the inner \(\sim 1\) kpc. For most galaxies, the soft X-ray sizes of the sources are comparable to those of the MIR emission. We also find that the hard X-ray faintness previously reported for the bright C-GOALS I sources is also observed in the brightest LIRGs within the sample, with \(L_{\rm FIR}>8\times10^{10}\) L\(_{\odot}\).
We present the multi-epoch analysis of 13 variable, nearby (z<0.1), Compton-thin (22<logN_H<24) active galactic nuclei (AGN) selected from the 105-month BAT catalog. Analyzing all available archival ...soft and hard X-ray observations, we investigate the line-of-sight hydrogen column density (N_H) variability on timescales ranging from a few days to approximately 20 years. Each source is analyzed by simultaneously modeling the data with three physical torus models, providing tight constraints on torus properties, including the covering factor, the cloud dispersion, and the torus average hydrogen column density (N_H,av). For each epoch, we measure the N_H and categorize the source as `N_H Variable', `Non-variable in N_H', or `Undetermined' based on the degree of variability. Our final sample includes 27 variable, Compton-thin AGN after implementing another 14 AGN analyzed in our previous work. We find that all sources require either flux or N_H variability. We classify 37% of them as `N_H Variable', 44% as `Non-variable in N_H', and 19% as `Undetermined'. Noticeably, there is no discernible difference between geometrical and intrinsic properties among the three variability classes, suggesting no intrinsic differences between the N_H-variable and non-variable sources. We measure the median variation in N_H between any observation pair of the same source to be 25% with respect to the lowest N_H measure in the pair. Furthermore, 48% of the analyzed sources require the inclusion of a Compton-thick reflector in the spectral fitting. Among these, the 30% exhibits recorded 22 GHz water megamaser emission, suggesting a potential shared nature between the two structures.
BL Lacertae (BL Lac) objects are a subclass of blazar, distinguished by their featureless optical spectrum. The featureless spectrum presents a challenge in measuring the redshift of the BL Lacs. In ...this paper, we measure the redshift of BL Lacs using the photometric dropout technique. The space-based telescope \emph{Swift} and the ground-based SARA telescopes are employed to provide magnitudes in the \(uvw2,\ uvm2,\ uvw1,\ u,\ b,\ v,\ g',\ r',\ i',\ z'\) filters. We observe 60 BL Lacs and report reliable redshift upper limits for 41 of them. We discover three new high-\(z\) BL Lacs (\(z>1.3\)) at \(1.74_{-0.08}^{+0.05}\), \(1.88_{-0.03}^{+0.07}\), and \(2.10_{-0.04}^{+0.03}\), bringing the number of high-\(z\) BL Lacs found by this method up to 19. Discussions are made on the implications for the blazar sequence, the \emph{Fermi} blazar divide, and the gamma-ray horizon based on an analysis of the 4LAC catalog and all high-\(z\) BL Lacs found with the photo-\(z\) technique.
The merger of two or more galaxies can enhance the inflow of material from galactic scales into the close environments of Active Galactic Nuclei (AGN), obscuring and feeding the supermassive black ...hole (SMBH). Both recent simulations and observations of AGN in mergers have confirmed that mergers are related to strong nuclear obscuration. However, it is still unclear how AGN obscuration evolves in the last phases of the merger process. We study a sample of 60 Luminous and Ultra-luminous IR galaxies (U/LIRGs) from the GOALS sample observed by NuSTAR. We find that the fraction of AGN that are Compton-thick (CT; \(N_{\rm H}\geq 10^{24}\rm\,cm^{-2}\)) peaks at \(74_{-19}^{+14}\%\) at a late merger stage, prior to coalescence, when the nuclei have projected separations of \(d_{\rm sep}\sim 0.4-6\) kpc. A similar peak is also observed in the median \(N_{\rm H}\) \((1.6\pm0.5)\times10^{24}\rm\,cm^{-2}\). The vast majority (\(85^{+7}_{-9}\%\)) of the AGN in the final merger stages (\(d_{\rm sep}\lesssim 10\) kpc) are heavily obscured (\(N_{\rm H}\geq 10^{23}\rm\,cm^{-2}\)), and the median \(N_{\rm H}\) of the accreting SMBHs in our sample is systematically higher than that of local hard X-ray selected AGN, regardless of the merger stage. This implies that these objects have very obscured nuclear environments, with the \(N_{\rm H}\geq 10^{23}\rm\,cm^{-2}\) gas almost completely covering the AGN in late mergers. CT AGN tend to have systematically higher absorption-corrected X-ray luminosities than less obscured sources. This could either be due to an evolutionary effect, with more obscured sources accreting more rapidly because they have more gas available in their surroundings, or to a selection bias. The latter scenario would imply that we are still missing a large fraction of heavily obscured, lower luminosity (\(L_{2-10}\lesssim 10^{43}\rm\,erg\,s^{-1}\)) AGN in U/LIRGs.
Mrk501 is a very high-energy (VHE) gamma-ray blazar located at z=0.034. During a period of two weeks in July 2014, the highest X-ray activity of Mrk501 was observed in ~14 years of operation of the ...Neil Gehrels Swift Gamma-ray Burst Observatory. We characterize the broadband variability of Mrk501 from radio to VHE gamma rays, and evaluate whether it can be interpreted within theoretical scenarios widely used to explain the broadband emission from blazars. The temporal evolution of the most prominent and variable segments of the SED is described with a one-zone synchrotron self-Compton model with variations in the break energy of the electron energy distribution (EED), and with some adjustments in the magnetic field strength and spectral shape of the EED. A narrow feature at ~3 TeV was observed in the VHE spectrum measured on 2014 July 19 (MJD 56857.98), which is the day with the highest X-ray flux (\(>0.3\) keV) measured during the entire Swift mission. This feature is inconsistent with the classical analytic functions to describe the measured VHE spectra (power law, log-parabola, and log-parabola with exponential cutoff) at more than 3\(\sigma\). A fit with a log-parabola plus a narrow component is preferred over the fit with a single log-parabola at more than 4\(\sigma\), and a dedicated Monte Carlo simulation estimated the significance of this extra component to be larger than 3\(\sigma\). Under the assumption that this VHE spectral feature is real, we show that it can be reproduced with three distinct theoretical scenarios: a) a pileup in the EED due to stochastic acceleration; b) a structured jet with two-SSC emitting regions, with one region dominated by an extremely narrow EED; and c) an emission from an IC pair cascade.
The large jet kinetic power and non-thermal processes occurring in the microquasar SS 433 make this source a good candidate for a very high-energy (VHE) gamma-ray emitter. Gamma-ray fluxes have been ...predicted for both the central binary and the interaction regions between jets and surrounding nebula. Also, non-thermal emission at lower energies has been previously reported. We explore the capability of SS 433 to emit VHE gamma rays during periods in which the expected flux attenuation due to periodic eclipses and precession of the circumstellar disk periodically covering the central binary system is expected to be at its minimum. The eastern and western SS433/W50 interaction regions are also examined. We aim to constrain some theoretical models previously developed for this system. We made use of dedicated observations from MAGIC and H.E.S.S. from 2006 to 2011 which were combined for the first time and accounted for a total effective observation time of 16.5 h. Gamma-ray attenuation does not affect the jet/medium interaction regions. The analysis of a larger data set amounting to 40-80 h, depending on the region, was employed. No evidence of VHE gamma-ray emission was found. Upper limits were computed for the combined data set. We place constraints on the particle acceleration fraction at the inner jet regions and on the physics of the jet/medium interactions. Our findings suggest that the fraction of the jet kinetic power transferred to relativistic protons must be relatively small to explain the lack of TeV and neutrino emission from the central system. At the SS433/W50 interface, the presence of magnetic fields greater 10\(\mu\)G is derived assuming a synchrotron origin for the observed X-ray emission. This also implies the presence of high-energy electrons with energies up to 50 TeV, preventing an efficient production of gamma-ray fluxes in these interaction regions.
Hereditary cancer predisposition gene testing allows the identification of individuals at high risk of cancer that may benefit from increased surveillance, chemoprevention, and prophylactic surgery. ...In order to implement clinical genetic strategies adapted to each population’s needs and intrinsic genetic characteristic, this review aims to present the current status of knowledge about the spectrum of
BRCA
pathogenic variants in Latin American populations. We have conducted a comprehensive review of 33 studies published between 1994 and 2015 reporting the prevalence and/or spectrum of
BRCA1
(OMIM 113705) and
BRCA2
(OMIM 600185) variants. The combined sample size for these studies consisted of 4835 individuals from 13 countries in Latin America and the Caribbean, as well as in Hispanics in the United States. A total of 167 unique pathogenic variants have been reported in the existing literature. In unselected breast cancer cases, the prevalence ranged from 1.2 to 27.1 %. Some countries presented a few recurrent pathogenic variants, while others were characterized by diverse, non-recurrent variants. The proportion of
BRCA
pathogenic variants shared between Hispanics in the United States and Latin American populations was estimated at 10.4 %. Within Latin America and the Caribbean, 8.2 % of the
BRCA
variants reported were present in more than one country. Countries with high prevalence of
BRCA
pathogenic variants may benefit from more aggressive testing strategies, while testing of recurrent variant panels might present a cost-effective solution for improving genetic testing in some, but not all, countries.
Omega-3 polyunsaturated fatty acids (n-3 PUFAs) have been reported to improve insulin sensitivity and glucose homeostasis in animal models of insulin resistance, but the involved mechanisms still ...remain unresolved. In this study, we evaluated the effects of fish oil (FO), a source of n-3 PUFAs, on obesity, insulin resistance and muscle mitochondrial function in mice fed a high-fat diet (HFD). C57Bl/6 male mice, 8 weeks old, were divided into four groups: control diet (C), high-fat diet (H), C+FO (CFO) and H+FO (HFO). FO was administered by oral gavage (2 g/kg b.w.), three times a week, starting 4 weeks before diet administration until the end of the experimental protocol. HFD-induced obesity and insulin resistance associated with impaired skeletal muscle mitochondrial function, as indicated by decreased oxygen consumption, tricarboxylic acid cycle intermediate (TCAi) contents (citrate, α-ketoglutarate, malate and oxaloacetate), oxidative phosphorylation protein content and mitochondrial biogenesis. These effects were associated with elevated reactive oxygen species production, decreased PGC1-a transcription and reduced Akt phosphorylation. The changes induced by the HFD were partially attenuated by FO, which decreased obesity and insulin resistance and increased mitochondrial function. In the H group, FO supplementation also improved oxygen consumption; increased TCAi content, and Akt and AMPK phosphorylation; and up-regulated mRNA expression of Gpat1, Pepck, catalase and mitochondrial proteins (Pgc1α, Pparα, Cpt1 and Ucp3). These results suggest that dietary FO attenuates the deleterious effects of the HFD (obesity and insulin resistance) by improving skeletal muscle mitochondrial function.
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