8 research outputs found
Metallicity evolution of AGNs from UV emission-lines based on a new index
We analyzed the evolution of the metallicity of the gas with the redshift for
a sample of AGNs in a very wide redshift range (0<z<4) using ultraviolet
emission-lines from the narrow-line regions (NLRs) and photoionization models.
The new index C43=log(CIV+CIII])/HeII is suggested as a metallicity indicator
for AGNs. Based on this indicator, we confirmed the no metallicity evolution of
NLRs with the redshift pointed out by previous works. We found that metallicity
of AGNs shows similar evolution than the one predicted by cosmic semi-analytic
models of galaxy formation set within the Cold Dark Matter merging hierarchy
(for z < 3). Our results predict a mean metallicity for local objects in
agreement with the solar value (12+log(O/H)=8.69). This value is about the same
that the maximum oxygen abundance value derived for the central parts of local
spiral galaxies. Very low metallicity log(Z/Z_{\odot})~ -0.8 for some objects
in the range 1.5 < z <3 is derived.Comment: 25 pages, 10 figures, accepted MNRA
Optical and mid-infrared neon abundance determinations in star-forming regions
We employed observational spectroscopic data of star-forming regions compiled
from the literature and photoionization models to analyse the neon ionic
abundances obtained using both optical and mid-infrared emission-lines.
Comparing Ne++/H+ ionic abundances from distinct methods, we found that, in
average, the abundances obtained via IR emission-lines are higher than those
obtained via optical lines by a factor of 4. Photoionization models with
abundance variations along the radius of the hypothetical nebula provide a
possible explanation for a large part of the difference between ionic
abundances via optical and infrared emission-lines. Ionization Correction
Factor (ICF) for the neon is obtained from direct determinations of ionic
fractions using infrared emission-lines. A constant Ne/O ratio (logNe/O \approx
-0.70) for a large range of metallicity, independently of the ICF used to
compute the neon total abundance is derived.Comment: 17 pages, 14 figures, accepted by MNRA
X-rays as dominant excitation mechanism of [Fe ii] and H2 emission lines in active galaxies
We investigate the excitation mechanisms of near-infrared [Fe ii] and H2
emission lines observed in Active Galactic Nuclei (AGNs). We built a
photoionization model grid considering a two-component continuum, one accounts
for the Big Bump component peaking at 1Ryd and another represents the X-ray
source that dominates the continuum emission at high energies. Photoionization
models considering as ionizing source a spectral energy distribution obtained
from photometric data of the Sy 2 Mrk 1066 taken from the literature were
considered. Results of these models were compared with a large sample of
observational long-slit and Integral field Unit (IFU) spectroscopy data of the
nuclear region for a sample of active objects. We found that the correlation
between the observational [Fe ii]{\lambda}1.2570 {\mu}m/Pa{\beta} vs.
H2{\lambda}2.1218 {\mu}m/Br{\gamma} is well reproduced by our models as well as
the relationships that involve the H2 emission line ratios observed in the
spectroscopic data.We conclude that the heating by X-rays produced by active
nuclei can be considered a common and very important mechanism of excitation of
[Fe ii] and H2.Comment: 10 pages, 9 figures, accepted by MNRA
Chemical abundance of the LINER galaxy UGC 4805 with SDSS-IV MaNGA
Chemical abundance determinations in Low-Ionization Nuclear Line Regions (LINERs) are especially complex and uncertain because the nature of the ionizing source of this kind of object is unknown. In this work, we study the oxygen abundance in relation to the hydrogen abundance (O/H) of the gas phase of the UGC 4805 LINER nucleus. Optical spectroscopic data from the Mapping Nearby Galaxies (MaNGA) survey was employed to derive the O/H abundance of the UGC 4805 nucleus based on the extrapolation of the disk abundance gradient, on calibrations between O/H abundance and strong emission-lines for Active Galactic Nuclei (AGNs) as well as on photoionization models built with the Cloudy code, assuming gas accretion into a black hole (AGN) and post-Asymptotic Giant Branch (p-AGB) stars with different effective temperatures. We found that abundance gradient extrapolations, AGN calibrations, AGN and p-AGB photoionization models produce similar O/H values for the UGC 4805 nucleus and similar ionization parameter values. The study demonstrated that the methods used to estimate the O/H abundance using nuclear emission-line ratios produce reliable results, which are in agreement with the O/H values obtained from the independent method of galactic metallicity gradient extrapolation. Finally, the results from the WHAN diagram combined with the fact that the high excitation level of the gas has to be maintained at kpc scales, we suggest that the main ionizing source of the UGC 4805 nucleus probably has a stellar origin rather than an AGN.Fil: Krabbe, Angela. Universidade Do Vale Do ParaĂba; BrasilFil: Oliveira, C. B.. Universidade Do Vale Do ParaĂba; BrasilFil: Zinchenko, I. A.. Universitat Ulm. Faculty Of Natural Sciences. Institute Of Theoretical Physics; AlemaniaFil: Hernández JimĂ©nez, J. A.. Universidad AndrĂ©s Bello; ChileFil: Dors, Oli L.. Universidade Do Vale Do ParaĂba; BrasilFil: Hägele, Guillermo Federico. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - La Plata. Instituto de AstrofĂsica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias AstronĂłmicas y GeofĂsicas. Instituto de AstrofĂsica La Plata; ArgentinaFil: Cardaci, Monica Viviana. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - La Plata. Instituto de AstrofĂsica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias AstronĂłmicas y GeofĂsicas. Instituto de AstrofĂsica La Plata; ArgentinaFil: Telles, N. R.. Universidade Do Vale Do ParaĂba; Brasi
Chemical abundance of the LINER galaxy UGC 4805 with SDSS-IV MaNGA
Chemical abundance determinations in Low-Ionization Nuclear Line Regions (LINERs) are especially complex and uncertain because the nature of the ionizing source of this kind of object is unknown. In this work, we study the oxygen abundance in relation to the hydrogen abundance (O/H) of the gas phase of the UGC 4805 LINER nucleus. Optical spectroscopic data from the Mapping Nearby Galaxies (MaNGA) survey was employed to derive the O/H abundance of the UGC 4805 nucleus based on the extrapolation of the disk abundance gradient, on calibrations between O/H abundance and strong emission-lines for Active Galactic Nuclei (AGNs) as well as on photoionization models built with the Cloudy code, assuming gas accretion into a black hole (AGN) and post-Asymptotic Giant Branch (p-AGB) stars with different effective temperatures. We found that abundance gradient extrapolations, AGN calibrations, AGN and p-AGB photoionization models produce similar O/H values for the UGC 4805 nucleus and similar ionization parameter values. The study demonstrated that the methods used to estimate the O/H abundance using nuclear emission-line ratios produce reliable results, which are in agreement with the O/H values obtained from the independent method of galactic metallicity gradient extrapolation. Finally, the results from the WHAN diagram combined with the fact that the high excitation level of the gas has to be maintained at kpc scales, we suggest that the main ionizing source of the UGC 4805 nucleus probably has a stellar origin rather than an AGN.Instituto de AstrofĂsica de La Plat
Multiple populations in globular clusters. Lessons learned from the Milky Way globular clusters
Recent progress in studies of globular clusters has shown that they are not
simple stellar populations, being rather made of multiple generations. Evidence
stems both from photometry and spectroscopy. A new paradigm is then arising for
the formation of massive star clusters, which includes several episodes of star
formation. While this provides an explanation for several features of globular
clusters, including the second parameter problem, it also opens new
perspectives about the relation between globular clusters and the halo of our
Galaxy, and by extension of all populations with a high specific frequency of
globular clusters, such as, e.g., giant elliptical galaxies. We review progress
in this area, focusing on the most recent studies. Several points remain to be
properly understood, in particular those concerning the nature of the polluters
producing the abundance pattern in the clusters and the typical timescale, the
range of cluster masses where this phenomenon is active, and the relation
between globular clusters and other satellites of our Galaxy.Comment: In press (The Astronomy and Astrophysics Review
Genotype-phenotype studies in nail-patella syndrome show that LMX1B mutation location is involved in the risk of developing nephropathy.
Contains fulltext :
47792.pdf (publisher's version ) (Closed access)Nail-patella syndrome (NPS) is characterized by developmental defects of dorsal limb structures, nephropathy, and glaucoma and is caused by heterozygous mutations in the LIM homeodomain transcription factor LMX1B. In order to identify possible genotype-phenotype correlations, we performed LMX1B mutation analysis and comprehensive investigations of limb, renal, ocular, and audiological characteristics in 106 subjects from 32 NPS families. Remarkable phenotypic variability at the individual, intrafamilial, and interfamilial level was observed for different NPS manifestations. Quantitative urinanalysis revealed proteinuria in 21.3% of individuals. Microalbuminuria was detected in 21.7% of subjects without overt proteinuria. Interestingly, nephropathy appeared significantly more frequent in females. A significant association was established between the presence of clinically relevant renal involvement in an NPS patient and a positive family history of nephropathy. We identified normal-tension glaucoma (NTG) and sensorineural hearing impairment as new symptoms associated with NPS. Sequencing of LMX1B revealed 18 different mutations, including six novel variants, in 28 families. Individuals with an LMX1B mutation located in the homeodomain showed significantly more frequent and higher values of proteinuria compared to subjects carrying mutations in the LIM domains. No clear genotype-phenotype association was apparent for extrarenal manifestations. This is the first study indicating that family history of nephropathy and mutation location might be important in precipitating individual risks for developing NPS renal disease. We suggest that the NPS phenotype is broader than previously described and that NTG and hearing impairment are part of NPS. Further studies on modifier factors are needed to understand the mechanisms underlying phenotypic heterogeneity