We report the results of the first spectroscopic study of the galaxy HRG 705, which belongs to th... more We report the results of the first spectroscopic study of the galaxy HRG 705, which belongs to the Solitaire class of peculiar (collisional) Ring Galaxies, which, in turn, are little studied. The nuclear emission-line spectrum resembles that of a star forming galaxy (H ii galaxy), with $\boldsymbol z = 0.0305$ and heliocentric velocity of v = 9 144 ± 36 km s−1. The nuclear region is dominated by intermediate and old stellar populations in addition to a contribution of 8 per cent of young stars. Based on the complex velocity profile along the slit position angle of 59○, we suggest that the nuclear region is composed by 2 bodies in gravitational interaction (a possible on-going merging). Analysis of the surface brightness distribution confirmed the existence of the second body, a probable intruder, which lies inside a central pseudo-bulge/disc. HRG 705 does not appear to be oxygen-rich, but it is slightly more (O/H)-enriched than the galaxies of our nearby Universe.
Chemical abundance determinations in Low-Ionization Nuclear Emission-line Regions (LINERs) are es... more Chemical abundance determinations in Low-Ionization Nuclear Emission-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 survey was employed to derive the O/H abundance of the UGC 4805 nucleus based on the extrapolation of the disc 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 ...
Monthly Notices of the Royal Astronomical Society: Letters
We use Gemini GMOS-IFU observations of three luminous nearby Seyfert galaxies (Mrk 79, Mrk 348, a... more We use Gemini GMOS-IFU observations of three luminous nearby Seyfert galaxies (Mrk 79, Mrk 348, and Mrk 607) to estimate the electron temperature (Te) fluctuations in the inner 0.4–1.1 kpc region of these galaxies. Based on Te determinations through the [O iii]λ5007/λ4363 emission line ratio of each spaxel, temperature variations are quantified by computing the integrated value of the temperature fluctuation parameter (t2) projected in the plane of the sky $t_{\rm A}^{\rm 2}$, for the first time in active galactic nuclei (AGNs). We find $t_{\rm A}^{\rm 2}$ values of 0.135, 0.039, and 0.015 for Mrk 79, Mrk 348, and Mrk 607, respectively, which are of the same order or larger than the maximum values reported in star-forming regions and planetary nebulae. Taking into account that $t_{\rm A}^{\rm 2}$ should be considered a lower limit of the total t2 in the nebular volume, the results suggest that the impact of such fluctuations on chemical abundance determinations can be important in s...
Monthly Notices of the Royal Astronomical Society: Letters
We present maps for the electron temperature in the inner kpc of three luminous Seyfert galaxies:... more We present maps for the electron temperature in the inner kpc of three luminous Seyfert galaxies: Mrk 79, Mrk 348, and Mrk 607 obtained from Gemini Multi-Object Spectrograph-integral field unit observations at spatial resolutions of ∼110–280 pc. We study the distributions of electron temperature in active galaxies and find temperatures varying in the range from ∼8000 to $\gtrsim 30\, 000\,$K. Shocks due to gas outflows play an important role in the observed temperature distributions of Mrk 79 and Mrk 348, while standard photoionization models reproduce the derived temperature values for Mrk 607. In Mrk 79 and Mrk 348, we find direct evidence for shock ionization with overall orientation orthogonal to the ionization axis, where shocks can be easily observed as the active galactic nuclei radiation field is shielded by the nuclear dusty torus. This also indicates that even when the ionization cones are narrow, the shocks can be much wider angle.
We build detailed composite models of photoionization and shock ionization based on the suma code... more We build detailed composite models of photoionization and shock ionization based on the suma code to reproduce emission lines emitted from the Narrow Line Regions (NLR) of Seyfert 2 nuclei. The aim of this work is to investigate diagram active galactic nucleus (AGN) positions according to shock parameters, shock effects on the gas temperature and ionization structures and derive a semi-empirical abundance calibration based on emission-line ratios little sensitive to the shock presence. The models were used to reproduce optical (3000 < λ(Å) < 7000) emission line intensities of 244 local ($z \: \lesssim \: 0.4$) Seyfert 2s, whose observational data were selected from Sloan Digital Sky Survey DR7. Our models suggest that shocks in Seyfert 2 nuclei have velocities in the range of 50–300 $\rm km \: s^{-1}$ and imply a narrower metallicity range ($0.6 \: \lesssim \: (Z/Z_{\odot }) \: \lesssim \: 1.6$) than those derived using pure photoionization models. Our results indicate that sh...
We investigate the discrepancy between oxygen abundance estimations for narrow-line regions of ac... more We investigate the discrepancy between oxygen abundance estimations for narrow-line regions of active galactic nuclei (AGNs) type Seyfert 2 derived using direct estimations of the electron temperature (Te-method) and those derived using photoionization models. In view of this, observational emission-line ratios in the optical range ($3000 \: \lt \: \lambda (\mathring{\rm A}) \: \lt 7000$) of Seyfert 2 nuclei compiled from the literature were reproduced by detailed photoionization models built with the cloudy code. We find that the derived discrepancies are mainly due to the inappropriate use of the relations between temperatures of the low (t2) and high (t3) ionization gas zones derived for H ii regions in AGN chemical abundance studies. Using a photoionization model grid, we derived a new expression for t2 as a function of t3 valid for Seyfert 2 nuclei. The use of this new expression in the AGN estimation of the O/H abundances based on Te-method produces O/H abundances slightly low...
We present a semi-empirical calibration between the metallicity (Z) of Seyfert 2 active galactic ... more We present a semi-empirical calibration between the metallicity (Z) of Seyfert 2 active galactic nuclei and the N2 = log([N ii]λ6584/H α) emission-line intensity ratio. This calibration was derived through the [O iii]λ5007/[O ii]λ3727 versus N2 diagram containing observational data and photoionization model results obtained with the cloudy code. The observational sample consists of 463 confirmed Seyfert 2 nuclei (redshift $z \: \lesssim 0.4$) taken from the Sloan Digital Sky Survey DR7 data set. The obtained Z–N2 relation is valid for the range $0.3 \: \lesssim \: (Z/{\rm Z}_{\odot }) \: \lesssim \: 2.0$ that corresponds to $-0.7 \: \lesssim \: ({\rm N}2) \: \lesssim \: 0.6$. The effects of varying the ionization parameter (U), electron density and the slope of the spectral energy distribution on the Z estimations are of the order of the uncertainty produced by the error measurements of N2. This result indicates the large reliability of our Z –N2 calibration. A relation between U an...
We compare the oxygen abundance (O/H) of the Narrow Line Regions (NLRs) of Seyfert 2 AGNs obtaine... more We compare the oxygen abundance (O/H) of the Narrow Line Regions (NLRs) of Seyfert 2 AGNs obtained through strong-line methods and from direct measurements of the electron temperature (Te-method). The aim of this study is to explore the effects of the use of distinct methods on the range of metallicity and on the mass-metallicity relation of AGNs at low redshifts ($z \: \lesssim \: 0.4$). We used the Sloan Digital Sky Survey (SDSS) and NASA/IPAC Extragalactic Database (NED) to selected optical (3000 < λ(Å) < 7000) emission line intensities of 463 confirmed Seyfert 2 AGNs. The oxygen abundance of the NLRs were estimated using the theoretical Storchi-Bergmann et al. calibrations, the semi-empirical N2O2 calibration, the bayesian H ii-Chi-mistry code and the Te-method. We found that the oxygen abundance estimations via the strong-line methods differ from each other up to ∼0.8 dex, with the largest discrepancies in the low metallicity regime ($\rm 12+\log (O/H) \: \lesssim \: 8.5$...
Integral Field Spectroscopy (IFS) is well known for providing detailed insight of extended source... more Integral Field Spectroscopy (IFS) is well known for providing detailed insight of extended sources thanks to the possibility of handling space resolved spectroscopic information. Simple and straightforward analysis such as single line fitting yield interesting results, although it might miss a more complete picture in many cases. Violent star forming regions, such as starburst galaxies, display very complex emission line profiles due to multiple kinematic components superposed in the line of sight. We perform a spatially resolved kinematical study of a single Green Pea (GP) galaxy, SDSSJ083843.63+385350.5, using a new method for analyzing Integral Field Unit (IFU) observations of emission line spectra. The method considers the presence of multiple components in the emission-line profiles and makes use of a statistical indicator to determine the meaningful number of components to fit the observed profiles. We are able to identify three distinct kinematic features throughout the field...
The Southern Photometric Local Universe Survey (S-PLUS) is imaging ∼9300deg2 of the celestial sph... more The Southern Photometric Local Universe Survey (S-PLUS) is imaging ∼9300deg2 of the celestial sphere in twelve optical bands using a dedicated 0.8 m robotic telescope, the T80-South, at the Cerro Tololo Inter-american Observatory, Chile. The telescope is equipped with a 9.2k×9.2k e2v detector with 10 μm pixels, resulting in a field-of-view of 2 deg2 with a plate scale of 0.55” pixel−1. The survey consists of four main subfields, which include two non-contiguous fields at high Galactic latitudes (|b| > 30○, 8000deg2) and two areas of the Galactic plane and bulge (for an additional 1300deg2). S-PLUS uses the Javalambre 12-band magnitude system, which includes the 5 ugriz broad-band filters and 7 narrow-band filters centered on prominent stellar spectral features: the Balmer jump/[OII], Ca H+K, Hδ, G-band, Mg b triplet, Hα, and the Ca triplet. S-PLUS delivers accurate photometric redshifts (δz/(1 + z) = 0.02 or better) for galaxies with r < 20 AB mag and z < 0.5, thus producin...
We present a detailed spatial analysis of stellar populations based on long-slit optical spectra ... more We present a detailed spatial analysis of stellar populations based on long-slit optical spectra in a sample of eight luminous early-type galaxies selected from nearby sparse groups and pairs, three of them may have interaction with another galaxy of similar mass. We have spatially measured luminosityweighted averages of age, [M/H], [Fe/H], and [α/Fe] in the sample galaxies to add empirical data relative to the influence of galaxy mass, environment, interaction, and AGN feedback in their formation and evolution. The stellar population of the individual galaxies were determined through the well-established stellar population synthesis code STARLIGHT using semi-empirical simple stellar population models. Radial variations of luminosity-weighted means of age, [M/H], [Fe/H], and [α/Fe] were quantified up to half of the effective radius of each galaxy. We found trends between representative values of age, [M/H], [α/Fe], and the nuclear stellar velocity dispersion. There are also relations between the metallicity/age gradients and the velocity dispersion. Contributions of 1 − 4 Gyr old stellar populations were quantified in IC 5328 and NGC 6758 as well as 4−8 Gyr old ones in NGC 5812. Extended gas is present in IC 5328, NGC 1052, NGC 1209, and NGC 6758, and the presence of a LINER is identified in all these galaxies. The regions up to one effective radius of all galaxies are basically dominated by α-enhanced metal-rich old stellar populations likely due to rapid star formation episodes that induced efficient chemical enrichment. On average, the age and [α/Fe] gradients are null and the [M/H] gradients are negative, although discordant cases were found. We found no correlation between the stellar population properties and the LINER presence as well as between the stellar properties and environment or gravitational interaction, suggesting that the influence of progenitor mass cannot be discarded in the formation and evolution of early-type galaxies.
We derived two semi-empirical calibrations between the metallicity of the narrow-line region (NLR... more We derived two semi-empirical calibrations between the metallicity of the narrow-line region (NLR) of type-2 active galactic nuclei and the rest frame of the N V λ1240/He II λ1640, C43 = log[(C IV λ1549 + C III]λ1909)/He II λ1640], and C III]λ1909/C IV λ1549 emissionline intensity ratios. A metallicity-independent calibration between the ionization parameter and the C III]λ1909/C IV λ1549 emission-lines ratio was also derived. These calibrations were obtained comparing ratios of measured UV emission-line intensities, compiled from the literature, for a sample of 77 objects (redshift 0 < z < 3.8) with those predicted by a grid of photoionization models built with the CLOUDY code. Using the derived calibrations, it was possible to show that the metallicity estimations for NLRs are lower by a factor of about 2-3 than those for broad-line regions. Besides, we confirmed the recent result of the existence of a relation between the stellar mass of the host galaxy and its NLR metallicity. We also derived an M-Z relation for the objects in our sample at 1.6 < z < 3.8. This relation seems to follow the same trend as the ones estimated for star-forming galaxies of similar high redshifts but for higher masses.
In this work, we used a grid of photoionization models combined with stellar population synthesis... more In this work, we used a grid of photoionization models combined with stellar population synthesis models to derive reliable ionization correction factors (ICFs) for the sulphur in starforming regions. These models cover a large range of nebular parameters and yielding ionic abundances in consonance with those derived through optical and infrared observational data of star-forming regions. From our theoretical ICFs, we suggested an α value of 3.27 ± 0.01 in the classical Stasińska formulae. We compared the total sulphur abundance in the gas phase of a large sample of objects by using our theoretical ICF and other approaches. In average, the differences between the determinations via the use of the different ICFs considered are similar to the uncertainties in the S/H estimations. Nevertheless, we noted that for some objects it could reach up to about 0.3 dex for the low-metallicity regime. Despite of the large scatter of the points, we found a trend of S/O ratio to decrease with the metallicity, independently of the ICF used to compute the sulphur total abundance.
We built a grid of photoionization models and compiled already available observational emission l... more We built a grid of photoionization models and compiled already available observational emission line intensities (1000 < λ(Å) < 2000) of confirmed star formation regions and Active Galactic Nucleus (AGNs) in order to classify five Lyα emitter (LAE) objects at high redshift (5.7 < z < 7.2). We selected objects for which at least one metal emissionline was measured. The resulting sample is composed by the objects RXC J2248.7-4431-ID3, HSC J233408+004403, COSY, A1703-zd6, and CR7 (clump C). The photoionization models were built assuming a Power Law (associated with the presence of an AGN), a Direct Collapse Black Hole (DCBH), and Population II stars for the ionizing source. The resulting models were then compared with observational emission-line ratios in six diagnostic diagrams to produce a spectral classification of the sample. We found that CR7 (clump C), HSC J233408+004403 and COSY probably have a non thermal ionizing source (AGN or DCBH) while the RXC J2248.7-4431-ID3 and A1703-zd6 seem to host a stellar cluster. Detailed photoionization models were constructed to reproduce observational emission line ratios of the sample of LAEs, and to derive chemical abundances and number of ionizing photons Q(H) of these objects. From these models, we found metallicities in the range 0.1 (Z/Z) 0.5 and log Q(H) > 53. Values for C/O abundance ratio derived for the LAEs seem to be consistent with those derived for local star forming objects with similar metallicities, while an overabundance of N/O was found for most of the LAEs.
We present an observational study of the galaxy HRG 54103, a peculiar galaxy with an asymmetric d... more We present an observational study of the galaxy HRG 54103, a peculiar galaxy with an asymmetric disc ring. The main goal of this work is to study the stellar population and oxygen abundances for the inner bulge region. The kinematics derived from long-slit spectroscopy suggest that the line of nodes of the gaseous component of HRG 54103 is nearly along the galaxy ring minor axis. The gaseous disc seems to be kinematically decoupled relative to the morphology of the stellar ring. A small, but non-negligible, fraction of young stars (5-10 per cent) is estimated to contribute. This object is mainly dominated by old and intermediate stellar populations. The emission-line spectrum shows low-ionization nuclear emission-line region (LINER) type characteristics. We determined oxygen abundances using calibrations between this parameter and the strong emission line ratios known as the indices O3N2 and N2. Our results suggest a relatively homogeneous O/H across the minor axis of the galaxy, with average values of 12 + log(O/H) = 8.4 dex and 12 + log(O/H) = 8.7 dex, using the O3N2 and N2 parameters, respectively. These values are compatible with the few estimations of oxygen abundance for peculiar ring galaxies published in the literature. Implications on the formation history of HRG 54103 were investigated.
We analysed the evolution of the metallicity of the gas with the redshift for a sample of AGNs in... more We analysed 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[(C IV+C III])/He II] 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 semianalytic 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) ≈ −0.8 for some objects in the range 1.5 < z < 3 is derived.
The effective temperature (T eff) of the radiation field of the ionizing star(s) of a large sampl... more The effective temperature (T eff) of the radiation field of the ionizing star(s) of a large sample of extragalactic H ii regions was estimated using the R=log([O ii](λλ3726+29)/[O iii]λ5007) index. We used a grid of photoionization models to calibrate the T eff-R relation finding that it has a strong dependence with the ionizing parameter while it shows a weak direct dependence with the metallicity (variations in Z imply variations in U) of both the stellar atmosphere of the ionizing star and the gas phase of the H ii region. Since the R index varies slightly with the T eff for values larger than 40 kK, the R index can be used to derive the T eff in the 30 − 40 kK range. A large fraction of the ionization parameter variation is due to differences in the temperature of the ionizing stars and then the use of the (relatively) low T eff dependent S2=[S ii](λλ6717+31)/Hα emission-line ratio to derive the ionization parameter is preferable over others in the literature. We propose linear metallicity dependent relationships between S2 and U. T eff and metallicity estimations for a sample of 865 H ii regions, whose emission-line intensities were compiled from the literature, do not show any T eff-Z correlation. On the other hand it seems to be hints of the presence of an anti-correlation between T eff-U. We found that the majority of the studied H ii regions (∼ 87%) present T eff values in the range between 37 and 40 kK, with an average value of 38.5(±1) kK. We also studied the variation of T eff as a function of the galactocentric distance for 14 spiral galaxies. Our results are in agreement with the idea of the existence of positive T eff gradients along the disk of spiral galaxies.
Monthly Notices of the Royal Astronomical Society, 2015
We investigate interaction effects on the dynamics and morphology of the galaxy pairs AM 2058-381... more We investigate interaction effects on the dynamics and morphology of the galaxy pairs AM 2058-381 and AM 1228-260. This work is based on r images and longslit spectra obtained with the Gemini Multi-Object Spectrograph at the Gemini South Telescope. The luminosity ratio between the main (AM 2058A) and secondary (AM 2058B) components of the first pair is a factor of ∼ 5, while for the other pair, the main (AM 1228A) component is 20 times more luminous than the secondary (AM 1228B). The four galaxies have pseudo-bulges, with a Sérsic index n < 2. Their observed radial velocities profiles (RVPs) present several irregularities. The receding side of the RVP of AM 2058A is displaced with respect to the velocity field model, while there is a strong evidence that AM 2058B is a tumbling body, rotating along its major axis. The RVPs for AM 1228A indicate a misalignment between the kinematic and photometric major axes. The RVP for AM 1228B is quite perturbed, very likely due to the interaction with AM 1228A. NFW halo parameters for AM 2058A are similar to those of the Milky Way and M 31. The halo mass of AM 1228A is roughly 10% that of AM 2058A. The mass-to-light (M/L) of AM 2058 agrees with the mean value derived for late-type spirals, while the low M/L for AM 1228A may be due to the intense star formation ongoing in this galaxy.
Monthly Notices of the Royal Astronomical Society, 2015
We examine the relation between oxygen abundances in the narrow-line regions (NLRs) of active gal... more We examine the relation between oxygen abundances in the narrow-line regions (NLRs) of active galactic nuclei (AGNs) estimated from the optical emission lines through the strong-line method (the theoretical calibration of Storchi-Bergmann et al. 1998), via the direct T e-method, and the central intersect abundances in the host galaxies determined from the radial abundance gradients. We found that the T e-method underestimates the oxygen abundances by up to ∼2 dex (with average value of ∼ 0.8 dex) compared to the abundances derived through the strong-line method. This confirms the existence of the so-called "temperature problem" in AGNs. We also found that the abundances in the centres of galaxies obtained from their spectra trough the strong-line method are close to or slightly lower than the central intersect abundances estimated from the radial abundance gradient both in AGNs and Star-forming galaxies. The oxygen abundance of the NLR is usually lower than the maximum attainable abundance in galaxies (∼2 times the solar value). This suggests that there is no extraordinary chemical enrichment of the NLRs of AGNs.
We report the results of the first spectroscopic study of the galaxy HRG 705, which belongs to th... more We report the results of the first spectroscopic study of the galaxy HRG 705, which belongs to the Solitaire class of peculiar (collisional) Ring Galaxies, which, in turn, are little studied. The nuclear emission-line spectrum resembles that of a star forming galaxy (H ii galaxy), with $\boldsymbol z = 0.0305$ and heliocentric velocity of v = 9 144 ± 36 km s−1. The nuclear region is dominated by intermediate and old stellar populations in addition to a contribution of 8 per cent of young stars. Based on the complex velocity profile along the slit position angle of 59○, we suggest that the nuclear region is composed by 2 bodies in gravitational interaction (a possible on-going merging). Analysis of the surface brightness distribution confirmed the existence of the second body, a probable intruder, which lies inside a central pseudo-bulge/disc. HRG 705 does not appear to be oxygen-rich, but it is slightly more (O/H)-enriched than the galaxies of our nearby Universe.
Chemical abundance determinations in Low-Ionization Nuclear Emission-line Regions (LINERs) are es... more Chemical abundance determinations in Low-Ionization Nuclear Emission-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 survey was employed to derive the O/H abundance of the UGC 4805 nucleus based on the extrapolation of the disc 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 ...
Monthly Notices of the Royal Astronomical Society: Letters
We use Gemini GMOS-IFU observations of three luminous nearby Seyfert galaxies (Mrk 79, Mrk 348, a... more We use Gemini GMOS-IFU observations of three luminous nearby Seyfert galaxies (Mrk 79, Mrk 348, and Mrk 607) to estimate the electron temperature (Te) fluctuations in the inner 0.4–1.1 kpc region of these galaxies. Based on Te determinations through the [O iii]λ5007/λ4363 emission line ratio of each spaxel, temperature variations are quantified by computing the integrated value of the temperature fluctuation parameter (t2) projected in the plane of the sky $t_{\rm A}^{\rm 2}$, for the first time in active galactic nuclei (AGNs). We find $t_{\rm A}^{\rm 2}$ values of 0.135, 0.039, and 0.015 for Mrk 79, Mrk 348, and Mrk 607, respectively, which are of the same order or larger than the maximum values reported in star-forming regions and planetary nebulae. Taking into account that $t_{\rm A}^{\rm 2}$ should be considered a lower limit of the total t2 in the nebular volume, the results suggest that the impact of such fluctuations on chemical abundance determinations can be important in s...
Monthly Notices of the Royal Astronomical Society: Letters
We present maps for the electron temperature in the inner kpc of three luminous Seyfert galaxies:... more We present maps for the electron temperature in the inner kpc of three luminous Seyfert galaxies: Mrk 79, Mrk 348, and Mrk 607 obtained from Gemini Multi-Object Spectrograph-integral field unit observations at spatial resolutions of ∼110–280 pc. We study the distributions of electron temperature in active galaxies and find temperatures varying in the range from ∼8000 to $\gtrsim 30\, 000\,$K. Shocks due to gas outflows play an important role in the observed temperature distributions of Mrk 79 and Mrk 348, while standard photoionization models reproduce the derived temperature values for Mrk 607. In Mrk 79 and Mrk 348, we find direct evidence for shock ionization with overall orientation orthogonal to the ionization axis, where shocks can be easily observed as the active galactic nuclei radiation field is shielded by the nuclear dusty torus. This also indicates that even when the ionization cones are narrow, the shocks can be much wider angle.
We build detailed composite models of photoionization and shock ionization based on the suma code... more We build detailed composite models of photoionization and shock ionization based on the suma code to reproduce emission lines emitted from the Narrow Line Regions (NLR) of Seyfert 2 nuclei. The aim of this work is to investigate diagram active galactic nucleus (AGN) positions according to shock parameters, shock effects on the gas temperature and ionization structures and derive a semi-empirical abundance calibration based on emission-line ratios little sensitive to the shock presence. The models were used to reproduce optical (3000 < λ(Å) < 7000) emission line intensities of 244 local ($z \: \lesssim \: 0.4$) Seyfert 2s, whose observational data were selected from Sloan Digital Sky Survey DR7. Our models suggest that shocks in Seyfert 2 nuclei have velocities in the range of 50–300 $\rm km \: s^{-1}$ and imply a narrower metallicity range ($0.6 \: \lesssim \: (Z/Z_{\odot }) \: \lesssim \: 1.6$) than those derived using pure photoionization models. Our results indicate that sh...
We investigate the discrepancy between oxygen abundance estimations for narrow-line regions of ac... more We investigate the discrepancy between oxygen abundance estimations for narrow-line regions of active galactic nuclei (AGNs) type Seyfert 2 derived using direct estimations of the electron temperature (Te-method) and those derived using photoionization models. In view of this, observational emission-line ratios in the optical range ($3000 \: \lt \: \lambda (\mathring{\rm A}) \: \lt 7000$) of Seyfert 2 nuclei compiled from the literature were reproduced by detailed photoionization models built with the cloudy code. We find that the derived discrepancies are mainly due to the inappropriate use of the relations between temperatures of the low (t2) and high (t3) ionization gas zones derived for H ii regions in AGN chemical abundance studies. Using a photoionization model grid, we derived a new expression for t2 as a function of t3 valid for Seyfert 2 nuclei. The use of this new expression in the AGN estimation of the O/H abundances based on Te-method produces O/H abundances slightly low...
We present a semi-empirical calibration between the metallicity (Z) of Seyfert 2 active galactic ... more We present a semi-empirical calibration between the metallicity (Z) of Seyfert 2 active galactic nuclei and the N2 = log([N ii]λ6584/H α) emission-line intensity ratio. This calibration was derived through the [O iii]λ5007/[O ii]λ3727 versus N2 diagram containing observational data and photoionization model results obtained with the cloudy code. The observational sample consists of 463 confirmed Seyfert 2 nuclei (redshift $z \: \lesssim 0.4$) taken from the Sloan Digital Sky Survey DR7 data set. The obtained Z–N2 relation is valid for the range $0.3 \: \lesssim \: (Z/{\rm Z}_{\odot }) \: \lesssim \: 2.0$ that corresponds to $-0.7 \: \lesssim \: ({\rm N}2) \: \lesssim \: 0.6$. The effects of varying the ionization parameter (U), electron density and the slope of the spectral energy distribution on the Z estimations are of the order of the uncertainty produced by the error measurements of N2. This result indicates the large reliability of our Z –N2 calibration. A relation between U an...
We compare the oxygen abundance (O/H) of the Narrow Line Regions (NLRs) of Seyfert 2 AGNs obtaine... more We compare the oxygen abundance (O/H) of the Narrow Line Regions (NLRs) of Seyfert 2 AGNs obtained through strong-line methods and from direct measurements of the electron temperature (Te-method). The aim of this study is to explore the effects of the use of distinct methods on the range of metallicity and on the mass-metallicity relation of AGNs at low redshifts ($z \: \lesssim \: 0.4$). We used the Sloan Digital Sky Survey (SDSS) and NASA/IPAC Extragalactic Database (NED) to selected optical (3000 < λ(Å) < 7000) emission line intensities of 463 confirmed Seyfert 2 AGNs. The oxygen abundance of the NLRs were estimated using the theoretical Storchi-Bergmann et al. calibrations, the semi-empirical N2O2 calibration, the bayesian H ii-Chi-mistry code and the Te-method. We found that the oxygen abundance estimations via the strong-line methods differ from each other up to ∼0.8 dex, with the largest discrepancies in the low metallicity regime ($\rm 12+\log (O/H) \: \lesssim \: 8.5$...
Integral Field Spectroscopy (IFS) is well known for providing detailed insight of extended source... more Integral Field Spectroscopy (IFS) is well known for providing detailed insight of extended sources thanks to the possibility of handling space resolved spectroscopic information. Simple and straightforward analysis such as single line fitting yield interesting results, although it might miss a more complete picture in many cases. Violent star forming regions, such as starburst galaxies, display very complex emission line profiles due to multiple kinematic components superposed in the line of sight. We perform a spatially resolved kinematical study of a single Green Pea (GP) galaxy, SDSSJ083843.63+385350.5, using a new method for analyzing Integral Field Unit (IFU) observations of emission line spectra. The method considers the presence of multiple components in the emission-line profiles and makes use of a statistical indicator to determine the meaningful number of components to fit the observed profiles. We are able to identify three distinct kinematic features throughout the field...
The Southern Photometric Local Universe Survey (S-PLUS) is imaging ∼9300deg2 of the celestial sph... more The Southern Photometric Local Universe Survey (S-PLUS) is imaging ∼9300deg2 of the celestial sphere in twelve optical bands using a dedicated 0.8 m robotic telescope, the T80-South, at the Cerro Tololo Inter-american Observatory, Chile. The telescope is equipped with a 9.2k×9.2k e2v detector with 10 μm pixels, resulting in a field-of-view of 2 deg2 with a plate scale of 0.55” pixel−1. The survey consists of four main subfields, which include two non-contiguous fields at high Galactic latitudes (|b| > 30○, 8000deg2) and two areas of the Galactic plane and bulge (for an additional 1300deg2). S-PLUS uses the Javalambre 12-band magnitude system, which includes the 5 ugriz broad-band filters and 7 narrow-band filters centered on prominent stellar spectral features: the Balmer jump/[OII], Ca H+K, Hδ, G-band, Mg b triplet, Hα, and the Ca triplet. S-PLUS delivers accurate photometric redshifts (δz/(1 + z) = 0.02 or better) for galaxies with r < 20 AB mag and z < 0.5, thus producin...
We present a detailed spatial analysis of stellar populations based on long-slit optical spectra ... more We present a detailed spatial analysis of stellar populations based on long-slit optical spectra in a sample of eight luminous early-type galaxies selected from nearby sparse groups and pairs, three of them may have interaction with another galaxy of similar mass. We have spatially measured luminosityweighted averages of age, [M/H], [Fe/H], and [α/Fe] in the sample galaxies to add empirical data relative to the influence of galaxy mass, environment, interaction, and AGN feedback in their formation and evolution. The stellar population of the individual galaxies were determined through the well-established stellar population synthesis code STARLIGHT using semi-empirical simple stellar population models. Radial variations of luminosity-weighted means of age, [M/H], [Fe/H], and [α/Fe] were quantified up to half of the effective radius of each galaxy. We found trends between representative values of age, [M/H], [α/Fe], and the nuclear stellar velocity dispersion. There are also relations between the metallicity/age gradients and the velocity dispersion. Contributions of 1 − 4 Gyr old stellar populations were quantified in IC 5328 and NGC 6758 as well as 4−8 Gyr old ones in NGC 5812. Extended gas is present in IC 5328, NGC 1052, NGC 1209, and NGC 6758, and the presence of a LINER is identified in all these galaxies. The regions up to one effective radius of all galaxies are basically dominated by α-enhanced metal-rich old stellar populations likely due to rapid star formation episodes that induced efficient chemical enrichment. On average, the age and [α/Fe] gradients are null and the [M/H] gradients are negative, although discordant cases were found. We found no correlation between the stellar population properties and the LINER presence as well as between the stellar properties and environment or gravitational interaction, suggesting that the influence of progenitor mass cannot be discarded in the formation and evolution of early-type galaxies.
We derived two semi-empirical calibrations between the metallicity of the narrow-line region (NLR... more We derived two semi-empirical calibrations between the metallicity of the narrow-line region (NLR) of type-2 active galactic nuclei and the rest frame of the N V λ1240/He II λ1640, C43 = log[(C IV λ1549 + C III]λ1909)/He II λ1640], and C III]λ1909/C IV λ1549 emissionline intensity ratios. A metallicity-independent calibration between the ionization parameter and the C III]λ1909/C IV λ1549 emission-lines ratio was also derived. These calibrations were obtained comparing ratios of measured UV emission-line intensities, compiled from the literature, for a sample of 77 objects (redshift 0 < z < 3.8) with those predicted by a grid of photoionization models built with the CLOUDY code. Using the derived calibrations, it was possible to show that the metallicity estimations for NLRs are lower by a factor of about 2-3 than those for broad-line regions. Besides, we confirmed the recent result of the existence of a relation between the stellar mass of the host galaxy and its NLR metallicity. We also derived an M-Z relation for the objects in our sample at 1.6 < z < 3.8. This relation seems to follow the same trend as the ones estimated for star-forming galaxies of similar high redshifts but for higher masses.
In this work, we used a grid of photoionization models combined with stellar population synthesis... more In this work, we used a grid of photoionization models combined with stellar population synthesis models to derive reliable ionization correction factors (ICFs) for the sulphur in starforming regions. These models cover a large range of nebular parameters and yielding ionic abundances in consonance with those derived through optical and infrared observational data of star-forming regions. From our theoretical ICFs, we suggested an α value of 3.27 ± 0.01 in the classical Stasińska formulae. We compared the total sulphur abundance in the gas phase of a large sample of objects by using our theoretical ICF and other approaches. In average, the differences between the determinations via the use of the different ICFs considered are similar to the uncertainties in the S/H estimations. Nevertheless, we noted that for some objects it could reach up to about 0.3 dex for the low-metallicity regime. Despite of the large scatter of the points, we found a trend of S/O ratio to decrease with the metallicity, independently of the ICF used to compute the sulphur total abundance.
We built a grid of photoionization models and compiled already available observational emission l... more We built a grid of photoionization models and compiled already available observational emission line intensities (1000 < λ(Å) < 2000) of confirmed star formation regions and Active Galactic Nucleus (AGNs) in order to classify five Lyα emitter (LAE) objects at high redshift (5.7 < z < 7.2). We selected objects for which at least one metal emissionline was measured. The resulting sample is composed by the objects RXC J2248.7-4431-ID3, HSC J233408+004403, COSY, A1703-zd6, and CR7 (clump C). The photoionization models were built assuming a Power Law (associated with the presence of an AGN), a Direct Collapse Black Hole (DCBH), and Population II stars for the ionizing source. The resulting models were then compared with observational emission-line ratios in six diagnostic diagrams to produce a spectral classification of the sample. We found that CR7 (clump C), HSC J233408+004403 and COSY probably have a non thermal ionizing source (AGN or DCBH) while the RXC J2248.7-4431-ID3 and A1703-zd6 seem to host a stellar cluster. Detailed photoionization models were constructed to reproduce observational emission line ratios of the sample of LAEs, and to derive chemical abundances and number of ionizing photons Q(H) of these objects. From these models, we found metallicities in the range 0.1 (Z/Z) 0.5 and log Q(H) > 53. Values for C/O abundance ratio derived for the LAEs seem to be consistent with those derived for local star forming objects with similar metallicities, while an overabundance of N/O was found for most of the LAEs.
We present an observational study of the galaxy HRG 54103, a peculiar galaxy with an asymmetric d... more We present an observational study of the galaxy HRG 54103, a peculiar galaxy with an asymmetric disc ring. The main goal of this work is to study the stellar population and oxygen abundances for the inner bulge region. The kinematics derived from long-slit spectroscopy suggest that the line of nodes of the gaseous component of HRG 54103 is nearly along the galaxy ring minor axis. The gaseous disc seems to be kinematically decoupled relative to the morphology of the stellar ring. A small, but non-negligible, fraction of young stars (5-10 per cent) is estimated to contribute. This object is mainly dominated by old and intermediate stellar populations. The emission-line spectrum shows low-ionization nuclear emission-line region (LINER) type characteristics. We determined oxygen abundances using calibrations between this parameter and the strong emission line ratios known as the indices O3N2 and N2. Our results suggest a relatively homogeneous O/H across the minor axis of the galaxy, with average values of 12 + log(O/H) = 8.4 dex and 12 + log(O/H) = 8.7 dex, using the O3N2 and N2 parameters, respectively. These values are compatible with the few estimations of oxygen abundance for peculiar ring galaxies published in the literature. Implications on the formation history of HRG 54103 were investigated.
We analysed the evolution of the metallicity of the gas with the redshift for a sample of AGNs in... more We analysed 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[(C IV+C III])/He II] 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 semianalytic 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) ≈ −0.8 for some objects in the range 1.5 < z < 3 is derived.
The effective temperature (T eff) of the radiation field of the ionizing star(s) of a large sampl... more The effective temperature (T eff) of the radiation field of the ionizing star(s) of a large sample of extragalactic H ii regions was estimated using the R=log([O ii](λλ3726+29)/[O iii]λ5007) index. We used a grid of photoionization models to calibrate the T eff-R relation finding that it has a strong dependence with the ionizing parameter while it shows a weak direct dependence with the metallicity (variations in Z imply variations in U) of both the stellar atmosphere of the ionizing star and the gas phase of the H ii region. Since the R index varies slightly with the T eff for values larger than 40 kK, the R index can be used to derive the T eff in the 30 − 40 kK range. A large fraction of the ionization parameter variation is due to differences in the temperature of the ionizing stars and then the use of the (relatively) low T eff dependent S2=[S ii](λλ6717+31)/Hα emission-line ratio to derive the ionization parameter is preferable over others in the literature. We propose linear metallicity dependent relationships between S2 and U. T eff and metallicity estimations for a sample of 865 H ii regions, whose emission-line intensities were compiled from the literature, do not show any T eff-Z correlation. On the other hand it seems to be hints of the presence of an anti-correlation between T eff-U. We found that the majority of the studied H ii regions (∼ 87%) present T eff values in the range between 37 and 40 kK, with an average value of 38.5(±1) kK. We also studied the variation of T eff as a function of the galactocentric distance for 14 spiral galaxies. Our results are in agreement with the idea of the existence of positive T eff gradients along the disk of spiral galaxies.
Monthly Notices of the Royal Astronomical Society, 2015
We investigate interaction effects on the dynamics and morphology of the galaxy pairs AM 2058-381... more We investigate interaction effects on the dynamics and morphology of the galaxy pairs AM 2058-381 and AM 1228-260. This work is based on r images and longslit spectra obtained with the Gemini Multi-Object Spectrograph at the Gemini South Telescope. The luminosity ratio between the main (AM 2058A) and secondary (AM 2058B) components of the first pair is a factor of ∼ 5, while for the other pair, the main (AM 1228A) component is 20 times more luminous than the secondary (AM 1228B). The four galaxies have pseudo-bulges, with a Sérsic index n < 2. Their observed radial velocities profiles (RVPs) present several irregularities. The receding side of the RVP of AM 2058A is displaced with respect to the velocity field model, while there is a strong evidence that AM 2058B is a tumbling body, rotating along its major axis. The RVPs for AM 1228A indicate a misalignment between the kinematic and photometric major axes. The RVP for AM 1228B is quite perturbed, very likely due to the interaction with AM 1228A. NFW halo parameters for AM 2058A are similar to those of the Milky Way and M 31. The halo mass of AM 1228A is roughly 10% that of AM 2058A. The mass-to-light (M/L) of AM 2058 agrees with the mean value derived for late-type spirals, while the low M/L for AM 1228A may be due to the intense star formation ongoing in this galaxy.
Monthly Notices of the Royal Astronomical Society, 2015
We examine the relation between oxygen abundances in the narrow-line regions (NLRs) of active gal... more We examine the relation between oxygen abundances in the narrow-line regions (NLRs) of active galactic nuclei (AGNs) estimated from the optical emission lines through the strong-line method (the theoretical calibration of Storchi-Bergmann et al. 1998), via the direct T e-method, and the central intersect abundances in the host galaxies determined from the radial abundance gradients. We found that the T e-method underestimates the oxygen abundances by up to ∼2 dex (with average value of ∼ 0.8 dex) compared to the abundances derived through the strong-line method. This confirms the existence of the so-called "temperature problem" in AGNs. We also found that the abundances in the centres of galaxies obtained from their spectra trough the strong-line method are close to or slightly lower than the central intersect abundances estimated from the radial abundance gradient both in AGNs and Star-forming galaxies. The oxygen abundance of the NLR is usually lower than the maximum attainable abundance in galaxies (∼2 times the solar value). This suggests that there is no extraordinary chemical enrichment of the NLRs of AGNs.
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Papers by Angela Krabbe