ALBERT

Description: 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, 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 averaged 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.

Description: 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, 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 averaged 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.

Description: We have used 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 have found that, on average, the abundances obtained via infrared 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. The ionization correction factor (ICF) for the neon is obtained from direct determinations of ionic fractions using infrared emission lines. We derive a constant Ne/O ratio (log Ne/O  –0.70) for a large range of metallicities, independently of the ICF used to compute the neon total abundance.

Description: X-shooter and WHT-ISIS spectra of the star-forming galaxy PHL 293B also known as A2228-00 and SDSS J223036.79-000636.9 are presented in this paper. We find broad (FWHM = 1000 km s –1 ) and very broad (FWZI = 4000 km s –1 ) components in the Balmer lines, narrow absorption components in the Balmer series blueshifted by 800 km s –1 , previously undetected Fe ii multiplet (42) absorptions also blueshifted by 800 km s –1 , IR Ca ii triplet stellar absorptions consistent with [Fe/H] 〈 –2.0 and no broad components or blueshifted absorptions in the He i lines. Based on historical records, we found no optical variability at the 5 level of 0.02 mag between 2005 and 2013 and no optical variability at the level of 0.1 mag for the past 24 yr. The lack of variability rules out transient phenomena like luminous blue variables or Type IIn supernovae as the origin of the blueshifted absorptions of H i and Fe ii . The evidence points to either a young and dense expanding supershell or a stationary cooling wind, in both cases driven by the young cluster wind.

Description: In this paper, we derive oxygen abundance gradients from H ii regions located in 11 galaxies in eight systems of close pairs. Long-slit spectra in the range 4400–7300 Å were obtained with the Gemini Multi-Object Spectrograph at Gemini South (GMOS-S). Spatial profiles of oxygen abundance in the gaseous phase along galaxy discs were obtained using calibrations based on strong emission lines ( N 2 and O 3 N 2). We found oxygen gradients to be significantly flatter for all the studied galaxies than those in typical isolated spiral galaxies. Four objects in our sample, AM 1219A, AM 1256B, AM 2030A and AM 2030B, show a clear break in the oxygen abundance at galactocentric radius R / R 25 between 0.2 and 0.5. For AM 1219A and AM 1256B, we found negative slopes for the inner gradients, and for AM 2030B, we found a positive slope. All three cases show a flatter behaviour to the outskirts of the galaxies. For AM 2030A, we found a positive slope for the outer gradient, while the inner gradient is almost compatible with a flat behaviour. We found a decrease of star formation efficiency in the zone that corresponds to the oxygen abundance gradient break for AM 1219A and AM 2030B. For the former, a minimum in the estimated metallicities was found very close to the break zone, which could be associated with a corotation radius. However, AM 1256B and AM 2030A, present a star formation rate maximum but not an extreme oxygen abundance value. All four interacting systems that show oxygen gradient breaks have extreme SFR values located very close to break zones.The H ii regions located in close pairs of galaxies follow the same relation between the ionization parameter and the oxygen abundance as those regions in isolated galaxies.

Description: We review the results of high-dispersion spectroscopy of 17 circumnuclear star-forming regions (CNSFRs) in 3 nearby early spiral galaxies, NGC 2903, NGC 3310 and NGC 3351. We find that single-Gaussian fitting to the Hβ and [O iii ]5007 Å line profiles results in velocity dispersions around 32 and 52 km s –1 , respectively, while the IR Ca ii triplet cross-correlation technique provides stellar velocity dispersion values close to 50 km s –1 . Even though multiple kinematical components are present, the relation between gas velocity dispersion and Balmer emission line luminosity ( L – relation) reproduces the correlation for disc giant H ii regions albeit with a larger scatter. The scatter in the L – relation is considerably reduced when theoretical evolutionary corrections are applied suggesting that an age range is present in the sample of CNSFRs. To analyse the observed complex profiles, we performed multiple Gaussian component fits to the Hβ and [O iii ]5007 Å lines obtaining optimal fits with two Gaussians of different widths. These best fits indicate that the narrower component has average velocity dispersion close to 23 km s –1 while the broader component shows average values in the range 50–60 km s –1 for both lines, close to the observed stellar velocity dispersions. The fluxes of the broad and narrow Hβ components are similar. This is not the case for [O iii ]5007 Å for which the broad components have higher fluxes than the narrow ones, thus producing a clear segregation in their [O iii ]/Hβ ratios. We suggest a possible scenario for understanding the behaviour of CNSFRs in the L – and gas – * diagrams involving an inner gaseous disc responsible for the narrow component of the emission lines. Our main conclusion is that the presence of different kinematical components with similar total fluxes in the emission line spectrum of CNSFRs raises important doubts regarding the properties of the ionized gas derived from global line ratios obtained with low-resolution spectroscopy in star-forming regions in the central regions of early-type galaxies. Given the ubiquity of these star-forming systems, ionized gas analyses should be done preferably from high-dispersion spectra with high spatial resolution.

Description: 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 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 )  –0.8 for some objects in the range 1.5 〈 z 〈 3 is derived.

Description: Integral field spectroscopy is presented for star-forming regions in M33. A central area of 300  x 500 pc 2 and the external H ii region IC 132, at a galactocentric distance ~19 arcmin (4.69 kpc), were observed with the Potsdam Multi-Aperture Spectrophotometer instrument at the 3.5-m telescope of the Centro Astronómico Hispano–Alemán (CAHA, aka Calar Alto Observatory). The spectral coverage goes from 3600 Å to 1 μm to include from [O ii ] 3727 Å to the near-infrared lines required for deriving sulphur electron temperature and abundance diagnostics. Local conditions within individual H ii regions are presented in the form of emission-line fluxes and physical conditions for each spatial resolution element (spaxel) and for segments with similar Hα surface brightness. A clear dichotomy is observed when comparing the central to outer disc H ii regions. While the external H ii region has higher electron temperature plus larger Hβ equivalent width, size and excitation, the central region has higher extinction and metal content. The dichotomy extends to the Baldwin–Phillips–Terlevich (BPT) diagnostic diagrams that show two orthogonal broad distributions of points. By comparing with pseudo-3D photoionization models, we conclude that the bulk of observed differences are probably related to a different ionization parameter and metallicity. Wolf–Rayet (WR) features are detected in IC 132, and resolved into two concentrations whose integrated spectra were used to estimate the characteristic number of WR stars. No WR features were detected in the central H ii regions despite their higher metallicity.

Description: We present an observational study about the impacts of the interactions on the electron density of H ii regions located in seven systems of interacting galaxies. The data consist of long-slit spectra in the range 4400–7300 Å, obtained with the Gemini Multi-Object Spectrograph at Gemini South (GMOS-S). The electron density was determined using the ratio of emission lines [S ii ] 6716/6731. Our results indicate that the electron density estimates obtained of H ii regions from our sample of interacting galaxies are systematically higher than those derived for isolated galaxies. The mean electron density values of interacting galaxies are in the range of N e  = 24–532 cm –3 , while those obtained for isolated galaxies are in the range of N e  = 40–137 cm –3 . Comparing the observed emission lines with predictions of photoionization models, we verified that almost all the H ii regions of the galaxies AM 1054A, AM 2058B and AM 2306B have emission lines excited by shock gas. For the remaining galaxies, only few H ii regions have emission lines excited by shocks, such as in AM 2322B (one point) and AM 2322A (four points). No correlation is obtained between the presence of shocks and electron densities. Indeed, the highest electron density values found in our sample do not belong to the objects with gas shock excitation. We emphasize the importance of considering these quantities especially when the metallicity is derived for these types of systems.