arXiv subjects

Angela C. Krabbe

Publications and source records attributed to Angela C. Krabbe.

9 recordsLinked to original sources

arXiv2026

AstroInspect: a web-based system to organize, assess, and visually inspect astronomical objects

The rapid growth of imaging and spectroscopic surveys has intensified the need for efficient tools that support visual inspection, a practice that remains essential for tasks such as classification, catalog refinement, and validation of automated methods. Existing solutions, however, often require the use of multiple platforms and complex workflows to integrate heterogeneous data. To address this challenge, we present the first release of the AstroInspect (https://astroinspect.github.io), a web-based system which ensures seamless access to several astronomical resources. The system provides an intuitive graphical user interface (GUI) through which users can upload catalogs of objects defined by celestial coordinates. AstroInspect automatically enriches these catalogs with complementary information, including imaging, spectroscopic, and photometric data retrieved in real time from surveys such as the Sloan Digital Sky Survey (SDSS), the Legacy Surveys (LS), and the Southern Photometric Local Universe Survey (S-PLUS). As an example of its scientific utility, we used AstroInspect to identify H$\alpha$ emission-line galaxies within a 7 deg radius in the direction of the Hydra I cluster (also known as Abell 1060) by visual inspection. Using a candidate set of 981 galaxies selected from S-PLUS photometric data, we produced a catalog of 80 galaxies with confirmed H$\alpha$ emission. These results highlight the potential of AstroInspect to support efficient visual inspection workflows.

astro-ph.IM↗

arXiv2026

The First Detection of Forbidden Emission Lines at the Outskirts of the AGN Broad Line Region?

Double-peaked (DP) broad emission line profiles in active galactic nuclei (AGNs) are often interpreted as signatures of rotating disk-like structures in the broad-line region (BLR) and are commonly observed in low-luminosity AGNs using recombination lines. We use optical spectroscopy to investigate the origin of double-peaked broad emission line profiles observed not only in hydrogen recombination lines but also in forbidden transitions in the LINER galaxy IC 1459. We detected DP emission in all strong optical lines except for the [S II] doublet, which has the lowest critical density among all the lines. We successfully fitted the DP broad profiles using a disk-like BLR model, assuming a circular accretion disk with an inclination of approximately 35 degrees and internal turbulence of about 500 km/s, confined within a maximum radius of 9.6 (+4.8, -1.1) light-years. We estimate a full width at half maximum of the DP profiles of about 3300 km/s. Our results provide new insights into the structure of the BLR, indicating that forbidden emission lines can be produced in lower-density regions near the outskirts of the BLR.

astro-ph.GA↗

arXiv2025

The S-PLUS 12-band photometry as a powerful tool for discovery and classification: ten cataclysmic variables in a proof-of-concept study

Multi-band photometric surveys provide a straightforward way to discover and classify astrophysical objects systematically, enabling the study of a large number of targets at relatively low cost. Here we introduce an alternative approach to select Accreting White Dwarf (AWD) candidates following their spectral energy distribution, entirely supported by the twelve photometric bands of the Southern Photometric Local Universe Survey (S-PLUS). The method was validated with optical spectroscopic follow-up with the Gemini South telescope which unambiguously established ten systems as cataclysmic variables (CVs), alongside Swift X-ray observations of four of them. Among the ten CVs presented here are those that may be low-luminosity intermediate polars or WZ Sge-type dwarf novae with rare outbursts, two subclasses that can be easily missed in time-domain and X-ray surveys, the two methods currently dominating the discovery of new CVs. Our approach based on S-PLUS provides an important, complementary tool to uncover the total population of CVs and the complete set of its subclasses, which is an important step towards a full understanding of close binary evolution, including the origin of magnetic fields in white dwarfs and the physics of accretion. Finally, we highlight the potential of S-PLUS beyond AWDs, serving other surveys in the characterization of their sources.

astro-ph.SR↗

arXiv2024

Determining star formation rates in AGN hosts from strong optical emission lines

The influence of Active Galactic Nuclei (AGN) on star formation within their host galaxies remains a topic of intense debate. One of the primary challenges in quantifying the star formation rate (SFR) within AGN hosts arises from the prevalent assumption in most methodologies, which attribute gas excitation to young stars alone. However, this assumption does not consider the contribution of the AGN to the ionization of the gas in their environment. To address this issue, we evaluate the use of strong optical emission lines to obtain the SFR surface density ($Σ{\rm SFR_{AGN}}$) in regions predominantly ionized by an AGN, using a sample of 293 AGN hosts from the MaNGA survey, with SFR measurements available through stellar population fitting. We propose calibrations involving the H$α$ and [O\,{\sc iii}]$λ$5007 emission lines, which can be used to determine $Σ{\rm SFR_{AGN}}$, resulting in values consistent with those estimated through stellar population fitting.

astro-ph.GA↗

arXiv2024

A study of interacting galaxies from the Arp-Madore Catalogue: Triggering of star formation and nuclear activity

We present Gemini Multi-Object Spectrograph (GMOS) spectroscopic observations of 95 galaxies from the Arp & Madore (1987) catalogue of peculiar galaxies. These galaxies have been selected because they appear to be in pairs and small groups. These observations have allowed us to confirm that 60 galaxies are indeed interacting systems. For the confirmed interacting sample, we have built a matched control sample of isolated galaxies. We present an analysis of the stellar populations and nuclear activity in the interacting galaxies and compare them with the isolated galaxies. We find a median light (mass) fraction of 55% (10%) in the interacting galaxies coming from stellar populations younger than 2 Gyr and 28% (3%) in the case of the isolated galaxies. More than half of the interacting galaxies are dominated by this young stellar population, while the isolated ones have most of their light coming from older stellar populations. We used a combination of diagnostic diagrams (BPTs and WHAN) to classify the main ionization mechanisms of the gas. The interacting galaxies in our sample consistently show a higher fraction of active galactic nuclei (AGN) relative to the control sample, which ranges between 1.6 and 4 depending on the combination of diagnostic diagrams employed to classify the galaxies and the number of galaxies considered. Our study provides further observational evidence that interactions drive star formation and nuclear activity in galaxies and can have a significant impact on galaxy evolution.

astro-ph.GA↗

arXiv2023

Oxygen abundances in the narrow line regions of Seyfert galaxies and the metallicity-luminosity relation

We present oxygen abundances relative to hydrogen (O/H) in the narrow line regions (NLRs) gas phases of Seyferts 1 (Sy 1s) and Seyferts 2 (Sy 2s) Active Galactic Nuclei (AGNs). We used fluxes of the optical narrow emission line intensities [$3\,500<λ($Å$)<7\,000$] of 561 Seyfert nuclei in the local universe ($z\lesssim0.31$) from the second catalog and data release (DR2) of the BAT AGN Spectroscopic Survey, which focuses on the \textit{Swift}-BAT hard X-ray ($\gtrsim10$ keV) detected AGNs. We derived O/H from relative intensities of the emission lines via the strong-line methods. We find that the AGN O/H abundances are related to their hosts stellar masses and that they follow a downward redshift evolution. The derived O/H together with the hard X-ray luminosity ($L_{\rm X}$) were used to study the X-ray luminosity-metallicity ($L_{\rm X}$-$Z_{\rm NLR}$) relation for the first time in Seyfert galaxies. In contrast to the broad-line focused ($L_{\rm X}$-$Z_{\rm BLR}$) studies, we find that the $L_{\rm X}$-$Z_{\rm NLR}$ exhibit significant anti-correlations with the Eddington ratio ($λ_{\rm Edd}$) and these correlations vary with redshifts. This result indicates that the low-luminous AGNs are more actively undergoing Interstellar Medium (ISM) enrichment through star formation in comparison with the more luminous X-ray sources. Our results suggest that the AGN is somehow driving the galaxy chemical enrichment, as a result of the inflow of pristine gas that is diluting the metal rich gas, together with a recent cessation on the circumnuclear star-formation.

astro-ph.GA↗

arXiv2014

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.

astro-ph.GA↗

arXiv2013

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.

astro-ph.CO↗

arXiv2012

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]λ1.2570 μm/Paβ vs. H2λ2.1218 μm/Brγ 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.

astro-ph.CO↗