arXiv subjects

Paloma Guetzoyan

Publications and source records attributed to Paloma Guetzoyan.

7 recordsLinked to original sources

arXiv2026

The Twentieth Data Release of the Sloan Digital Sky Survey: First All-Sky BOSS Spectra, eROSITA-SDSS-V Mapper Coordinated Observations, and a Preview of the Local Volume Mapper

This paper presents the twentieth data release (DR20) from the Sloan Digital Sky Survey, the third data release of its fifth generation (SDSS-V). SDSS-V is a panoptic spectroscopy survey that is mapping the stars, gas, and galaxies through three scientific programs: the Milky Way Mapper (MWM), the Local Volume Mapper (LVM), and the Black Hole Mapper (BHM). DR20 presents the first optical (BOSS) SDSS-V spectra from southern hemisphere for the MWM and BHM surveys; new optical MWM and BHM data from the northern hemisphere are also available, for a total over 3 million spectra of 1.5 million stars and half a million galaxies and quasars, with galactic and extragalactic x-ray targets coordinate with eROSITA DR2. DR20 includes integral field spectroscopy maps from LVM of six targets and 169 tiles, spanning Galactic HII regions, planetary nebulae, and nearby galaxies. Additionally, eighteen value added catalogs are also released with DR20, based on SDSS-V MWM and BHM data, and we present a new LVM visualization tool including an RGB HiPS map as a value added product.

astro-ph.GA↗

arXiv2026

Spectroscopic Analysis of Fermi-detected Blazars using SDSS-V

The automated spectroscopic pipeline of the Sloan Digital Sky Survey (SDSS) systematically assigns Galactic star, galaxy, or typical quasar classifications to jet-dominated blazars, owing to the absence of a non-thermal jet continuum component in its template library. In this study, we present a new, physically motivated, multi-component spectral fitting pipeline that we apply to 746 optical counterparts of Fermi/4FGL-DR4 $γ$-ray sources in the SDSS-V Data Release 20 spectroscopic database, yielding 707 well-fitted blazar candidates dominated by Power-law+Galaxy (59.4%), Power-law+Lines (22.6%), and Power-law+QSO (15.0%) model families. Independent WISE infrared (IR) photometry confirms that 96.6% of the 88 sources originally misclassified as Galactic stars by SDSS fall within the canonical blazar region, with 90.9% reclassified as BL Lacertae object (BL Lac) candidates, demonstrating the success of our new pipeline. The new classification scheme naturally recovers the known cosmological separation between BL Lac and Flat Spectrum Radio Quasar (FSRQ) candidates and a separation of approximately one order of magnitude in median $γ$-ray luminosity. We compare our redshift estimates to a validation sample of 111 sources in the Third Fermi-LAT Catalogue of High-Energy Sources (3FHL), finding a 10.4% reduction in catastrophic failures ($η= 0.387$ vs 0.432) over the SDSS pipeline. The equivalent width analysis validates the traditional |EW| = 5 Ang classification boundary at the population level (BL Lac: 4.47 $\pm$ 0.15 Ang; FSRQ: 22.86 $\pm$ 0.86 Ang), although 49.5% of individual BL Lac candidates exceed this threshold and 51.4% show simultaneous emission and absorption features. This hybrid population challenges the traditional binary blazar classification and points towards a more physically continuous description of blazar properties.

astro-ph.HE↗

arXiv2026

SDSS-V: Revealing a weak accretion state in X-ray selected red quasars

Red quasars (rQSOs) have been recognized as a short-lived, early stage in the evolutionary cycle of Active Galactic Nuclei (AGN), with fundamental differences in their intrinsic properties compared to blue quasars (bQSOs). In this work, we present the first large X-ray sample of 380 rQSOs, selected from the eROSITA/SDSS-V collaboration, providing uniform X-ray detection with optical spectroscopy accros half the sky, in the German hemisphere of eROSITA. We combine X-ray imaging, optical spectroscopy, and multi-wavelength photometry to fully probe the accretion, absorption and host properties of rQSOs. Independent Component Analysis is used to reconstruct optical spectra in a data-driven and non-parametric approach, while accounting for dust reddening and host contamination. rQSOs are intrinsically X-ray weak compared to bQSOs, with a higher fraction found at low X-ray luminosities (over 50$\%$ of the rQSO sample have $L_X < 10^{43.5} \, \rm erg \, s^{-1}$). We investigate the relative X-ray strength of rQSOs by measuring the spectral slope indicator $α_{OX}$. Despite their suppressed X-ray emission, rQSOs are not optically faint, but show low $α_{OX}$ values, indicating weak X-ray emission relative to their bright optical continua. X-ray spectral measurements reveal large gas column densities relative to optical reddening due to dust, implying that X-ray absorption could arise from dust-free gas close to the supermassive Black Hole (BH) rather than a classical dusty torus, while the dust responsible for optical reddening likely resides on larger host-galaxy scales or is associated with dusty gas carried in disc winds. rQSOs trace a phase of suppressed BH assembly relative to stellar mass growth, suggesting that they represent a distinct evolutionary stage where BH accretion is suppressed while the host galaxy continues to grow.

astro-ph.GA↗

arXiv2025

The Nineteenth Data Release of the Sloan Digital Sky Survey

Mapping the local and distant Universe is key to our understanding of it. For decades, the Sloan Digital Sky Survey (SDSS) has made a concerted effort to map millions of celestial objects to constrain the physical processes that govern our Universe. The most recent and fifth generation of SDSS (SDSS-V) is organized into three scientific ``mappers". Milky Way Mapper (MWM) that aims to chart the various components of the Milky Way and constrain its formation and assembly, Black Hole Mapper (BHM), which focuses on understanding supermassive black holes in distant galaxies across the Universe, and Local Volume Mapper (LVM), which uses integral field spectroscopy to map the ionized interstellar medium in the local group. This paper describes and outlines the scope and content for the nineteenth data release (DR19) of SDSS and the most substantial to date in SDSS-V. DR19 is the first to contain data from all three mappers. Additionally, we also describe nine value added catalogs (VACs) that enhance the science that can be conducted with the SDSS-V data. Finally, we discuss how to access SDSS DR19 and provide illustrative examples and tutorials.

astro-ph.GA↗

arXiv2024

Large-scale dual AGN in large-scale cosmological hydrodynamical simulations

Detecting dual active galactic nuclei (DAGN) in observations and understanding theoretically which massive black holes (MBHs) compose them and in which galactic and large-scale environment they reside are becoming increasingly important questions as we enter the multi-messenger era of MBH astronomy. This paper presents the abundance and properties of DAGN produced in nine large-scale cosmological hydrodynamical simulations. We focus on DAGN powered by AGN with Lbol > 1e43 erg/s and belonging to distinct galaxies, i.e. pairs that can be characterised with current and near-future electromagnetic observations. We find that the number density of DAGN separated by a few to 30 proper kpc varies from 1e-8 (or none) to 1e-3 comoving Mpc^3 in the redshift range z=0-7. At a given redshift, the densities of the DAGN numbers vary by up to two orders of magnitude from one simulation to another. However, for all simulations, the DAGN peak is in the range z=1-3, right before the peak of cosmic star formation or cosmic AGN activity. The corresponding fractions of DAGN (with respect to the total number of AGN) range from 0 to 6 percent. We find that simulations could produce too few DAGN at z=0 (or merge pairs too quickly) compared to current observational constraints while being consistent with preliminary constraints at high redshift (z = 3). Next-generation observatories (e.g., AXIS) will be of paramount importance to detect DAGN across cosmic times. We predict the detectability of DAGN with future X-ray telescopes and discuss DAGN as progenitors for future LISA gravitational wave detections.

astro-ph.CO↗

arXiv2024

X-ray AGN in Boötes: The lack of growth of the most massive black holes since z=4

Supermassive Black Holes (BHs) are known to efficiently grow through gas accretion, but even sustained and intense mass build-up through this mechanism struggles to explain the assembly of the most massive BHs observed in the local Universe. Using the Chandra Deep-Wide Field Survey (CDFWS) in the Boötes field, we measure BH--galaxy assembly in massive galaxies ($M_\star\gtrsim10^{10}\rm M_\odot$) through the AGN fraction and specific Black Hole accretion rate (sBHAR) distribution as a function of redshift and stellar mass. We determine stellar masses and star formation rates for a parent sample of optically selected galaxies as well as those with X-ray detections indicating the presence of an AGN through Spectral Energy Distribution (SED) fitting. We derive a redshift-dependent mass completeness limit and extract X-ray information for every galaxy as to provide a comprehensive picture of the AGN population in massive galaxies. While X-ray AGN samples are dominated by moderately massive host galaxies of $M_{\star} \geqslant 10^{10}\rm M_{\odot}$, we do not find a strong stellar mass dependence in AGN fraction (to limits in sBHAR), indicating a bias towards massive galaxies in the observed samples. We derive BH-galaxy growth tracks over time, which reveal that while most BH mass has been accumulated since $z=4$ for lower mass BHs, the assembly of the most massive BHs is more complex, with little to no relative mass gain since $z=4$, implying that rapid and intense growth episodes prior to $z=4$ were necessary to form these massive BHs.

astro-ph.GA↗

arXiv2023

VLT/MUSE Characterisation of Dimorphos Ejecta from the DART Impact

We have observed the Didymos-Dimorphos binary system with the MUSE integral field unit spectrograph mounted at the Very Large Telescope (VLT) pre and post-DART impact, and captured the ensuing ejecta cone, debris cloud, and tails at sub-arcsecond resolutions. We targeted the Didymos system over 11 nights from 26 September to 25 October 2022, and utilized both narrow and wide-field observations with and without adaptive optics, respectively. We took advantage of the spectral-spatial coupled measurements and produced both white-light images and spectral maps of the dust reflectance. We identified and characterized numerous dust features, such as the ejecta cone, spirals, wings, clumps, and tails. We found that the base of the Sunward edge of the wings, from 03 to 19 October, consistent with maximum grain sizes on the order of 0.05-0.2 mm, and that the earliest detected clumps have the highest velocities on the order of 10 m/s. We also see that three clumps in narrow-field mode (8x8'') exhibit redder colors and slower speeds, around 0.09 m/s, than the surrounding ejecta, likely indicating that the clump is comprised of larger, slower grains. We measured the properties of the primary tail, and resolved and measured the properties of the secondary tail earlier than any other published study, with first retrieval on 03 October. Both tails exhibit similarities in curvature and relative flux, however, the secondary tail appears thinner, which may be caused by lower energy ejecta and possibly a low energy formation mechanism such as secondary impacts.

astro-ph.EP↗