arXiv subjects

Blessing Musiimenta

Publications and source records attributed to Blessing Musiimenta.

8 recordsLinked to original sources

arXiv2026

HYPERION. The cold ISM of rapidly growing $z>6$ quasars: diverse gas reservoirs, dust enrichment, and feedback signatures

Luminous QSOs at $z>6$ host some of the most rapidly assembled SMBHs in the early Universe. Characterizing their cold ISM is essential to determine their evolution. We investigate the molecular gas, cold dust, star formation, gas-to-dust ratio, and ionized ISM of ten HYPERION QSOs using new ALMA Band 3 observations targeting CO(6-5) and the underlying $\sim100$ GHz continuum, complemented by archival and literature ALMA/NOEMA data. We detect $\sim100$ GHz continuum emission in eight targets and CO(6-5) emission in four QSO hosts, J025-33, J083+11, J231-20, and J0252-0503, as well as in the companion of J231-20. The inferred molecular gas masses are of order $10^{10}~M_\odot$, while the non-detections imply upper limits of a few $10^9~M_\odot$, indicating a broad range of molecular reservoirs within the HYPERION population. For J025-33 and J083+11, the FIR SEDs are well sampled and yield low dust temperatures, $T_{\rm dust}=36^{+13}_{-7}$ K and $32^{+4}_{-3}$ K, respectively, well below the average value for $z>6$ QSOs. Combining gas and dust masses, we find a gas-to-dust ratio for J083+11, ${\rm GDR}=16^{+5}_{-4}$, among the lowest measured in a high-redshift QSO host. We also detect [NII]$\lambda 205\,\mu$m emission in J025-33 and tentatively in J083+11, suggesting dense or highly structured ionized gas. Finally, we identify a tentative connection among $T_{\rm dust}$, the X-ray photon index $\Gamma$, and the C IV velocity shift. These trends may indicate that more powerful winds redistribute dust away from the central AGN heating source, lowering its temperature and weakening the connection between the large-scale dust reservoir and the X-ray corona. Overall, HYPERION QSOs emerge as a heterogeneous population in which SMBH growth, star formation, gas consumption, enrichment, and feedback are not necessarily synchronized.

astro-ph.GA↗

arXiv2026

CIV wind properties of the SDSS-V X-ray selected quasars: strong optical-to-UV emission is key regardless of X-ray strength

We present an investigation of the rest-frame optical/UV and X-ray properties for a sample of 3027 X-ray selected quasars between $1.5 \leq z \leq 3.5$ detected in the deepest Spectrum Roentgen Gamma/eROSITA data available and observed by the fifth iteration of the Sloan Digital Sky Survey (SDSS-V). We parametrize the CIV$\lambda1549$ emission line to infer the strength of accretion disc winds and perform X-ray spectral fitting. The X-ray spectral properties -- namely, the 2keV monochromatic luminosity (L$_\text{2keV}$) and spectral slope -- are not strongly correlated with wind strength. Despite this result, the X-ray selected sample is shifted towards lower CIV blueshifts and higher equivalent widths than the optically selected sample observed in previous SDSS surveys, and matching in optical luminosity, redshift, and Eddington ratio does not reduce these differences. We estimate the far-UV luminosity using the HeII$\lambda1640$ line luminosity and define the slopes between this and the 2500A monochromatic luminosity ($L_{2500}$) and L$_\text{2keV}$ ($\alpha_\text{ouv}$ and $\alpha_\text{uvx}$, respectively) in a similar manner to the familiar $\alpha_\text{ox}$ parameter, which tracks the spectral slope between $L_{2500}$ and L$_\text{2keV}$. The quantity $\alpha_\text{ouv}$ is more strongly correlated with wind strength in our sample than $\alpha_\text{ox}$. We show that the correlation between $\alpha_\text{ox}$ and wind strength is driven by the relationship between the optical luminosity and wind strength. Our results are consistent with a radiation line-driven wind, whereby the ionising far-UV photons must not over-ionise the gas. The hard X-ray photons are few enough in number to have a negligible effect on the ionisation state of the material.

astro-ph.GA↗

arXiv2025

The eROSITA Final Equatorial Depth Survey (eFEDS): SDSS spectroscopic observations of X-ray sources

We present one of the largest uniform optical spectroscopic surveys of X-ray selected sources to date that were observed as a pilot study for the Black Hole Mapper (BHM) survey. The BHM program of the Sloan Digital Sky Survey (SDSS)-V is designed to provide optical spectra for hundreds of thousands of X-ray selected sources from the SRG/eROSITA all-sky survey. This significantly improves our ability to classify and characterise the physical properties of large statistical populations of X-ray emitting objects. Our sample consists of 13079 sources in the eROSITA eFEDS performance verification field, 12011 of which provide reliable redshifts from 0 6.5x10^-15 erg/s/cm^2) and were observed for about 20 years with fibre-fed SDSS spectrographs. After including all available redshift information for the eFEDS sources from the dedicated SDSS-V plate programme and archival data, we visually inspected the SDSS optical spectra to verify the reliability of these redshift measurements and the performance of the SDSS pipeline. The visual inspection allowed us to recover reliable redshifts (for 99% of the spectra with a signal-to-noise ratio of >2) and to assign classes to the sources, and we confirm that the vast majority of our sample consists of active galactic nuclei (AGNs). Only ~3% of the eFEDS/SDSS sources are Galactic objects. We also show the diversity of the optical spectra of the X-ray selected AGNs and provide spectral stacks with a high signal-to-noise ratio in various sub-samples with different redshift and optical broad-band colours. Our AGN sample contains optical spectra of (broad-line) quasars, narrow-line galaxies, and optically passive galaxies. It is considerably diverse in its colours and in its levels of nuclear obscuration.

astro-ph.HE↗

arXiv2024

Accretion properties of X-ray AGN: Evidence for radiation-regulated obscuration with redshift-dependent host galaxy contribution

We adopt a Bayesian X-ray spectral approach to investigate the accretion properties of unobscured ($20<\log(N_{\rm H}/{\rm cm}^{-2}<22$) and obscured ($22< \log(N_{\rm H}/{\rm cm}^{-2}<24$) active galactic nuclei (AGN) to shed light on the orientation vs evolution scenarios for the origin of the obscuring material. For a sample of 3882 X-ray-selected AGN from the {\it Chandra} COSMOS Legacy, AEGIS and CDFS extragalactic surveys, we constrain their stellar masses, $M_\star$, intrinsic X-ray luminosities, $L_{\rm X}$, obscuring column densities, $N_{\rm H}$, and specific accretion rates $\lambda\propto L_{\rm X}/M_\star$. By combining these observables within a Bayesian non-parametric approach, we infer, for the first time, the specific accretion rate distribution (SARD) of obscured and unobscured AGN to $z\approx3$, i.e. the probability of a galaxy with mass $M_\star$ at redshift $z$ hosting an AGN with column density $N_{\rm H}$ and specific accretion rate $\lambda$. Our findings indicate that (1) both obscured and unobscured SARDs share similar shapes, shifting towards higher accretion rates with redshift, (2) unobscured SARDs exhibit a systematic offset towards higher $\lambda$ compared to obscured SARD for all redshift intervals, (3) the obscured AGN fraction declines sharply at $\log\lambda_{\rm break} \sim-2$ for $z <0.5$, but shifts to higher $\lambda$ values with increasing redshift, (4) the incidence of AGN within the theoretically unstable blow-out region of the $\lambda-N_{\rm H}$ plane increases with redshift. These observations provide compelling evidence for AGN "downsizing" and radiation-regulated nuclear-scale obscuration with an increasing host galaxy contribution towards higher redshifts.

astro-ph.GA↗

arXiv2024

Ionised AGN outflows in the Goldfish galaxy -- The illuminating and interacting red quasar eFEDSJ091157.4+014327 at z $\sim$ 0.6

Evolutionary models suggest that the initial growth phases of active galactic nuclei (AGN) are dust-enshrouded, and characterised by jet/wind outflows that should gradually clear the interstellar medium (ISM) in the host by heating and/or expelling the surrounding gas. eFEDSJ091157.4$+$014327 (z$\sim$0.6) was selected from X-ray samples for its characteristics that are similar to sources with outflows which include red, obscured and X-ray luminous. We aim to explore the environment around this red quasar and characterise kinematics within the system. We used spatially resolved spectroscopic data from Multi Unit Spectroscopic Explorer (MUSE) with an average seeing of 0.6" to construct flux, velocity and velocity dispersions maps. We found that the quasar is embedded in an interacting and merging system with three other galaxies $\sim$ 50 kpc from its nucleus. Spatially resolved kinematics reveal that the quasar has extended ionised outflows of up to 9.2 kpc with positive and negative velocities up to 1000 km s$^{-1}$ and -1200 km s$^{-1}$, respectively. The velocity dispersion (W$_{80}$) ranges from 600-1800 km s$^{-1}$. We associate the presence of turbulent and high-velocity components with the outflow. The total mass outflow rate is estimated to be $\sim$ 10 M$_{\odot}$ yr$^{-1}$ and kinetic power of 2x10$^{42}$ erg s$^{-1}$. The kinetic coupling efficiencies range from 0.01%-0.03% and the momentum boosts are $\sim$ 0.2. These low values indicate that the ionised outflow is not energetically relevant. These values don't align with the theoretical predictions of both radiation-pressure-driven outflows and energy-conserving mechanisms. However, note that our results are based only on the ionised phase while theoretical predictions are multiphase. Moreover, the mass loading factor of $\sim$ 5 is an indication that these outflows are more likely AGN-driven than star formation-driven.

astro-ph.GA↗

arXiv2023

A new discovery space opened by eROSITA: Ionised AGN outflows from X-ray selected samples

In the context of an evolutionary model, the outflow phase of an Active Galactic Nuclei (AGN) occurs at the peak of its activity, once the central SMBH is massive enough to generate sufficient power to counterbalance the potential well of the host galaxy. This phase plays a vital role in galaxy evolution. We aim to apply various selection methods to isolate powerful AGNs in the feedback phase, trace and characterise their outflows, and explore the link between AGN luminosity and outflow properties. We applied a combination of methods to the eROSITA Final Equatorial Depth survey (eFEDS) catalogue and isolated ~1400 candidates at z>0.5 out of ~11750 AGNs (~12\%). We tested the robustness of our selection on the small subsample of 50 sources with available good quality SDSS spectra at 0.5 1\%. We find that the majority of the outflows have momentum flux ratios lower than 20 which rules out an energy-conserving nature. Our present work points to the unequivocal existence of a rather short AGN outflow phase, paving the way towards a new avenue to dissect AGN outflows in large samples within eROSITA and beyond.

astro-ph.GA↗

arXiv2020

A search for new $\gamma$-ray blazars from infrared selected candidates

We present a systematic study of gamma-ray blazar candidates based on a sample of 40 objects taken from the WIBR catalogue. By using a likelihood analysis, 26 of the 40 sources showed significant gamma-ray signatures $\geq3\sigma$. Using high-energy test statistics (TS) maps, we confirm 8 sources, which are completely new, and show another 15 promising $\gamma$-ray candidates. The results from this analysis show that a multi-frequency approach can help to improve the current description of the gamma-ray sky.

astro-ph.HE↗

arXiv2020

Extreme & High Synchrotron Peak Blazars beyond 4FGL: The 2BIGB $\rm γ$-ray catalogue

This paper presents the results of a $\rm γ$-ray likelihood analysis over all the extreme and high synchrotron peak blazars (EHSP & HSP) from the 3HSP catalogue. We investigate 2013 multifrequency positions under the eyes of Fermi Large Area Telescope, considering 11 years of observations in the energy range between 500 MeV to 500 GeV, which results in 1160 $\rm γ$-ray signatures detected down to the TS = 9 threshold. The detections include 235 additional sources concerning the Fermi Large Area Telescope Fourth Source Catalog (4FGL), all confirmed via high-energy TS maps, and represent an improvement of ~25% for the number of EHSP & HSP currently described in $\rm γ$-rays. We build the $\rm γ$-ray spectral energy distribution for all the 1160 2BIGB sources, plot the corresponding $\rm γ$-ray logN-logS, and measure their total contribution to the extragalactic gamma-ray background, which reaches up to ~33% at 100 GeV. Also, we show that the $\rm γ$-ray detectability improves according to the synchrotron peak flux as represented by the Figure of Merit (FOM) parameter, and note that the search for TeV peaked blazars may benefit from considering HSP and EHSP as a whole, instead of EHSPs only. The 2BIGB acronym stands for `Second Brazil-ICRANet Gamma-ray Blazars' catalogue, and all the broadband models and spectral energy distribution data-points will be available on public data repositories (OpenUniverse, GitHub, and Brazilian Science Data Center-BSDC)

astro-ph.HE↗