arXiv subjects

Przemysław Nowaczyk

Publications and source records attributed to Przemysław Nowaczyk.

4 recordsLinked to original sources

arXiv2026

Little Red Dots host Black Hole Stars: A unified family of gas-reddened AGN revealed by JWST/NIRSpec spectroscopy

We use the DAWN JWST Archive to construct and characterise a sample of 146 little red dots (LRDs) across 2.0<z<9.3, selecting all sources with v-shaped UV-optical continua from NIRSpec/PRISM spectra and compact morphologies in NIRCam/F444W imaging. We show that LRD continuum spectra are ubiquitously well described by modified blackbodies across ~$0.4-1.0μ$m, with typical T~5000K or $λ_{peak}$~$0.65μ$m across 2 dex in luminosity, and a tail toward T~2000K. LRDs therefore trace a locus in the Hertzsprung-Russell diagram that is directly analogous to stars on the Hayashi track, strongly supporting the picture that LRDs are AGN embedded in optically-thick dense gas envelopes. Hotter LRDs with $λ_{peak}<0.65μ$m typically have strong Balmer breaks, redder UV slopes and high optical luminosities; other LRDs show weak or no Balmer breaks, and wide variety in $β_{UV}$ and $L_{5100}$. Crucially, we demonstrate that the UV-optical continuum shapes and luminosities are strongly linked to the $Hα,\ Hβ$, [OIII] and OI line properties. There is a tight linear relation between the H$α$ and optical continuum luminosities, as well as H$α$ and OI$_{8446}$, indicating that Balmer, OI and optical emission must primarily be powered by the same source. The Balmer decrement increases strongly toward higher $L_{Hα}$, $L_{5100}$ and Balmer break strength, providing key evidence for luminosity-dependent effects of collisional (de-)excitation and resonant scattering in the gaseous envelopes. In contrast, we show that [OIII] emission likely originates from star-forming host galaxies, and that its strong correlation with Balmer break strength arises naturally from variation in the AGN-to-host ratio among the LRD population. Our work presents an empirical description of the nature and structure of LRDs, defining a new benchmark for ongoing LRD model developments.

astro-ph.GA↗

arXiv2026

Atomic gas properties at the positions of supernovae Type Ia, II, and Ib/c

Understanding which stars explode as which type of supernovae (SNe) is crucial to measure their contribution to the metal production and feedback halting star formation. Most of the studies of the gas in the environment of SNe are limited by a small sample size ($<10$). The goal of this paper is to present the first analysis of atomic gas properties at the positions of a statistically significant sample of SNe in order to constrain their nature. We selected 133 SNe (29 Ia, 77 II, 27 Ib/c) which have exploded in galaxies with existing atomic gas data. In order to test whether SN positions trace enhancements in the atomic gas distribution, we analyzed the fraction of pixels on the {\hi} map which are fainter than the pixel in which SN is located and the fraction of the {\hi} flux contributed by these pixels. All types of SNe deviate from the completely random distribution. From the three types of SNe, Type II showed the largest offset from the {\hi} distribution, preferring even higher concentrations of atomic gas. This type of SNe deviated also from being proportional to the stellar surface density of the host. The results are, however, complicated by the limits of the survey in size, and in the un-even resolution of the {\hi} observations. Furthermore, by direct comparison between the three SN types, we observed that the distributions of these populations are still consistent with each other. The obtained results fail to ascertain that Ib/c core-collapse SNe, and possibly also Type II SNe, are connected with the densest concentrations of atomic gas in their hosts, unlike what has been suggested for GRBs and Ic-BL SNe. Hence, the birth of progenitors of Type II and Ib/c SNe is still consistent with being connected with the current star formation in their hosts, whereas the progenitors of GRBs and Type Ic-BL SNe require more special conditions to form, for example low metallicity.

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arXiv2024

Evolution of the star formation rate surface density main sequence. Insights from a semi-analytic simulation since $z = 12$

Recent high-redshift ($z>4$) spatially resolved observations with the James Webb Space Telesescope have shown the evolution of the star formation rate (SFR) surface density ($Σ_{\rm SFR}$) and its main sequence in the $Σ_{\rm SFR}$-$M_*$ diagram ($Σ_{\rm SFR}{\rm MS}$). The $Σ_{\rm SFR}{\rm MS}$\ is already observed at cosmic morning ($z\sim7.5$). The use of $Σ_{\rm SFR}$\ is physically motivated because it is normalized by the area in which the star formation occurs, and this indirectly considers the gas density. The $Σ_{\rm SFR}$-$M_*$ diagram has been shown to complement the widely used (specific) SFR-$M_*$, particularly when selecting passive galaxies. We establish the $Σ_{\rm SFR}$\ evolution since $z=12$ in the framework of the L-Galaxies2020 semi-analytical model (SAM), and we interpret recent observations. We estimated $Σ_{\rm SFR}$(-$M_*$) and the cosmic star formation rate density (CSFRD) for the simulated galaxy population and for the subsamples, which were divided into stellar mass bins in the given redshift. The simulated $Σ_{\rm SFR}$\ decreases by $\sim3.5$ dex from $z=12$ to $z=0$. We show that galaxies with different stellar masses have different paths of $Σ_{\rm SFR}$\ evolution. We find that $Σ_{\rm SFR}{\rm MS}$\ is already observed at $z\sim11$. The simulated $Σ_{\rm SFR}{\rm MS}$\ agrees with the observed one at $z=0, 1, 2, 5$, and $7.5$ and with individual galaxies at $z>10$. We show that the highest $Σ_{\rm SFR}{\rm MS}$\ slope of $0.709\pm0.005$ is at $z\sim3$ and decreases to $\sim0.085\pm0.003$ at $z=0$. This is mostly driven by a rapid decrease in SFR with an additional size increase for the most massive galaxies in this redshift range. This coincides with the dominance of the most massive galaxies in the CSFRD from the SAM.

astro-ph.GA↗

arXiv2024

The fate of the interstellar medium in early-type galaxies. IV. The impact of stellar feedback, mergers, and black holes on the cold ISM in simulated galaxies

Removing cold interstellar medium (ISM) from a galaxy is central to quenching star formation. However, the exact mechanism of this process remains unclear. The objective of this work is to find the mechanism responsible for dust and gas removal in simulated early-type galaxies (ETGs). A statistically significant sample of massive (M_*>$10^{10}$M$_\odot$), simulated ETG in a redshift range of 0.02--0.32 is studied in the context of its ISM properties. In particular, we investigate the cold dust and gas removal timescales, the cold gas inflows, and their relation with black hole (BH) mass. We also investigate the evolution of galaxies in the dust vs. star formation rate (SFR) plane and the influence of merger events. We find agreement with previous observational works considering the timescales of dust and HI removal from ETGs. When considering the dust-to-stellar mass ratio as a function of time in simulations, we recovered a similar decline as in the observational sample as a function of stellar age, validating its use for timing the ISM decline. Moreover, we recover the observed relation between dust mass and SFR for actively star-forming galaxies as well as for passive ETGs. We also show that starburst galaxies form their own sequence on the dust vs. SFR plot in a form $\log(M_{\rm dust, SB})= 0.913\times \log({\rm SFR}) + 6.533$ with $2σ$ scatter of 0.32. Finally, we find that type II supernova reverse shocks dominate the dust destruction at the early stages of ETG evolution, while at later times stellar feedback becomes more important. We show that merger events lead to morphological transformations by increasing the bulge-to-total stellar mass ratio followed by an increase in BH masses. The BH feedback resulting from radio mode accretion prevents the hot halo gas from cooling, indirectly leading to a decrease in the SFR.

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