Galaxy formation and evolution

Abstract:

We report the discovery of 31 new high- z quasars in the redshift range 6.6 < z < 7.8. These quasars were selected from approximately 3000 deg 2 of sky covered during the first 1.5 years of the Euclid Wide Survey, representing the initial results of the Euclid high- z quasar search. Our candidate selection employed multiple machine-learning and probabilistic techniques applied to the EuclidI E , Y E , J E , and H E images, supplemented by ancillary z -band data when available. Spectroscopic follow-up observations were carried out with Keck, Magellan, and the Large Binocular Telescope (LBT). Among the new discoveries, there are 12 quasars at z ≥ 7, more than doubling the number of previously known quasars at z ≥ 7. The newly discovered quasars exhibit 21.2 < J E < 23.2 (−25.5 < M 1450 < −23.6), extending quasar studies to the faint end of the quasar luminosity function (QLF) at z ≳ 7. The quasar with the highest- z , EUCL J172902.75+641018.1 at z ≈ 7.77, sets the new redshift record for the most distant quasar ever reported. These discoveries demonstrate Euclid ’s transformative role in high- z quasar discovery and set the stage for future follow-up studies of the early galaxies hosting quasars, supermassive black hole growth, and the intergalactic medium in the epoch of reionisation.

Abstract:

Context. This paper presents a detailed analysis of a gas-rich star-forming ultra-diffuse galaxy (UDG) as part of the ESO Large Programme Looking into the faintEst WIth MUSE (LEWIS). Among the UDGs in the LEWIS sample, UDG 6 is the only galaxy that hosts a significant amount of ionised gas with evidence of emission lines, suggesting recent star-forming activity. Aims. The main goal of this work is to constrain the formation history of this UDG by comparing its properties with the main formation scenarios proposed for this extreme class of galaxies. Methods. We adopted integral field spectroscopy from MUSE to derive the morphology and the structural properties of the stellar and gas components of UDG 6. We applied spectral fitting and Voronoi tessellation algorithms to the MUSE data-cube to derive the kinematics and properties of the gas and stellar component, explore gas dynamics, and characterise emission lines. Moreover, we derived the properties of the globular cluster (GC) populations by applying a multi-band spectrophotometric analysis. Results. We confirmed that UDG 6 is a member of the Hydra I cluster and that it has a systemic velocity of V sys, * ∼ 3580 km s −1 . It is characterised by a regular and elongated shape and contains a significant dust content ( A V = 1.2 ± 0.5 mag), a metal-poor (12 + log 10 (O/H) = 7.7 ± 0.2 dex) ionised gas fraction ( f gas = 0.24 ± 0.08), and an underlying old-to-intermediate (≳3 Gyr) stellar component. Evidence of local and clumpy star-forming activity has been revealed through the analysis of emission line ratios, and an arc-like tidal feature was discovered from unsharp masking analysis. The number counts of GCs in UDG 6 is N GC = 0.2 ± 5.4. Conclusions. Similar to the other UDGs in LEWIS, UDG 6 might originate from a “puffed-up dwarf” whose stellar content has been stretched out to larger radii, passively evolving into a more diffuse galaxy. Since UDG 6 is located in a dynamically active region of the cluster characterised by tidal features and stripping phenomena, we suggest that the environmental processes have played a role in shaping its properties. A tidal interaction with a nearby galaxy might have triggered recent star-formation activity without dramatically altering the coherent gas rotation in UDG 6.

Abstract:

Abstract We present soft X-ray spectroscopy of the black-hole X-ray binary V4641 Sgr with the XMM-Newton Reflection Grating Spectrometer (RGS). The RGS spectrum shows narrow emission features from N vi–vii and O vii–viii superimposed on a partially covered disk blackbody continuum. A blind Gaussian search confirms the presence of significant lines at the expected rest wavelengths. He-like triplet ratios (high G, low R) and full photoionization modelling both indicate a dense, photoionized plasma. Small redshifted velocities of ~540–720 km s−1 are suggested, which are consistent with quasi-static or slowly flowing gas away from the observer after accounting for systematics. Photoionization modelling requires two xstar components with an intermediate ionization parameter (log ξ ≃ 3.1) and a low ionization parameter (log ξ ≃ 0.36), respectively. The simultaneous EPIC-pn spectrum suggests highly ionized Fe emission structures, hinting at an additional, more highly ionized component. These results imply the existence of a radially extended, multiphase, and dense disk atmosphere in the source. We compare the source with other X-ray binaries showing similar emission lines. V4641 Sgr shares a similarly high inclination with other sources; however, the presence of low ionization emission lines distinguishes it from the rest.

Abstract:

The period between z ∼ 3-6 (`cosmic morning'), a key transformational phase in galaxy evolution preceding `cosmic noon' (z ∼ 1-3), is very poorly explored in terms of feedback from active galactic nuclei (AGN) acting through gas outflows driven by energetic radiation. In this work, we study the properties of outflows in AGN (mostly X-ray-selected) from the GOODS-S field, exploiting JWST NIRSpec IFU observations as part of the Galaxy Assembly with NIRSpec IFS (GA-NIFS) GTO survey. Together with its twin subsample from the COSMOS field reported in a previous GA-NIFS work, this constitutes the largest spatially resolved sample of AGN outflows at these redshifts to date, comprising 16 targets with outflows (out of a total of 19 AGN), and probes the unexplored regime of AGN at z ∼ 3-6 with bolometric luminosities of łbol ∼ 10^ 45-46 We mapped the rest-frame optical ionised gas emission lines (e.g. at sub-kiloparsec scales and spectrally isolated the broad wings that trace fast outflows from the gas at rest in the host galaxies. The incidence of ionised outflows in the GOODS-S + COSMOS GA-NIFS sample is high (>75%), among the highest at any redshift; however, a more homogeneous outflow detection method and sample selection would be required to draw firm conclusions on the redshift evolution of the outflow incidence. We inferred outflow velocities between ∼600--2000 ̨ms, maximum radii of łesssim1 up to ∼4 kpc, and ionised gas mass outflow rates of ∼0.1 up to ≳100 which in some cases can exceed the host galaxy star formation rate (SFR). The assumed electron density of 1000 cm -3 is conservative; lower values, as measured in some outflow studies and suggested by theory, would imply inversely proportionally higher mass outflow rates. We find that the outflow properties inferred for the GOODS-S + COSMOS GA-NIFS AGN sample and their relations to łbol and SFR generally align with those observed for other spatially resolved literature samples of AGN outflows across different redshifts and AGN luminosities. Nonetheless, after accounting for any luminosity bias, our analysis suggests a cosmic evolution of the outflow properties, with higher median mass outflow rates (and possibly also mass loading factors) at higher redshifts, especially at z>3, which indicates that AGN outflows were stronger in the early Universe than at later times, and thus potentially more capable of affecting their host galaxy.