Author: Adriano Fontana

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THE GROWTH OF GALAXIES IN THE EARLY UNIVERSE – IX: THE PHYSICS OF EARLY GALAXIES – Sexten, Italy, January 22-26, 2024

https://www.sexten-cfa.eu/event/ggeuix/

This workshop is a chance to discuss the nature and evolution of high redshift galaxies, from cosmic noon to re-ionization, as derived from a variety of observational evidence collected across the whole electromagnetic spectrum, and theoretical investigations.

In the tradition of the previous meetings we aim at bringing together members of the main extragalactic surveys and theorists to present their latest results and perspectives for the next future.

The workshop will be a chance to discuss the major questions on the ground, that will be address in specific sessions:

  • What drove the apparently accelerated early evolution of galaxy UV luminosity and mass, especially prior to z~10?
  • What was the primary early growth mechanism of supermassive black holes, and what is the role of the resulting active galactic nuclei (AGNs) in early galaxy evolution? Can we discriminate between different avenues for black hole formation and growth, and if not how can we in the future?
  • What was the evolution of the inter-galactic medium (IGM), and how does the evolving IGM affect the observations?Are we able to track the interplay between the early evolvution of galaxies and the IGM in a meaningful and self-consistent way
  • How did metals form in early galaxies, and what can we learn about galaxy formation from different abundance patterns
  • How well can we establish metal abundances in the young Universe with existing data?
  • How and when did dust form in early galaxies? How did it affect star formation, and how/when is it subsequently destroyed within, consumed by, or ejected from the evolving host galaxy?
  • Which quenching mechanisms were most effective as a function of galaxy properties, environment, and cosmic epoch. What are the key signatures of quenching on the evolving galaxy population?
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Cosmic archaeology with massive stellar black hole binaries

The existence of massive stellar black hole binaries (MBHBs), with primary black hole (BH) masses ≥ 31 Mo, was proven by the detection of the gravitational wave (GW) event GW150914 during the first LIGO/Virgo observing run (O1), and successively confirmed by seven additional GW signals discovered in the O1 and 02 data. By adopting the galaxy formation model GAMESH coupled with binary population synthesis (BPS) calculations, here we investigate the origin of these MBHBs by selecting simulated binaries compatible in mass and coalescence redshifts. We find that their cosmic birth rates peak in the redshift range 6.5 < 2 < 10, regardless of the adopted BPS.
These MBHBs are then old systems forming in low-metallicity (Z~ [0.01-0.1] Zo), low-stellar-mass galaxies, before the end of cosmic reionization, i.e. significantly beyond the peak of cosmic star formation. GW signals generated by coalescing MBHBs open up new possibilities to probe the nature of stellar populations in remote galaxies, at present too faint to be detected by available electromagnetic facilities.

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The KMOS Lens-Amplified Spectroscopic Survey (KLASS): kinematics and clumpiness of low-mass galaxies at cosmic noon

We present results from the KMOS Lens-Amplified Spectroscopic Survey (KLASS), an ESO Very Large Telescope (VLT) large program using gravitational lensing to study the spatially resolved kinematics of 44 star-forming galaxies at 0.6 < z < 2.3 with a stellar mass of 8.1 < log(M⋆/M☉) < 11.0. These galaxies are located behind six galaxy clusters selected from the Hubble Space Telescope Grism Lens-Amplified Survey from Space (GLASS). We find that the majority of the galaxies show a rotating disc, but most of the rotation-dominated galaxies only have a low υ rot/σ0 ratio (median of υrot/σ0 ∼ 2.5). We explore the Tully-Fisher relation by adopting the circular velocity, $V_{\mathrm{ circ}}=(\upsilon _{\mathrm{ rot}}^2+3.4\sigma _0^2)^{1/2}$ , to account for pressure support. We find that our sample follows a Tully-Fisher relation with a positive zero-point offset of +0.18 dex compared to the local relation, consistent with more gas-rich galaxies that still have to convert most of their gas into stars. We find a strong correlation between the velocity dispersion and stellar mass in the KLASS sample. When combining our data to other surveys from the literature, we see an increase of the velocity dispersion with stellar mass at all redshift. We obtain an increase of υrot/σ0 with stellar mass at 0.5 < z < 1.0. This could indicate that massive galaxies settle into regular rotating discs before the low-mass galaxies. For higher redshift (z > 1), we find a weak increase or flat trend. We find no clear trend between the rest-frame UV clumpiness and the velocity dispersion and υrot/σ0. This could suggest that the kinematic properties of galaxies evolve after the clumps formed in the galaxy disc or that the clumps can form in different physical conditions.

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A comparative analysis of denoising algorithms for extragalactic imaging surveys

We present a comprehensive analysis of the performance of noise-reduction (denoising) algorithms to determine whether they provide advantages in source detection, mitigating noise on extragalactic survey images. 
The methods we analyze here are representative of different algorithmic families: Perona-Malik filtering, bilateral filter, total variation denoising, structure-texture image decomposition, non-local means, wavelets, and block-matching We tested the algorithms on simulated images of extragalactic fields with resolution and depth typical of the Hubble, Spitzer, and Euclid Space Telescopes, and of ground-based instruments. After choosing their best internal parameters configuration, we assessed their performance as a function of resolution, background level, and image type, in addition to testing their ability to preserve the objects fluxes and shapes. Finally, we analyze, in terms of completeness and purity, the catalogs that were extracted after applying denoising algorithms on a simulated Euclid Wide Survey VIS image and on real H160 and K-band (HAWK-I) observations of the CANDELS GOODS-South field. 
Denoising algorithms often outperform the standard approach of filtering with the point spread function (PSF) of the image. Applying structure-texture image decomposition, Perona-Malik filtering, the total variation method by Chambolle, and bilateral filtering on the Euclid-VIS image, we obtain catalogs that are both more pure and complete by 0.2 magnitude than those based on the standard approach. The same result is achieved with the structure-texture image decomposition algorithm applied on the H160 image. The relative advantage of denoising techniques with respect to PSF filtering rises with increasing depth. Moreover, these techniques better preserve the shape of the detected objects with respect to PSF smoothing. 
Conclusions: Denoising algorithms provide significant improvements in the detection of faint objects and enhance the scientific return of current and future extragalactic surveys. We identify the most promising denoising algorithms among the 20 techniques considered in this study.