arXiv subjects

D. Zakharova

Publications and source records attributed to D. Zakharova.

6 recordsLinked to original sources

arXiv2026

Virgo Filaments VII: MeerKAT HI-imaging of the VirgoIII filament

We present MeerKAT HI observations of galaxies in the nearby Virgo III filament. At a median distance of $\sim30$ Mpc, the filament extends over $\approx16$ Mpc across $\sim56$ deg$^2$. Our survey comprises 15 targeted MeerKAT pointings centred on HI deficient galaxies. Multi-resolution HI imaging at 8-90 arcsec with an rms of $\sim0.3$ mJy beam$^{-1}$ reaches column densities of $\sim4\times10^{20}$ to $\sim4\times10^{18}$ atoms cm$^{-2}$. This probes HI in galaxy discs at $\sim1.2$ kpc resolution and their outskirts at $\sim13.5$ kpc. We detect HI emission from 80 sources within the 500-3000 km/s range; most are optically detected galaxies, while 10 per cent lack confirmed counterparts. We also identify three HI clouds without optical counterparts near an interacting system, possibly displaced during the interaction. Galaxies in the filament lie below the field HI gas-fraction scaling relations at fixed stellar mass. Crucially, $\sim40$ per cent of galaxies not selected for HI deficiency fall more than $1σ$ below these relations, with an even greater fraction lying under the mean relation itself, indicating that the low HI gas fractions are widespread in the filament rather than confined to the pre-selected deficient population. Quantifying HI morphologies using an asymmetry parameter, we find a wide range of disturbances without a clear trend with projected distance to the filament spine or local density, suggesting a combination of local interactions and the filament itself. This paper presents the survey description, catalogue, and HI atlas enabling investigations of gas removal mechanisms in Virgo III galaxies.

astro-ph.GA↗

arXiv2026

Virgo Filaments VI: H$α$ clumps in the filaments around the Virgo galaxy cluster

It is still not clear which environmental processes operate in filaments. Given the ubiquity of filaments and their importance in feeding clusters, a proper understanding of these mechanisms is crucial to a more complete picture of galaxy evolution. To investigate them, we need large galaxy samples with spatially resolved information. As part of this effort, we analyse resolved H$α$ maps of 685 galaxies inside and outside the filaments around the Virgo cluster in addition to extensive measurements of integrated physical properties. We create a pipeline to decompose the H$α$ images into individual clumps that trace star forming regions. We find that the number and average size of clumps in a galaxy are well-defined functions of distance and angular resolution. In particular, the power-law relation between the number of clumps and the distance of a galaxy is consistent with a fractal structure of star forming regions. We formulate an algorithm to compare filament and non-filament galaxies after removing observational differences. Although we do not have any conclusive evidence for a difference in clump size distributions between filament and non-filament galaxies, we do find that filament galaxies have slightly more peripheral clumps than their non-filament counterparts.

astro-ph.GA↗

arXiv2025

Environmental history of filament galaxies: stellar mass assembly and star-formation of filament galaxies

Galaxy properties correlate with their position within the cosmic web. While galaxies are observed in an environment today, they may have experienced different environments in the past. The environmental history, linked to pre-processing, leaves an imprint on the properties of galaxies. We use the GAEA semi-analytic model and IllustrisTNG to reconstruct the environmental histories of galaxies between $z=0$ and $z=4$ that today reside in filaments. Our goal is to understand how galaxy properties are related to their past environments, and the role of the cosmic web in shaping their properties. We find that filament galaxies at $z=0$ are a heterogeneous mix of populations with distinct environmental histories. The vast majority of them have experienced group processing, with only $\sim$20\% remaining centrals throughout their life. For $\rm 9 < \log_{10}(M_{star}/M_{sun}) < 10$ galaxies, models confirm that the environmental effects are primarily driven by group processing: satellites stop growing stellar mass and exhibit elevated quenched fractions, whereas filament galaxies remain centrals have properties that are similar to field galaxies. Massive galaxies ($\rm \log_{10}(M_{star}/M_{sun}) > 10$) that have never been satellites and entered filaments more than 9 Gyr ago show accelerated stellar mass assembly and higher quenched fractions relative to the field, due to a higher frequency of merger events inside filaments, even at fixed mass. The most massive $\rm \log ((M_{star} / M_{sun}) > 11$) galaxies accreted onto filaments over 9 Gyr ago, highlighting the role of filaments in building up the high-mass end of the galaxy population. Filaments regulate galaxy evolution in a mass-dependent way: group environments regulate low-mass galaxies, while filaments favour the growth of massive galaxies.

astro-ph.GA↗

arXiv2024

The impact of large-scale structure on the anisotropic quenching of satellites

Galaxies within groups exhibit characteristics different from those of galaxies that reside in regions of average density (the field). Galaxy properties also depend on their location within the host structure and orientation with respect to the central galaxy: galaxies in the inner regions that are aligned to the major axis of the central galaxy tend to be more quenched and redder than galaxies in the outskirts and with random orientation. This phenomenon, called anisotropic satellite galaxy quenching (ASGQ), can be explained in two different ways: invoking either external influences (large-scale distribution of matter) or internal factors (black hole activity of the central galaxy). In this work, we study the impact of filaments in shaping the ASGQ in the local Universe, exploiting the magneto-hydrodynamic (MHD) simulation IllustrisTNG. We separated all surviving satellites into young and old populations depending on their infall times. We show that only young satellites contribute to the observed ASGQ. These satellites preferentially infall along the major axis of the central galaxy, which tends to have the same direction of the filament feeding the groups. We demonstrate that old satellites were quenched inside their hosts and do not exhibit signatures of ASGQ. We show that the ASGQ emerges at the time of the infall of the young satellites and is also visible outside $\rm R_{200}$. In contrast, there is no sign of anisotropic distribution in the inner regions ($R<0.5 R_{200}$). We argue that our results support a scenario in which a large-scale structure is imprinted on the ASGQ.

astro-ph.GA↗

arXiv2024

Seven wonders of Cosmic Dawn: JWST confirms a high abundance of galaxies and AGNs at z $\simeq$ 9-11 in the GLASS field

We present JWST/NIRSpec PRISM follow-up of candidate galaxies at z=9-11 selected from deep JWST/NIRCam photometry in GLASS-JWST Early Release Science data. We spectroscopically confirm six sources with secure redshifts at z = 9.52-10.43, each showing multiple emission lines. An additional object is likely at z = 10.66, based on its Lya-break and a single emission feature, while one source is a lower redshift interloper. The sample includes the first JWST-detected candidate at z=10, GHZ1/GLASS-z10, which we confirm at z = 9.875, and the X-ray detected AGN GHZ9 confirmed at z = 10.145. Three objects in our sample, including GHZ9, have EW(CIII])>20A and occupy a region compatible with AGN emission in the EW(CIII]) vs CIV/CIII] diagram. The spectroscopic sample confirms a high abundance of galaxies at z > 9. We measure a number density of z=10 galaxies in the GLASS-JWST ERS field that is a factor of >3 higher than other JWST-based estimates at demagnified rest-frame magnitudes of -21 < Muv < -19. We find that the positions of these galaxies in redshift and angular space are not consistent with all of them being part of a unique progenitor of present-day galaxy clusters. The high density of objects in the GLASS region can be explained either by clustering on large scales or by a superposition of different forming structures of which we observe only the brightest members. By considering all the spectroscopic z=10 sources in the Abell-2744 field, we identify two potential galaxy proto-clusters centered around GHZ9 and JD1, with relative separations between their members of 1-2 pMpc. The potential AGN nature of three of the sources in our sample lends support to a scenario in which the high abundance of bright sources determined by JWST surveys at cosmic dawn may be affected by AGN contribution to their UV luminosity.

astro-ph.GA↗

arXiv2024

Virgo Filaments. III. The gas content of galaxies in filaments as predicted by the GAEA semi-analytic model

Galaxy evolution depends on the environment in which galaxies are located. The various physical processes (ram-pressure stripping, tidal interactions, etc.) that can affect the gas content in galaxies have different efficiencies in different environments. In this work, we examine the gas (atomic \ce{HI} and molecular \ce{H2}) content of local galaxies inside and outside clusters, groups, and filaments as well as in isolation using observational and simulated data. We exploited a catalog of galaxies in the Virgo cluster(including the surrounding filaments) and compared the data against the predictions of the Galaxy Evolution and Assembly(GAEA) semi-analytic model, which has explicit prescriptions for partitioning the cold gas content in its atomic and molecular phases. We extracted from the model a mock catalog that mimics the observational biases and one not tailored to observations to study the impact of observational limits on the results and predict trends in regimes not covered by the current observations. The observations and simulated data show that galaxies within filaments exhibit intermediate cold gas content between galaxies in clusters and isolation. The amount of \ce{HI} is typically more sensitive to the environment than \ce{H2} and low-mass galaxies ($\log_{10} [{\rm M}_{\star} / \rm{M}_{\sun} ] < 10$) are typically more affected than their massive ($\log_{10} [{\rm M}_{\star} / \rm{M}_{\sun} ] > 10$) counterparts. Considering only model data, we identified two distinct populations among filament galaxies present in similar proportions: those simultaneously lying in groups and isolated galaxies. The former has properties more similar to cluster and group galaxies, and the latter is more similar to those of field galaxies. We therefore did not detect filaments' strong effects on galaxies' gas content, and we ascribe the results to the presence of groups in filaments.

astro-ph.GA↗