arXiv subjects

Yara L. Jaffe

Publications and source records attributed to Yara L. Jaffe.

12 recordsLinked to original sources

arXiv2026

Characterizing the Formation and Evolution of S0-galaxies (CaFES-0): Revealing the origin of the mass-size relation for S0 galaxies

We investigate the structural evolution and formation pathways of lenticular (S0) galaxies using the Hydrangea suite of cosmological hydrodynamical simulations. Simulated galaxies reproduce the observed mass-size relation from the SAMI and MaNGA surveys, enabling a direct comparison between morphology, angular momentum, and size growth. We show that the S0 population occupies a characteristic V-shaped locus in the mass-size plane, which arises from the superposition of two physically distinct channels. Low-mass S0s are predominantly faded-formed S0s, quenched after infall into their present-day host halo and retaining the disk sizes of their star-forming progenitors. In contrast, high-mass S0s formed through mergers exhibit structural properties and size evolution similar to ellipticals, and typically quench before infall, consistent with pre-processing in group environments. By tracing their histories back to $z=1$, we find that faded-formed S0s experience minimal structural evolution after quenching, whereas merger-formed S0s grow significantly in size through dissipationless interactions. These divergent evolutionary pathways explain both the slope break and the overall scatter of the S0 mass-size relation, demonstrating that lenticular galaxies arise from multiple formation mechanisms that leave distinct structural imprints.

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arXiv2026

Caught in the web: galaxy mergers along cosmic filaments

Galaxy clusters grow through the accretion of galaxies from groups, filaments, and other clusters. During this process, galaxies may undergo pre-processing in lower-density environments, where galaxy-galaxy mergers and other interactions can significantly alter their properties prior to cluster infall. We investigate the role of galaxy mergers in the pre-processing of galaxies prior to cluster infall by studying the spatial distribution of mergers across the cosmic web. We use a sample of 43,922 galaxies targeted by the 4MOST CHANCES survey in and around 33 low-redshift clusters (z < 0.07). Using Zoobot, a deep-learning framework trained on Galaxy Zoo data, we identify 698 galaxy mergers. We measure their distances to cosmic web filaments and compare them with those of non-merging galaxies. We find that galaxy mergers are significantly closer to filaments than the non-merging galaxy population, with this trend being strongest beyond the cluster virial radius. This suggests that filaments provide conditions conducive to mergers, possibly moderating relative velocities and enhancing gas availability. Our findings support a scenario in which filaments play a key role in transforming galaxies through pre-processing by promoting mergers before they enter cluster cores where star formation quenches.

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arXiv2025

Star formation at different stages of ram-pressure stripping as observed through far-ultraviolet imaging of 13 GASP galaxies

Galaxies undergoing ram-pressure stripping develop gaseous tails that can extend several kiloparsecs outside the galaxy disc. We used far-ultraviolet and H$α$ imaging from the GASP survey to investigate how different stages of stripping affect star formation properties in the tail and disc of 13 galaxies undergoing stripping. These galaxies have different stripping strengths, as identified from the MUSE integral field spectroscopy. The star-forming knots in the disc and tails show a good correspondence between the measured FUV and H$α$ flux. This is especially true for strong and extreme cases of stripping, which have developed extended ionized gaseous tails featuring clumpy structures. The mechanism behind the H$α$ emission on the tails of these regions, which correlates well with FUV emission, is photoionization caused by young massive stars. The optical emission line ratio maps enable us to understand the emission mechanism, which can be attributed to star formation, LINER activity, or a combination of both phenomena and AGN. The star-forming regions in the emission line maps correspond well to the areas with significant FUV flux in these galaxies. Six galaxies exhibit minimal star formation in their tails, with two cases star formation is limited to the central regions and their discs are truncated. In galaxies with truncated discs, star formation is confined to a smaller region on the disc, as indicated by the FUV flux, compared to H$α$. Galaxies with strong stripping are undergoing recent star formation and are likely recent infalls. Galaxies with truncated discs confine star formation to the center, likely because they have completed a cluster crossing that depleted most of their outer gaseous disc. Galaxies with minimal FUV flux along their tails exhibit unresolved H$α$ emission which may be attributed to processes other than star formation.

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arXiv2022

A New Method to Constrain the Appearance and Disappearance of Observed Jellyfish Galaxy Tails

We present a new approach to observationally constrain where the tails of Jellyfish (JF) galaxies in groups and clusters first appear and how long they remain visible with respect to the moment of their orbital pericenter. This is accomplished by measuring the distribution of their tail directions with respect to their host's center, and their distribution in a projected velocity-radius phase-diagram. We then model these observed distributions using a fast and flexible approach where JF tails are painted onto dark matter halos according to a simple parameterised prescription, and perform a Bayesian analysis to estimate the parameters. We demonstrate the effectiveness of our approach using observational mocks, and then apply it to a known observational sample of 106 JF galaxies with radio continuum tails located inside 68 hosts such as groups and clusters. We find that, typically, the radio continuum tails become visible on first infall when the galaxy reaches roughly three quarters of r$_{200}$, and the tails remain visible for a few hundred Myr after pericenter passage. Lower mass galaxies in more massive hosts tend to form visible tails further out and their tails disappear more quickly after pericenter. We argue that this indicates they are more sensitive to ram pressure stripping. With upcoming large area surveys of JF galaxies in progress, this is a promising new method to constrain the environmental conditions in which visible JF tails exist.

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arXiv2020

GASP XXV: Neutral Hydrogen gas in the striking Jellyfish Galaxy JO204

We present JVLA-C observations of the HI gas in JO204, one of the most striking jellyfish galaxies from the GASP survey. JO204 is a massive galaxy in the low-mass cluster Abell 957 at z=0.04243. The HI map reveals an extended 90 kpc long ram-pressure stripped tail of neutral gas, stretching beyond the 30 kpc long ionized gas tail and pointing away from the cluster center. The HI mass seen in emission is (1.32 $ \pm 0.13) \times 10^{9} \rm M_{\odot}$, mostly located in the tail. The northern part of the galaxy disk has retained some HI gas, while the southern part has already been completely stripped and displaced into an extended unilateral tail. Comparing the distribution and kinematics of the neutral and ionized gas in the tail indicates a highly turbulent medium. Moreover, we observe associated HI absorption against the 11 mJy central radio continuum source with an estimated HI absorption column density of 3.2 $\times 10^{20}$ cm$^{-2}$. The absorption profile is significantly asymmetric with a wing towards higher velocities. We modelled the HI absorption by assuming that the HI and ionized gas disks have the same kinematics in front of the central continuum source, and deduced a wider absorption profile than observed. The observed asymmetric absorption profile can therefore be explained by a clumpy, rotating HI gas disk seen partially in front of the central continuum source, or by ram-pressure pushing the neutral gas towards the center of the continuum source, triggering the AGN activity.

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arXiv2019

GASP. XX. From the loose spatially-resolved to the tight global SFR-Mass relation in local spiral galaxies

Exploiting the sample of 30 local star-forming, undisturbed late-type galaxies in different environments drawn from the GAs Stripping Phenomena in galaxies with MUSE (GASP), we investigate the spatially resolved Star Formation Rate-Mass (ΣSFR-Σ_star) relation. Our analysis includes also the galaxy outskirts (up to >4 effective radii, re), a regime poorly explored by other Integral Field Spectrograph surveys. Our observational strategy allows us to detect Hα out to more than 2.7re for 75% of the sample. Considering all galaxies together, the correlation between the ΣSFR and Σ_star is quite broad, with a scatter of 0.3 dex. It gets steeper and shifts to higher Σ_star values when external spaxels are excluded and moving from less to more massive galaxies. The broadness of the overall relation suggests galaxy-by-galaxy variations. Indeed, each object is characterized by a distinct ΣSFR-Σ_star relation and in some cases the correlation is very loose. The scatter of the relation mainly arises from the existence of bright off-center star-forming knots whose ΣSFR-Σ_star relation is systematically broader than that of the diffuse component. The ΣSFR-Σtot gas (total gas surface density) relation is as broad as the ΣSFR-Σ_star relation, indicating that the surface gas density is not a primary driver of the relation. Even though a large galaxy-by-galaxy variation exists, mean ΣSFR and Σ_star values vary of at most 0.7 dex across galaxies. We investigate the relationship between the local and global SFR-M_star relation, finding that the latter is driven by the existence of the size-mass relation.

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arXiv2019

GASP. XVI. Does cosmic web enhancement turn on star formation in galaxies?

Galaxy filaments are a peculiar environment, and their impact on the galaxy properties is still controversial. Exploiting the data from the GAs Stripping Phenomena in galaxies with MUSE (GASP), we provide the first characterisation of the spatially resolved properties of galaxies embedded in filaments in the local Universe. The four galaxies we focus on show peculiar ionised gas distributions: Halpha clouds have been observed beyond four times the effective radius. The gas kinematics, metallicity map and the ratios of emission line fluxes confirm that they do belong to the galaxy gas disk, the analysis of their spectra shows that very weak stellar continuum is associated to them. Similarly, the star formation history and luminosity weighted age maps point to a recent formation of such clouds. The clouds are powered by star formation, and are characterised by intermediate values of dust absorption. We hypothesise a scenario in which the observed features are due to "Cosmic Web Enhancement": we are most likely witnessing galaxies passing through or flowing within filaments that assist the gas cooling and increase the extent of the star formation in the densest regions in the circumgalactic gas. Targeted simulations are mandatory to better understand this phenomenon.

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arXiv2018

Enhanced star formation in both disks and ram pressure stripped tails of GASP jellyfish galaxies

Exploiting the data from the GAs Stripping Phenomena in galaxies with MUSE (GASP) program, we compare the integrated Star Formation Rate- Mass relation (SFR-M_ast) relation of 42 cluster galaxies undergoing ram pressure stripping ("stripping galaxies") to that of 32 field and cluster undisturbed galaxies. Theoretical predictions have so far led to contradictory conclusions about whether ram pressure can enhance the star formation in the gas disks and tails or not and until now a statistically significant observed sample of stripping galaxies was lacking. We find that stripping galaxies occupy the upper envelope of the control sample SFR-M_ast relation, showing a systematic enhancement of the SFR at any given mass. The star formation enhancement occurs in the disk (0.2 dex), and additional star formation takes place in the tails. Our results suggest that strong ram pressure stripping events can moderately enhance the star formation also in the disk prior to gas removal.

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arXiv2017

Determining the Halo Mass Scale where Galaxies Lose Their Gas

A major question in galaxy formation is how the gas supply that fuels activity in galaxies is modulated by their environment. We use spectroscopy of a set of well characterized clusters and groups at $0.4 10.4$) of these old galaxies with weak [OII] emission. We use line ratios and compare to studies of local early type galaxies to conclude that this gas is likely excited by post-AGB stars and hence represents a diffuse gas component in the galaxies. For cluster and group galaxies the fraction with EW([OII])$>5$Å is $f_{[OII]}=0.08^{+0.03}_{-0.02}$ and $f_{[OII]}=0.06^{+0.07}_{-0.04}$ respectively. For field galaxies we find $f_{[OII]}=0.27^{+0.07}_{-0.06}$, representing a 2.8$σ$ difference between the [OII] fractions for old galaxies between the different environments. We conclude that a population of old galaxies in all environments has ionized gas that likely stems from stellar mass loss. In the field galaxies also experience gas accretion from the cosmic web and in groups and clusters these galaxies have had their gas accretion shut off by their environment. Additionally, galaxies with emission preferentially avoid the virialized region of the cluster in position-velocity space. We discuss the implications of our results, among which is that gas accretion shutoff is likely effective at group halo masses (log~${\cal M}/$\msol$>12.8$) and that there are likely multiple gas removal processes happening in dense environments.

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arXiv2015

BUDHIES II: A phase-space view of HI gas stripping and star-formation quenching in cluster galaxies

We investigate the effect of ram-pressure from the intracluster medium on the stripping of HI gas in galaxies in a massive, relaxed, X-ray bright, galaxy cluster at z=0.2 from the Blind Ultra Deep HI Environmental Survey (BUDHIES). We use cosmological simulations, and velocity vs. position phase-space diagrams to infer the orbital histories of the cluster galaxies. In particular, we embed a simple analytical description of ram-pressure stripping in the simulations to identify the regions in phase-space where galaxies are more likely to have been sufficiently stripped of their HI gas to fall below the detection limit of our survey. We find a striking agreement between the model predictions and the observed location of HI-detected and non-detected blue (late-type) galaxies in phase-space, strongly implying that ram-pressure plays a key role in the gas removal from galaxies, and that this can happen during their first infall into the cluster. However, we also find a significant number of gas-poor, red (early-type) galaxies in the infall region of the cluster that cannot easily be explained with our model of ram-pressure stripping alone. We discuss different possible additional mechanisms that could be at play, including the pre-processing of galaxies in their previous environment. Our results are strengthened by the distribution of galaxy colours (optical and UV) in phase-space, that suggests that after a (gas-rich) field galaxy falls into the cluster, it will lose its gas via ram-pressure stripping, and as it settles into the cluster, its star formation will decay until it is completely quenched. Finally, this work demonstrates the utility of phase-space diagrams to analyze the physical processes driving the evolution of cluster galaxies, in particular HI gas stripping.

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arXiv2014

Ionized gas disks in elliptical and S0 galaxies at $z<1$

We analyse the extended, ionized-gas emission of 24 early-type galaxies (ETGs) at $0<z<1$ from the ESO Distant Cluster Survey (EDisCS). We discuss different possible sources of ionization and favour star-formation as the main cause of the observed emission. 10 galaxies have disturbed gas kinematics, while 14 have rotating gas disks. In addition, 15 galaxies are in the field, while 9 are in the infall regions of clusters. This implies that, if the gas has an internal origin, this is likely stripped as the galaxies get closer to the cluster centre. If the gas instead comes from an external source, then our results suggest that this is more likely acquired outside the cluster environment, where galaxy-galaxy interactions more commonly take place. We analyse the Tully-Fisher relation of the ETGs with gas disks, and compare them to EDisCS spirals. Taking a matched range of redshifts, $M_{B}<-20$, and excluding galaxies with large velocity uncertainties, we find that, at fixed rotational velocity, ETGs are 1.7 mag fainter in $M_{B}$ than spirals. At fixed stellar mass, we also find that ETGs have systematically lower specific star-formation rates than spirals. This study constitutes an important step forward towards the understanding of the evolution of the complex ISM in ETGs by significantly extending the look-back-time baseline explored so far.

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arXiv2010

The colour-magnitude relation of Elliptical and Lenticular galaxies in the ESO Distant Cluster Survey

We study the colour-magnitude relation (CMR) for a sample of 172 morphologically-classified E/S0 cluster galaxies from the ESO Distant Cluster Survey (EDisCS) at 0.4<z<0.8. The intrinsic colour scatter about the CMR is very small (0.076) in rest-frame U-V. Only 7% of the galaxies are significantly bluer than the CMR. The scarcity of blue S0s indicates that, if they are the descendants of spirals, these were already red when they became S0s. We observe no dependence of the CMR scatter with redshift or cluster velocity dispersion. This implies that by the time cluster E/S0s achieve their morphology, the vast majority have already joined the red sequence. We estimate the galaxy formation redshift z_F for each cluster and find that it does not depend on the cluster velocity dispersion. However, z_F increases weakly with cluster redshift. This trend becomes clearer when including higher-z clusters from the literature, suggesting that, at any given z, in order to have a population of fully-formed E and S0s they needed to have formed most of their stars 2-4 Gyr prior to observation. In other words, the galaxies that already have early-type (ET) morphologies also have reasonably-old stellar populations. This is partly a manifestation of the "progenitor bias", but also a consequence of the fact that the vast majority of the ETs in clusters (in particular the massive ones) were already red by the time they achieved their morphology. E and S0 galaxies exhibit very similar colour scatter, implying similar stellar population ages. We also find that fainter ETs finished forming their stars later, consistent with the cluster red sequence being built over time and the brightest galaxies reaching the red sequence earlier than fainter ones. Finally, we find that the ET cluster galaxies must have had their star formation truncated over an extended period of at least 1 Gyr. [abridged]

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