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Starburstiness (R SB ) of jellyfish galaxies as a function of cluster velocity dispersion (σ v,cl ; left), the ICM density (ρ ICM ; middle), and the degree of ram pressure (P ram ; right). Error bars in the left panel represent standard deviations of starburstiness of jellyfish galaxies in the same host clusters. We plot the data of jellyfish samples with strong RPS signatures as described in Figure 3. The Spearman's rank correlation coefficients are shown at the top of each panel.
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Jellyfish galaxies are an excellent tool to investigate the short-term effects of ram pressure stripping (RPS) on star formation in cluster environments. It has been thought that the star formation activity of jellyfish galaxies may depend on the host-cluster properties, but previous studies have not yet found a clear correlation. In this study, we...
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... estimate the value of the starburstiness (R SB ) of the jellyfish galaxies, defined as the ratio between the specific star formation rate (sSFR) of a galaxy to that of the SFMS at the same redshift, indicative of relative star formation activity with respect to the normal galaxies ( Elbaz et al. 2011). Figure 5 illustrates the starburstiness of the jellyfish galaxies as a function of the host-cluster velocity dispersion (left panel), the ICM density (middle panel), and the strength of ram pressure (right panel). For all the panels, we plot the starburstiness of our sample (star symbols) in addition to the GASP (circles), RO19 (diamonds), and EK19 (triangles) sample with a strong RPS signature (JClass >3) This selection allows us to compare the star formation activity of jellyfish galaxies with similar morphological classes. ...
Citations
... IGM-ISM interactions in galaxies primarily result in the removal, occurring on time-cales of ∼1-2 × 10 9 yr (Lotz et al. 2019 ), of both the cold atomic gas in the discs and the surrounding hotter gas reservoir (strangulation), leading to an o v erall outside-in reduction in star formation activity and a potential localized increase in the MNRAS 528, 3260-3280 (2024) SFR at the ISM-IGM interface, with the complete transformation into an S0 necessitating of a subsequent galaxy-wide structural rearrangement induced either externally or by the sweeping gas itself (Lee et al. 2022 ). While the gravitational field of massive galaxies may be strong enough to retain some neutral gas in their central regions or to reaccrete a certain fraction of the displaced ISM, in small galaxies the stripping of the H I may be total and irreversible, which may accelerate their transition to quiescence (see Boselli, Fossati & Sun 2022 and references therein). ...
Spatially resolved MaNGA’s optical spectra of 1072 present-day lenticular (S0) galaxies, dimensionally reduced from a principal component analysis (PCA), are used to determine their radial activity structure shaped by any possible nebular ionization source. Activity profiles within 1.5 Re are examined in tandem with the mass, age, ellipticity and kinematics of the stars, as well as environmental density. Among the results of this comparison, we find that the sign of the radial activity gradient of S0s is tightly related to their PCA classification, BPT designation, and star formation status. PCA-passive lenticulars often show low-level, flat activity profiles, although there is also a significant number of systems with positive gradients, while their less common active counterparts generally have negative gradients, usually associated with high SSFRs and, sometimes, moderate Seyfert emission. A fraction of the latter also shows radial activity profiles with positive gradients, which become more abundant with increasing stellar mass regardless of environmental density. Our analysis also reveals that the subset of active S0s with negative gradients experiences at all galactocentric radii a systematic reduction in its median activity level with stellar mass, consistent with expectations for main sequence galaxies. In contrast, passive S0s with positive gradients show the opposite behaviour. Furthermore, systems whose activity is dominated by star formation are structurally rounder than the rest of S0s, while those classified as Seyfert exhibit higher rotational support. The possibility that negative and positive activity gradients in S0s may result from rejuvenation by two distinct types of minor mergers is raised.
... It is true that some studies focussing on nearby clusters have shown direct evidence of ram-pressure stripping (Vollmer et al. 2008Zabel et al. 2019;Moretti et al. 2020), but they disagree on its impact on the molecular gas content. This is partially because, before cluster galaxies begin to lose molecular gas, they may gain it due to, for instance, momentary compression of galactic gas by the ram pressure (Fujita & Nagashima 1999;Kronberger et al. 2008;Kapferer et al. 2009;Bekki 2014;Henderson & Bekki 2016;Mok et al. 2016;Steinhauser et al. 2016;Lee et al. 2017;Ramos-Martínez et al. 2018;Vulcani et al. 2018;Safarzadeh & Loeb 2019;Troncoso-Iribarren et al. 2020;Roberts et al. 2021;Lee et al. 2022). On long timescales, however, the molecular gas content is expected to reduce. ...
We employ the EAGLE hydrodynamical simulation to uncover the relationship between cluster environment and H2 content of star-forming galaxies at redshifts spanning 0≤z≤1. To do so, we divide the star-forming sample into those that are bound to clusters and those that are not. We find that, at any given redshift, the galaxies in clusters generally have less H2 than their non-cluster counterparts with the same stellar mass (corresponding to an offset of ≲0.5 dex), but this offset varies with stellar mass and is virtually absent at M⋆≲10^9.3 M⊙. The H2 deficit in star-forming cluster galaxies can be traced back to a decline in their H2 content that commenced after first infall into a cluster, which occurred later than a typical cluster galaxy. Evolution of the full cluster population after infall is generally consistent with 'slow-then-rapid' quenching, but galaxies with M⋆≲10^9.5 M⊙ exhibit rapid quenching. Unlike most cluster galaxies, star-forming ones were not pre-processed in groups prior to being accreted by clusters. For both of these cluster samples, the star formation efficiency remained oblivious to the infall. We track the particles associated with star-forming cluster galaxies and attribute the drop in H2 mass after infall to poor replenishment, depletion due to star formation, and stripping of H2 in cluster environments. These results provide predictions for future surveys, along with support and theoretical insights for existing molecular gas observations that suggest there is less H2 in cluster galaxies.
... On the other hand, extreme stripping leads to full quenching and significant reddening (Steinhauser et al. 2016), depending on the mass of the galaxy and the particular configuration of the orbit in the given group or cluster (Bekki 2014). From an observational perspective, Poggianti et al. (2016), working with a sample of local jellyfish galaxies, found that stripping candidates tend to be located above the general population of galaxies in the star formation rate−stellar mass relation, indicating a star formation rate (SFR) excess, and Vulcani et al. (2018) identified enhanced star formation in the disks of the ram-pressure affected galaxies, in addition to the star formation taking place in the tails (see also Lee et al. 2022 for the dependence of the star formation activity on the host-cluster properties). These results indicate that the ram pressure exerted by the hot ICM is an effective mechanism to trigger star formation in perturbed disk galaxies, a mechanism that needs to be taken into consideration when exploring internal processes that regulate the star formation activity. ...
Stellar bars have been found to substantially influence the properties of stellar populations in galaxies, affecting their ability to form stars. While this can be easily seen when studying galaxies in relatively isolated environments, such type of analysis requires a higher degree of complexity when cluster galaxies are considered, due to the variety of interactions that can potentially occur in these denser environments. We use IFU MUSE data from the GASP survey to study the combined effect of the presence of a stellar bar and ram pressure, on spatially resolved properties of stellar populations. We have analyzed spatially resolved indicators of both recent star formation rates (SFRs) and average stellar population ages to check for signatures of anomalous central star formation activity, also taking into account the possible presence of nuclear activity. We found an increase in central SFR in ram-pressure-affected galaxies when compared with unperturbed ones. The most extreme cases of increased SFR and central rejuvenation occur in barred galaxies that are at advanced stages of ram pressure stripping. For low-mass barred galaxies affected by ram pressure, the combined effect is the systematic enhancement of the star formation activity as opposed to the case of high-mass galaxies, which present both enhancement and suppression. Barred galaxies that present suppression of their star formation activity also present signatures of nuclear activity. Our results indicate that the combined effect of the presence of a bar and strong perturbation by ram pressure is able to trigger the central star formation activity and probably ignite nuclear activity.
... Additionally, Vulcani et al. (2020) find evidence for enhanced star formation at all galactocentric radii within the disks of galaxies undergoing RPS from the GAs Stripping Phenomena in galaxies sample. More broadly this work is also consistent with the fact that, on a population level, galaxies undergoing RPS have integrated SFRs that are sytematically enhanced (e.g., Dressler & Gunn 1983;Ebeling et al. 2014;Vulcani et al. 2018;Roberts & Parker 2020;Vulcani et al. 2020;Wang et al. 2020;Roberts et al. 2021b;Durret et al. 2021;Lee et al. 2022c). Based on the results of this work it is likely that these enhanced integrated SFRs are being primarily driven by star formation activity on the leading side. ...
With Mapping Nearby Galaxies at APO integral field spectroscopy, we present a resolved analysis of star formation for 29 jellyfish galaxies in nearby clusters, identified from radio continuum imaging taken by the Low Frequency Array. Simulations predict enhanced star formation on the “leading half” (LH) of galaxies undergoing ram pressure stripping, and in this work we report observational evidence for this elevated star formation. The dividing line (through the galaxy center) that maximizes this star formation enhancement is systematically tied to the observed direction of the ram-pressure-stripped tail, suggesting a physical connection between ram pressure and this star formation enhancement. We also present a case study on the distribution of molecular gas in one jellyfish galaxy from our sample, IC3949, using Atacama Large Millimeter/submillimeter Array CO J = 1 − 0, HCN J = 1 − 0, and HCO ⁺ J = 1 − 0 observations from the ALMA MaNGA Quenching and Star Formation Survey. The H 2 depletion time (as traced by CO) in IC3949 ranges from ∼1 Gyr in the outskirts of the molecular gas disk to ∼11 Gyr near the galaxy center. IC3949 shows a clear region of enhanced star formation on the LH of the galaxy where the average depletion time is ∼2.7 Gyr, in line with the median value for the galaxy on the whole. Dense gas tracers, HCN and HCO ⁺ , are only detected at the galaxy center and on the LH of IC3949. Our results favor a scenario in which ram pressure compresses the interstellar medium, promoting the formation of molecular gas that in turn fuels a localized increase of star formation.
... We carry out emission-line analyses of the GMOS/IFU data of jellyfish galaxies, which includes the Hα line. Using the Hα-derived SFRs of jellyfish galaxies in this study, Lee et al. (2022) presented a relation between the star formation activity of the jellyfish galaxies and the host cluster properties. In this paper, we present detailed methods and analyses of emission lines of the jellyfish galaxies. ...
... In addition, the median SFR fraction in the tail is also much higher in this study ( f SFR = 22%) than in the GASP studies ( f SFR = 3%). Lee et al. (2022) presented a detailed comparison of the star formation activity of the five jellyfish galaxies in this study with that of other known jellyfish galaxies including the GASP sample, considering galaxy stellar mass, redshift, and jellyfish morphology. As a result, they suggested a positive correlation between the star formation activity of jellyfish galaxies and the host cluster properties. ...
... We display the projected phase-space diagrams of our targets and the GASP jellyfish galaxies (Gullieuszik et al. 2020) by categorizing the sample based on stellar mass ( Figure 12) and host cluster velocity dispersion (Figure 13). Lee et al. (2022) showed the phase-space diagrams of the jellyfish galaxies with different categories of jellyfish morphology. We plot the 2D clustercentric distance normalized by the virial radius of the host cluster (R cl /R 200 ) on the x-axis, and we plot the velocity relative to the cluster normalized by the cluster velocity dispersion (|Δv los |/σ v,cl ) on the y-axis. ...
Jellyfish galaxies are an intriguing snapshot of galaxies undergoing ram pressure stripping (RPS) in dense environments, showing spectacular star-forming knots in their disks and tails. We study the ionized gas properties of five jellyfish galaxies in massive clusters with Gemini GMOS/Integral Field Unit observations: MACSJ0916-JFG1 ( z = 0.330), MACSJ1752-JFG2 ( z = 0.353), A2744-F0083 ( z = 0.303), MACSJ1258-JFG1 ( z = 0.342), and MACSJ1720-JFG1 ( z = 0.383). “Baldwin, Phillips, and Terlevich” diagrams show that star formation, active galactic nuclei (AGNs), or mixed effects are ionizing gas in these galaxies. Radial velocity distributions of ionized gas seem to follow disk rotation of galaxies, with the appearance of a few high-velocity components in the tails as a sign of RPS. Mean gas velocity dispersion is lower than 50 km s ⁻¹ in most star-forming regions except near AGNs or shock-heated regions, indicating that the ionized gas is dynamically cold. Integrated star formation rates (SFRs) of these galaxies range from 7 M ⊙ yr ⁻¹ to 35 M ⊙ yr ⁻¹ , and the tail SFRs are from 0.6 M ⊙ yr ⁻¹ to 16 M ⊙ yr ⁻¹ , which are much higher than those of other jellyfish galaxies in the local universe. These high SFR values imply that RPS triggers intense star formation activity in these extreme jellyfish galaxies. The phase-space diagrams demonstrate that the jellyfish galaxies with higher stellar masses and higher host cluster velocity dispersion are likely to have more enhanced star formation activity. The jellyfish galaxies in this study have similar gas kinematics and dynamical states to those in the local universe, but they show a much higher SFR.
... We carry out emission line analyses of the GMOS/IFU data of jellyfish galaxies, which includes the Hα line. Using the Hα-derived SFRs of jellyfish galaxies in this study, Lee et al. (2022) presented a relation between the star formation activity of the jellyfish galaxies and the host cluster properties. In this paper, we present the detailed methods and analyses of emission lines of the jellyfish galaxies. ...
... In addition, the median SFR fraction in the tail is also much higher in this study (f SFR = 22%) than in the GASP studies (f SFR = 3%). Lee et al. (2022) presented a detailed comparison of the star formation activity of the five jellyfish galaxies in this study with that of other known jellyfish galaxies including the GASP sample, considering galaxy stellar mass, redshift, and jellyfish morphology. As a result, they suggested a positive correlation between the star formation activity of jellyfish galaxies and the host cluster properties. ...
... sample based on stellar mass ( Figure 12) and host cluster velocity dispersion ( Figure 13). Lee et al. (2022) showed the phase-space diagrams of the jellyfish galaxies with different categories of jellyfish morphology. We plot the 2D clustercentric distance normalized by the virial radius of the host cluster (R cl /R 200 ) on the x-axis, and we plot the velocity relative to the cluster normalized by the cluster velocity dispersion (|∆v los |/σ v,cl ) on the y-axis. ...
Jellyfish galaxies are an intriguing snapshot of galaxies undergoing ram-pressure stripping (RPS) in dense environments, showing spectacular star-forming knots in their disks and tails. We study the ionized gas properties of five jellyfish galaxies in massive clusters with Gemini GMOS/IFU observations: MACSJ0916-JFG1 ($z=0.330$), MACSJ1752-JFG2 ($z=0.353$), A2744-F0083 ($z=0.303$), MACSJ1258-JFG1 ($z=0.342$), and MACSJ1720-JFG1 ($z=0.383$). BPT diagrams show that various mechanisms (star formation, AGN, or mixed effects) are ionizing gas in these galaxies. Radial velocity distributions of ionized gas seem to follow disk rotation of galaxies, with the appearance of a few high-velocity components in the tails as a sign of RPS. Mean gas velocity dispersion is lower than 50 \kms~in most star-forming regions except near AGNs or shock-heated regions, indicating that the ionized gas %in these star-forming regions is dynamically cold. Integrated star formation rates (SFRs) of these galaxies range from $7~{\rm M_{\odot}~{\rm yr^{-1}}}$ to $35~{\rm M_{\odot}~{\rm yr^{-1}}}$ and the tail SFRs are from $0.6~{\rm M_{\odot}~{\rm yr^{-1}}}$ to $16~{\rm M_{\odot}~{\rm yr^{-1}}}$, which are much higher than those of other jellyfish galaxies in the local universe. These high SFR values imply that RPS triggers intense star formation activity in these extreme jellyfish galaxies. The phase-space diagrams demonstrate that the jellyfish galaxies with higher stellar masses and higher host cluster velocity dispersion are likely to have more enhanced star formation activity. The jellyfish galaxies in this study have similar gas kinematics and dynamical states to those in the local universe, but they show a much higher SFR.
Ram-pressure stripping (RPS) is the mechanism most often invoked to explain the observed differences between cluster and field galaxies. In the local Universe, its effect on the star-forming properties of the galaxies has been largely elucidated and the general consensus is that this process first compresses the gas available in galaxy disks, boosting the star formation for a limited amount of time, and then removes the remaining gas, leading to quenching. Much less is known about the effect and preponderance of RPS at higher redshifts, due to the lack of statistical samples. Exploiting VLT/MUSE observations of galaxies at $0.2<z<0.55$ and a published catalog of ram-pressure-stripped galaxies, we compare the global star formation rate–mass (SFR-- relation of 29 cluster galaxies undergoing RPS to that of 26 undisturbed field and cluster galaxies that constitute our control sample. Stripping galaxies occupy the upper envelope of the SFR– relation of the control sample, showing a systematic enhancement of SFR at any given mass. The boost is $>3 when considering the SFR occurring in both the tail and the disk of the galaxies. The enhancement is also seen on local scales: Considering spatially resolved data, ram-pressure stripped galaxies have large values overall, especially for RPS seems to leave the same imprint on the SFR-- and relations both in the local Universe and at $z
Context . The population of galaxies in the local Universe is bi-modal in terms of the specific star formation rate. This fact has led to a broad distinction between star-forming galaxies (typically cold-gas-rich and late-type) and quenched galaxies (typically cold-gas-poor and early-type). The ratio between quenched and star-forming galaxies is much higher in clusters than the field, and pinpointing which are the physical processes driving this excess quenching in clusters is an open question.
Aims . We used the nearby Coma Cluster as a laboratory to probe the impact of ram pressure on star formation as well as to constrain the characteristic timescales and velocities for the stripping of the non-thermal interstellar medium.
Methods . We used high-resolution (6.5" ≈ 3 kpc), multi-frequency (144 MHz – 1.5 GHz) radio continuum imaging of the Coma Cluster to resolve the low-frequency radio spectrum across the discs and tails of 25 ram-pressure-stripped galaxies. With resolved spectral index maps across these galaxy discs, we constrained the impact of ram pressure perturbations on galaxy star formation. We measured multi-frequency flux-density profiles along each of the ram-pressure-stripped tails in our sample. We then fitted the resulting radio continuum spectra with a simple synchrotron ageing model.
Results . We show that ram-pressure-stripped tails in Coma have steep spectral indices (−2 ≲ α ≲ −1). The discs of galaxies undergoing ram pressure stripping have integrated spectral indices within the expected range for shock acceleration from supernovae (−0.8 ≲ α ≲ −0.5), though there is a tail towards flatter values. In a resolved sense, there are gradients in the spectral index across the discs of ram-pressure-stripped galaxies in Coma. These gradients are aligned with the direction of the observed radio tails, with the flattest spectral indices being found on the ‘leading half’. From best-fit break frequencies, we estimate the projected plasma velocities along the tail to be of the order of hundreds of kilometres per second, with the precise magnitude depending on the assumed magnetic field strength.
Jellyfish galaxies are starburst galaxies with ram-pressure-stripped tails and blue star-forming knots. These galaxies show a snapshot of star formation enhancement triggered by ram pressure stripping (RPS), being important targets for studying the RPS-induced star formation in gas-rich galaxies. Here we investigate the star formation activity of five jellyfish galaxies in massive clusters, using Gemini GMOS/IFU observations. From the H α -derived star formation rates (SFRs), we find that our sample shows higher SFR excess to the star formation main sequence than the jellyfish galaxies in low-mass clusters. From the compiled sample of jellyfish galaxies in low-mass to high-mass host clusters, we suggest that the star formation activity of jellyfish galaxies has positive correlations with host cluster mass and degree of RPS. These relationships imply that higher ram pressure environments tend to trigger stronger starbursts in jellyfish galaxies in the early stage of RPS.
We analyse cold-gas distributions in Virgo cluster galaxies using resolved observations of CO(2-1), which traces molecular hydrogen (H 2 ), and H I from the Virgo Environment Traced In CO (VERTICO) and VLA Imaging of Virgo in Atomic Gas (VIVA) surveys. From a theoretical perspective, it is expected that environmental processes in clusters will have a stronger influence on diffuse atomic gas compared to the relatively dense molecular gas component, and that these environmental perturbations can compress the cold interstellar medium in cluster galaxies, leading to elevated star formation. In this work we observationally test these predictions for star-forming satellite galaxies within the Virgo cluster. We divided our Virgo galaxy sample into H I -normal, H I -tailed, and H I -truncated classes and show, unsurprisingly, that the H I -tailed galaxies have the largest quantitative H I asymmetries. We also compared Virgo galaxies to a control sample of non-cluster galaxies and find that the former, on average, have H I asymmetries that are 40 ± 10% larger than the latter. There is less separation between control, H I -normal, H I -tailed, and H I -truncated galaxies in terms of H 2 asymmetries, and on average, Virgo galaxies have H 2 asymmetries that are only marginally (20 ± 10%) larger than the control sample. We find a weak correlation between H I and H 2 asymmetries over our entire sample, but a stronger correlation for the galaxies that are strongly impacted by environmental perturbations. Finally, we divided the discs of the H I -tailed Virgo galaxies into a leading half and trailing half according to the observed tail direction. We find evidence for excess molecular gas mass on the leading halves of the disc. This excess molecular gas is accompanied by an excess in the star formation rate such that the depletion time is, on average, unchanged.
