FIG 1 - uploaded by John J. Feldmeier
Content may be subject to copyright.
-Hα+[NII] image of M86 region superposed on a color SDSS gri image. The Hα image is stretched to highlight the faint emission. The "low-velocity" (<500 km/s) Hα+[NII] emission is colored red, and the "high-velocity" (>2000 km/s) Hα+[NII] emission is colored green. The low-velocity emission is attributed to gas stripped from NGC 4438 in a collision with M86 and subsequently heated. High-velocity emission is observed near NGC 4388 in the lower right, although it does not extend all the way to M86, so it is unclear whether it is related.

-Hα+[NII] image of M86 region superposed on a color SDSS gri image. The Hα image is stretched to highlight the faint emission. The "low-velocity" (<500 km/s) Hα+[NII] emission is colored red, and the "high-velocity" (>2000 km/s) Hα+[NII] emission is colored green. The low-velocity emission is attributed to gas stripped from NGC 4438 in a collision with M86 and subsequently heated. High-velocity emission is observed near NGC 4388 in the lower right, although it does not extend all the way to M86, so it is unclear whether it is related.

Source publication
Article
Full-text available
Deep wide-field H$\alpha$+[NII] imaging around the Virgo cluster giant elliptical galaxy M86 reveals a highly complex and disturbed ISM/ICM. The most striking feature is a set of H$\alpha$ filaments which clearly connect M86 with the nearby disturbed spiral NGC 4438 (23$'$=120 kpc projected away), providing strong evidence for a previously unrecogn...

Context in source publication

Context 1
... were pro- cessed and mosaiced together in a standard way, except for ad- ditional flat fielding corrections using masked image frames, and a pupil correction for the Hα images. The Hα image superposed on an SDSS gri image (Adelman-McCarthy et al 2007) is shown in Figure 1, the R-band image is shown in We obtained spectroscopy at 24 selected positions near M86 with the SparsePak integral field unit (IFU) on the WIYN telescope. SparsePak ( Bershady et al. 2004) is a 90-fiber array which loosely covers an 80 ′′ ×80 ′′ field of view, with 5" diameter fibers. ...

Similar publications

Article
Full-text available
A strong X-ray emission is one of the defining signatures of nuclear activity in galaxies. According to the Unified Model for Active Galactic Nuclei (AGN), both the X-ray radiation and the prominent broad emission lines, characterizing the optical and UV spectra of Type 1 AGNs, are originated in the innermost regions of the sources, close to the Su...
Article
Full-text available
Giant radio galaxies are arguably the least understood of jetted active galactic nuclei (AGN). We propose that radio galaxies are the product of large mergers that do not involve radio galaxies or radio quasars, such as in merging spiral galaxies, while giant radio galaxies emerge from a merger involving a parent that in the not-too-distant past ha...
Preprint
Full-text available
The morphological study is crucial to investigate the connections between active galactic nuclei (AGN) activities and the evolution of galaxies. Substantial studies have found that radiative-mode AGNs primarily reside in disk galaxies, questioning the merger-driven mechanism of AGN activities. In this study, through S{\'e}rsic profile fitting and n...
Article
Full-text available
Star-forming galaxies at high redshift show anomalous values of infrared excess, which can be described only by extremizing the existing relations between the shape of their ultraviolet continuum emission and their infrared-to-ultraviolet luminosity ratio, or by constructing ad-hoc models of star formation and dust distribution. We present an alter...
Article
Full-text available
How efficiently star formation proceeds in galaxies is still an open question. Recent studies suggest that AGN can regulate the gas accretion and thus slow down star formation (negative feedback). However, evidence of AGN positive feedback has also been observed in a few radio galaxies (eg. Centaurus A). Here we present CO observations of 3C 285 an...

Citations

... These features are tidal tails formed after the gravitational interaction of the galaxy with M86 and NGC 4435 (e.g. Combes et al. 1988;Boselli et al. 2005;Kenney et al. 2008). Although the gas can be partly removed by ram pressure (Vollmer et al. 2009), the dominant perturbing mechanism is gravitational since able to act on the stellar component. ...
Article
Full-text available
Galaxies living in rich environments are suffering different perturbations able to drastically affect their evolution. Among these, ram pressure stripping, i.e. the pressure exerted by the hot and dense intracluster medium (ICM) on galaxies moving at high velocity within the cluster gravitational potential well, is a key process able to remove their interstellar medium (ISM) and quench their activity of star formation. This review is aimed at describing this physical mechanism in different environments, from rich clusters of galaxies to loose and compact groups. We summarise the effects of this perturbing process on the baryonic components of galaxies, from the different gas phases (cold atomic and molecular, ionised, hot) to magnetic fields and cosmic rays, and describe their induced effects on the different stellar populations, with a particular attention to its role in the quenching episode generally observed in high-density environments. We also discuss on the possible fate of the stripped material once removed from the perturbed galaxies and mixed with the ICM, and we try to estimate its contribution to the pollution of the surrounding environment. Finally, combining the results of local and high-redshift observations with the prediction of tuned models and simulations, we try to quantify the importance of this process on the evolution of galaxies of different mass, from dwarfs to giants, in various environments and at different epochs.
... Observational measurements and upper limits are shown as discrete symbols. Bright Hα features include the M82 Cap (Lehnert et al. 1999), the Virgo filaments (Kenney et al. 2008), edge-on galaxies (Christlein et al. 2010), NGC 7793 (Dicaire et al. 2008), UGC 7321 (Adams et al. 2011), NGC 247 (Hlavacek-Larrondo et al. 2011, the outer disk of M31 (Madsen et al. 2001), the Leo Ring (Donahue et al. 1995), and the Virgo HI cloud (Weymann et al. 2001). The dashed and solid light grey lines around 100 mR represent Hα emission observations and surface brightness predictions for the Magellanic stream/bridge (Bland-Hawthorn et al. 2007;Barger et al. 2013). ...
Preprint
Full-text available
The Circumgalactic H$\alpha$ Spectrograph (CH$\alpha$S) is a ground-based optical integral field spectrograph designed to detect ultra-faint extended emission from diffuse ionized gas in the nearby universe. CH$\alpha$S is particularly well suited for making a direct detection of tenuous H$\alpha$ emission from the circumgalactic medium (CGM) surrounding low-redshift galaxies. It efficiently maps large regions of the CGM in a single exposure, targeting nearby galaxies (d $< 35 $ Mpc) where the CGM is expected to fill the field of view. We are commissioning CH$\alpha$S as a facility instrument at MDM Observatory. CH$\alpha$S is deployed in the focal plane of the Hiltner 2.4-meter telescope, utilizing nearly all of the telescope's unvignetted focal plane (10 arcmin) to conduct wide-field spectroscopic imaging. The catadioptric design provides excellent wide-field imaging performance. CH$\alpha$S is a pupil-imaging spectrograph employing a microlens array to divide the field of view into $> 60,000$ spectra. CH$\alpha$S achieves an angular resolution of $[1.3 - 2.8]$ arcseconds and a resolving power of R$ = [10,000 - 20,000]$. Accordingly, the spectrograph can resolve structure on the scale of $1-5$ kpc (at 10 Mpc) and measure velocities down to 15-30 km/s. CH$\alpha$S intentionally operates over a narrow (30 Angstrom) bandpass; however, it is configured to adjust the central wavelength and target a broad range of optical emission lines individually. A high diffraction efficiency VPH grating ensures high throughput across configurations. CH$\alpha$S maintains a high grasp and moderate spectral resolution, providing an ideal combination for mapping discrete, ultra-low surface brightness emission on the order of a few milli-Raleigh.
... We also note that BC4 is in the vicinity of SECCO 1 and Sand et al. (2017) suggested the same subgroup of Virgo (containing NGC 4402 and NGC 4438) as the potential source of the gas in that object. The extension of NGC 4402 to the NW (Crowl et al. 2005;Chung et al. 2009) and the highly disturbed Hα emission (Kenney et al. 2008;Sand et al. 2017) in the vicinity of both galaxies makes them both plausible candidates for the origin of SECCO 1. However, this does not preclude them also being candidates for BC4. ...
Article
Full-text available
We discuss five blue stellar systems in the direction of the Virgo cluster, analogous to the enigmatic object SECCO 1 (AGC 226067). These objects were identified based on their optical and UV morphology and followed up with H i observations with the Very Large Array (and Green Bank Telescope), Multi Unit Spectroscopic Explorer (on the Very Large Telescope) optical spectroscopy, and Hubble Space Telescope imaging. These new data indicate that one system is a distant group of galaxies. The remaining four are extremely low mass ( M * ∼ 10 ⁵ M ⊙ ), are dominated by young blue stars, have highly irregular and clumpy morphologies, are only a few kiloparsecs across, yet host an abundance of metal-rich, 12 + log ( O / H ) > 8.2 , H ii regions. These high metallicities indicate that these stellar systems formed from gas stripped from much more massive galaxies. Despite the young age of their stellar populations, only one system is detected in H i , while the remaining three have minimal (if any) gas reservoirs. Furthermore, two systems are surprisingly isolated and have no plausible parent galaxy within ∼30′ (∼140 kpc). Although tidal stripping cannot be conclusively excluded as the formation mechanism of these objects, ram pressure stripping more naturally explains their properties, in particular their isolation, owing to the higher velocities, relative to the parent system, that can be achieved. Therefore, we posit that most of these systems formed from ram-pressure-stripped gas removed from new infalling cluster members and survived in the intracluster medium long enough to become separated from their parent galaxies by hundreds of kiloparsecs and that they thus represent a new type of stellar system.
... We also note that BC4 is in the vicinity of SECCO 1 and Sand et al. (2017) suggested the same sub-group of Virgo (containing NGC 4402 and NGC 4438) as the potential source of the gas in that object. The extension of NGC 4402 to the NW (Crowl et al. 2005;Chung et al. 2009) and the highly disturbed Hα emission (Kenney et al. 2008;Sand et al. 2017) in the vicinity of both galaxies makes them both plausible candidates for the origin of SECCO 1. However, this does not preclude them also being candidates for BC4. ...
Preprint
Full-text available
We discuss five blue stellar systems in the direction of the Virgo cluster, analogous to the enigmatic object SECCO 1 (AGC 226067). These objects were identified based on their optical and UV morphology and followed up with HI observations with the VLA (and GBT), MUSE/VLT optical spectroscopy, and HST imaging. These new data indicate that one system is a distant group of galaxies. The remaining four are extremely low mass ($M_\ast \sim 10^5 \; \mathrm{M_\odot}$), are dominated by young, blue stars, have highly irregular and clumpy morphologies, are only a few kpc across, yet host an abundance of metal-rich, $12 + \log (\mathrm{O/H}) > 8.2$, HII regions. These high metallicities indicate that these stellar systems formed from gas stripped from much more massive galaxies. Despite the young age of their stellar populations, only one system is detected in HI, while the remaining three have minimal (if any) gas reservoirs. Furthermore, two systems are surprisingly isolated and have no plausible parent galaxy within $\sim$30' ($\sim$140 kpc). Although tidal stripping cannot be conclusively excluded as the formation mechanism of these objects, ram pressure stripping more naturally explains their properties, in particular their isolation, owing to the higher velocities, relative to the parent system, that can be achieved. Therefore, we posit that most of these systems formed from ram pressure stripped gas removed from new infalling cluster members, and survived in the intracluster medium long enough to become separated from their parent galaxies by hundreds of kiloparsecs, and that they thus represent a new type of stellar system.
... It is a dynamically young system that shows many substructures of member galaxies both spatially and kinematically (Binggeli et al. 1985(Binggeli et al. , 1987. In particular, the core region of the Virgo shows diffuse stellar features (Mihos et al. 2005(Mihos et al. , 2017 and extended structures of ionized gas filaments (Kenney et al. 2008;Boselli et al. 2018) and HI gas (Yoshida et al. 2002;Oosterloo & van Gorkom 2005) around galaxies, indicative of strong galaxy interactions. The most massive galaxy at the center of the Virgo, M87, has a weak cD envelope, and kinematic studies of GCs and PNe have been done to understand the connection between its faint stellar halo and the intracluster light (Longobardi et al. 2015a;Ko et al. 2017;Longobardi et al. 2018a,b). ...
Preprint
Full-text available
We present a study of the stellar populations of globular clusters (GCs) in the Virgo Cluster core with a homogeneous spectroscopic catalog of 692 GCs within a major axis distance $R_{\rm maj} = $ 840 kpc from M87. We investigate radial and azimuthal variations in the mean age, total metallicity, [Fe/H], and $\alpha$-element abundance, of blue (metal-poor) and red (metal-rich) GCs using their co-added spectra. We find that the blue GCs have a steep radial gradient in [Z/H] within $R_{\rm maj} =$ 165 kpc, with roughly equal contributions from [Fe/H] and [$\alpha$/Fe], and flat gradients beyond. By contrast, the red GCs show a much shallower gradient in [Z/H], which is entirely driven by [Fe/H]. We use GC-tagged Illustris simulations to demonstrate an accretion scenario where more massive satellites (with more metal- and $\alpha$-rich GCs) sink further into the central galaxy than less massive ones, and where the gradient flattening occurs because of the low GC occupation fraction of low-mass dwarfs disrupted at larger distances. The dense environment around M87 may also cause the steep [$\alpha$/Fe] gradient of the blue GCs, mirroring what is seen in the dwarf galaxy population. The progenitors of red GCs have a narrower mass range than those of blue GCs, which makes their gradients shallower. We also explore spatial inhomogeneity in GC abundances, finding that the red GCs to the northwest of M87 are slightly more metal-rich. Future observations of GC stellar population gradients will be useful diagnostics of halo merger histories.
... SOFIA FIFI-LS observations were obtained for the nearest 6 out of the 12 proposed galaxies. The six galaxies included here should be regarded as an ex- Note-(1) : Galaxy name ; (2) : velocity from NED ; (3) : distance from Tonry et al. (2001); (4) : linear size conversion; (5) : Galaxy Type; Type T parameter in brackets from hyperleda a (6) : absolute K band magnitude MK (2MASS keyword k m ext) from Cappellari et al. (2011); (7) : effective radius Re from Cappellari et al. (2011);(8,9,10) : ellipticity, specific stellar angular momentum, Fast or Slow rotator (Slow if 0.31 √ e/λRe > 1) at Re; (11,12) : Hα+ [NII] fluxes and references (1 : Gavazzi et al. (2018); 2 : Trinchieri & di Serego Alighieri (1991); 3 : Kenney et al. (2008); 4 : Macchetto et al. (1996); 5 : Ho et al. (1997); 6 : Boselli et al. (2021)) (13) : gas mass estimated using a gas-to-dust ratio of 100 and the dust masses calculated by Amblard et al. (2014) using Spitzer and Herschel fluxes of these galaxies (Temi et al. 2009;Amblard et al. 2014); a :added to the sample to present new ALMA CO(3-2) data. a http://leda.univ-lyon1.fr/ ...
... HST dust image shows some residual emission at its center and a plume along the radial direction extending ∼ 4 . Morphologically complex warm ionized gas has been detected through Hα emission (Kenney et al. 2008). linking NGC 4406 to the spiral galaxy NGC 4438, that lies 23 (120 kpc) away. ...
... Sabater et al. 2013). Indeed lines of support include: i) recent observations of Hα emission in NGC 4406 (Kenney et al. 2008), some of which is colocated in the region of its X-ray plume, suggest a collision with NGC 4438 as its origin; ii) NGC 4261 has a well defined disk of dust, 240 pc in diameter, that is aligned with its radio axis and perpendicular to the stellar component of the galaxy; iii) in NGC 4374 the dust lane major axis is strongly misaligned with the major axis of the stars and the kinematic of molecular gas is inconsistent with a stellar mass loss origin; iv) the giant elliptical NGC 4552 which is falling into the Virgo cluster, has central X-ray emission features (Machacek et al. 2006a) characteristic of a supersonic ram-pressure stripping of the gas, produced by its motion in the Virgo ICM. Overall, albeit suggestive, these remain qualitative features that require to be further tested with future targeted and deeper observations. ...
Article
Full-text available
We investigate the cold and warm gas content, kinematics, and spatial distribution of six local massive elliptical galaxies to probe the origin of the multiphase gas in their atmospheres. We report new observations, including Stratospheric Observatory for Infrared Astronomy [C ii ], Atacama Large Millimeter/submillimeter Array CO, Multi Unit Spectroscopic Explorer (MUSE) H α +[N ii ], and Very Large Array (VLA) radio observations. These are complemented by a large suite of multiwavelength archival data sets, including thermodynamical properties of the hot gas and radio jets, which are leveraged to investigate the role of active galactic nucleus (AGN) feeding/feedback in regulating the multiphase gas content. Our galactic sample shows a significant diversity in cool gas content, spanning filamentary and rotating structures. In our noncentral galaxies, the distribution of such gas is often concentrated, at variance with the more extended features observed in central galaxies. Misalignment between the multiphase gas and stars suggest that stellar mass loss is not the primary driver. A fraction of the cool gas might be acquired via galaxy interactions, but we do not find quantitative evidence of mergers in most of our systems. Instead, key evidence supports the origin via condensation out of the diffuse halo. Comparing with chaotic cold accretion (CCA) simulations, we find that our cool gas-free galaxies are likely in the overheated phase of the self-regulated AGN cycle, while for our galaxies with cool gas, the k-plot and AGN power correlation corroborate the phase of CCA feeding in which the condensation rain is triggering more vigorous AGN heating. The related C-ratio further shows that central/noncentral galaxies are expected to generate an extended/inner rain, consistent with our sample.
... For a star-forming galaxy, the cold gas that serves as the fuel for star formation can be removed through ram pressure stripping and eventually "quench" the galaxy. There are ample observations of lopsided, clearly ram pressure stripped tails in HI [65,21,1], Hα [118,119,147,148,149,66], X-rays [136,42,111], and radio [61] among cluster galaxies. ...
Preprint
As the formation of cosmic structure continues to proceed, we observe one of the latest stages of this process in mergers of clusters of galaxies with other clusters, groups, and galaxies. The X-ray emitting hot plasma of these systems can be dramatically affected by these mergers, producing cold and shock fronts, gas sloshing, bulk motions, and turbulence. Combined with numerical simulations, observations of these features can be used to constrain the plasma physics of the hot gas as well as its interaction with high-energy cosmic rays. In this chapter, we review these topics and point forward to what the capabilities of future observatories will reveal.
... SOFIA FIFI-LS observations were obtained for the nearest 6 out of the 12 proposed galaxies. The six galaxies included here should be regarded as an ex- Note-(1) : Galaxy name ; (2) : velocity from NED ; (3) : distance from Tonry et al. (2001); (4) : linear size conversion; (5) : Galaxy Type; Type T parameter in brackets from hyperleda a (6) : absolute K band magnitude MK (2MASS keyword k m ext) from Cappellari et al. (2011); (7) : effective radius Re from Cappellari et al. (2011);(8,9,10) : ellipticity, specific stellar angular momentum, Fast or Slow rotator (Slow if 0.31 √ e/λRe > 1) at Re; (11,12) : Hα+ [NII] fluxes and references (1 : Gavazzi et al. (2018); 2 : Trinchieri & di Serego Alighieri (1991); 3 : Kenney et al. (2008); 4 : Macchetto et al. (1996); 5 : Ho et al. (1997); 6 : Boselli et al. (2021)) (13) : gas mass estimated using a gas-to-dust ratio of 100 and the dust masses calculated by Amblard et al. (2014) using Spitzer and Herschel fluxes of these galaxies (Temi et al. 2009;Amblard et al. 2014); a :added to the sample to present new ALMA CO(3-2) data. a http://leda.univ-lyon1.fr/ ...
... HST dust image shows some residual emission at its center and a plume along the radial direction extending ∼ 4 . Morphologically complex warm ionized gas has been detected through Hα emission (Kenney et al. 2008). linking NGC 4406 to the spiral galaxy NGC 4438, that lies 23 (120 kpc) away. ...
... Sabater et al. 2013). Indeed lines of support include: i) recent observations of Hα emission in NGC 4406 (Kenney et al. 2008), some of which is colocated in the region of its X-ray plume, suggest a collision with NGC 4438 as its origin; ii) NGC 4261 has a well defined disk of dust, 240 pc in diameter, that is aligned with its radio axis and perpendicular to the stellar component of the galaxy; iii) in NGC 4374 the dust lane major axis is strongly misaligned with the major axis of the stars and the kinematic of molecular gas is inconsistent with a stellar mass loss origin; iv) the giant elliptical NGC 4552 which is falling into the Virgo cluster, has central X-ray emission features (Machacek et al. 2006a) characteristic of a supersonic ram-pressure stripping of the gas, produced by its motion in the Virgo ICM. Overall, albeit suggestive, these remain qualitative features that require to be further tested with future targeted and deeper observations. ...
Preprint
Full-text available
We investigate the cold and warm gas content, kinematics, and spatial distribution of six local massive elliptical galaxies to probe the origin of the multiphase gas in their atmospheres. We report new observations, including SOFIA [CII], ALMA CO, MUSE H$\alpha$+[NII] and VLA radio observations. These are complemented by a large suite of multiwavelength archival datasets, including thermodynamical properties of the hot gas and radio jets, which are leveraged to investigate the role of AGN feeding/feedback in regulating the multiphase gas content. Our galaxy sample shows a significant diversity in cool gas content, spanning filamentary and rotating structures. In our non-central galaxies, the distribution of such gas is often concentrated, at variance with the more extended features observed in central galaxies. Misalignment between the multiphase gas and stars suggest that stellar mass loss is not the primary driver. A fraction of the cool gas might be acquired via galaxy interactions, but we do not find quantitative evidence of mergers in most of our systems. Instead, key evidence supports the origin via condensation out of the diffuse halo. Comparing with Chaotic Cold Accretion (CCA) simulations, we find that our cool gas-free galaxies are likely in the overheated phase of the self-regulated AGN cycle, while for our galaxies with cool gas the k-plot and AGN power correlation corroborate the phase of CCA feeding in which the condensation rain is triggering more vigorous AGN heating. The related C-ratio further shows that central/non-central galaxies are expected to generate an extended/inner rain, consistent with our sample.
... The stripping tails of cluster late-type galaxies have been observed from radio, mm, IR, and optical to X-ray (e.g. Gavazzi et al. 2001;Yoshida et al. 2002;Yagi et al. 2007;Chung et al. 2007;Kenney et al. 2008;Sun et al. 2010;Sivanandam et al. 2010;Merluzzi et al. 2013;Jáchym et al. 2014;Boselli et al. 2016;Chen et al. 2020). In contrast to the early general wisdom that the stripped cold gas will simply mix with the hot ICM and be heated, now it is known that some fraction of the stripped ISM can collapse and form stars in the galactic halo and the intracluster space, especially in high-ICM-pressure environments (e.g. ...
Article
Full-text available
Recent studies have highlighted the potential significance of intracluster medium (ICM) clumping and its important implications for cluster cosmology and baryon physics. Many of the ICM clumps can originate from infalling galaxies, as stripped interstellar medium (ISM) mixing into the hot ICM. However, a direct connection between ICM clumping and stripped ISM has not been unambiguously established before. Here, we present the discovery of the first and still the only known isolated cloud (or orphan cloud [OC]) detected in both X-rays and H α in the nearby cluster A1367. With an effective radius of 30 kpc, this cloud has an average X-ray temperature of 1.6 keV, a bolometric X-ray luminosity of ∼3.1 × 1041 erg s−1, and a hot gas mass of ∼1010 M⊙. From the Multi-Unit Spectroscopic Explorer (MUSE) data, the OC shows an interesting velocity gradient nearly along the east-west direction with a low level of velocity dispersion of ∼80 km s−1, which may suggest a low level of the ICM turbulence. The emission line diagnostics suggest little star formation in the main H α cloud and a low-ionization (nuclear) emission-line regions like spectrum, but the excitation mechanisms remain unclear. This example shows that stripped ISM, even long after the initial removal from the galaxy, can still induce ICM inhomogeneities. We suggest that the magnetic field can stabilize the OC by suppressing hydrodynamic instabilities and thermal conduction. This example also suggests that at least some ICM clumps are multiphase in nature and implies that the ICM clumps can also be traced in H α. Thus, future deep and wide-field H α surveys can be used to probe the ICM clumping and turbulence.
... The stripping tails of cluster late-type galaxies have been observed from radio, mm, IR, and optical to X-ray (e.g. Gavazzi & Jaffe 1987;Gavazzi et al. 2001;Yoshida et al. 2002Yoshida et al. , 2004Oosterloo & van Gorkom 2005;Sun et al. 2007b;Yagi et al. 2007;Chung et al. 2007;Yoshida et al. 2008;Kenney et al. 2008;Sun et al. 2010;Yagi et al. 2010;Smith et al. 2010;Hester et al. 2010;Sivanandam et al. 2010;Fossati et al. 2012;Merluzzi et al. 2013;Jáchym et al. 2014;Kenney et al. 2014;Boselli et al. 2016;Poggianti et al. 2017;Gavazzi et al. 2018;Chen et al. 2020). In contrast to the early general wisdom that the stripped cold gas will simply mix with the hot ICM and be heated, now it is known that some fraction of the stripped ISM can collapse and form stars in the galactic halo and the intracluster space, especially in high-ICM-pressure environments (e.g. ...
Preprint
Full-text available
Recent studies have highlighted the potential significance of intracluster medium (ICM) clumping and its important implications for cluster cosmology and baryon physics. Many of the ICM clumps can originate from infalling galaxies, as stripped interstellar medium (ISM) mixing into the hot ICM. However, a direct connection between ICM clumping and stripped ISM has not been unambiguously established before. Here we present the discovery of the first and still the only known isolated cloud (or orphan cloud, OC) detected in both X-rays and H$\alpha$ in the nearby cluster Abell 1367. With an effective radius of 30 kpc, this cloud has an average X-ray temperature of 1.6 keV, a bolometric X-ray luminosity of $\sim 3.1\times 10^{41}$ erg s$^{-1}$ and a hot gas mass of $\sim 10^{10}\ {\rm M}_\odot$. From the MUSE data, the OC shows an interesting velocity gradient nearly along the east-west direction with a low level of velocity dispersion of $\sim 80$ km/s, which may suggest a low level of the ICM turbulence. The emission line diagnostics suggest little star formation in the main H$\alpha$ cloud and a LI(N)ER-like spectrum, but the excitation mechanism remain unclear. This example shows that the stripped ISM, even long time after the initial removal from the galaxy, can still induce the ICM inhomogeneities. We suggest that magnetic field can stabilize the OC by suppressing hydrodynamic instabilities and thermal conduction. This example also suggests that at least some ICM clumps are multi-phase in nature and implies that the ICM clumps can also be traced in H$\alpha$. Thus, future deep and wide-field H$\alpha$ survey can be used to probe the ICM clumping and turbulence.