More Like this

1. ESO 137-002: a large spiral undergoing edge-on ram-pressure stripping with little star formation in the tail

   https://doi.org/10.1093/mnras/stab3280  

   Laudari, Sunil; Jáchym, Pavel; Sun, Ming; Waldron, Will; Chatzikos, Marios; Kenney, Jeffrey; Luo, Rongxin; Nulsen, Paul; Sarazin, Craig; Combes, Françoise; et al (November 2021, Monthly Notices of the Royal Astronomical Society)

   ABSTRACT Ram pressure stripping (RPS) is an important mechanism for galaxy evolution. In this work, we present results from HST and APEX observations of one RPS galaxy, ESO 137-002 in the closest rich cluster Abell 3627. The galaxy is known to host prominent X-ray and H α tails. The HST data reveal significant features indicative of RPS in the galaxy, including asymmetric distribution of dust in the galaxy, dust filaments, and dust clouds in ablation generally aligned with the direction of ram pressure, and young star clusters immediately upstream of the residual dust clouds that suggest star formation (SF) triggered by RPS. The distribution of the molecular gas is asymmetric in the galaxy, with no CO upstream and abundant CO downstream and in the inner tail region. A total amount of ∼5.5 × 109 M⊙ of molecular gas is detected in the galaxy and its tail. On the other hand, we do not detect any active SF in the X-ray and H α tails of ESO 137-002 with the HST data and place a limit on the SF efficiency in the tail. Hence, if selected by SF behind the galaxy in the optical or UV (e.g. surveys like GASP or using the Galex data), ESO 137-002 will not be considered a ‘jellyfish’ galaxy. Thus, galaxies like ESO 137-002 are important for our comprehensive understanding of RPS galaxies and the evolution of the stripped material. ESO 137-002 also presents a great example of an edge-on galaxy experiencing a nearly edge-on RPS wind. 

   more » « less
2. ALMA-JELLY. I. High Resolution CO(2–1) Observations of Ongoing Ram Pressure Stripping in NGC 4858 Reveal Asymmetrical Gas Tail Formation and Fallback

   https://doi.org/10.3847/1538-4357/adde47  

   Souchereau, Harrison J; Kenney, Jeffrey_D P; Jáchym, Pavel; Sun, Ming; Cramer, William J; Yagi, Masafumi; Boselli, Alessandro; Brinks, Elias; Combes, Francoise; Cortese, Luca; et al (July 2025, The Astrophysical Journal)

   Abstract We present new CO(2–1) observations (resolution ∼1″ = 460 pc) of the Coma cluster jellyfish galaxy NGC 4858 obtained from the ALMA-JELLY large program. Analyzing this data alongside complimentary Subaru Hαand Hubble Space Telescope (F600LP / F350LP) observations, we find numerous structural and kinematic features indicative of the effects from strong, inclined ram pressure, including an asymmetric inner gas tail. We estimate a highly inclined disk-wind angle of ${\varphi }_{\text{DW}}=75_{-27}^{+10}$. By subtracting a simple circular velocity model, we find (1): gas clumps that are being accelerated by ram pressure, and (2): signatures of gas clumps that had been previously pushed out of the disk but are now falling inward. We also discuss head-tail morphologies in star complexes within the stellar disk that appear to be ram pressure stripping (RPS)-influenced. Lastly, we compare this galaxy to state-of-the-art galaxy “wind tunnel” simulations. We find that this galaxy is one of the best nearby examples of strong and inclined ram pressure gas stripping, and of gas that is perturbed by ram pressure but not fully stripped and falls back. We emphasize the importance of torques due to ram pressure in highly inclined interactions, which help drive gas inward on the side rotating against the wind, contributing to the formation of asymmetric inner RPS tails. 

   more » « less
3. ESO 137–001: A jellyfish galaxy model

   https://doi.org/10.1051/0004-6361/202450435  

   Vollmer, B; Sun, M; Jachym, P; Fossati, M; Boselli, A (December 2024, Astronomy & Astrophysics)

   Ram-pressure stripping of the spiral galaxy ESO 137−001 within the highly dynamical intracluster medium (ICM) of the Norma cluster lead to spectacular extraplanar CO, optical, Hα, UV, and X-ray emission. The Hαand X-ray tails extend up to 80 kpc from the galactic disk. We present dynamical simulations of the ram-pressure stripping event, and investigate the physics of the stripped gas and its ability to form stars. We also use these simulations to predict H Imaps and to constrain the orbit of ESO 137−001 within the Norma cluster. Special care was taken for the stripping of the diffuse gas. In a new approach, we analytically estimate the mixing between the intracluster and interstellar media. Different temporal ram-pressure profiles and the ICM-ISM mixing rate were tested. Three preferred models show most of the observed multiwavelength characteristics of ESO 137−001. Our highest-ranked model best reproduces the CO emission distribution, velocity for distances of ≲20 kpc from the galactic disk, and the available near-ultraviolet (NUV) observations. The second and third preferred models best reproduce the available X-ray and Hαobservations of the gas tail, including the Hαvelocity field. The angle between the direction of the galaxy’s motion and the plane of the galactic disk is between 60° and 75°. Ram-pressure stripping thus occurs more face-on. The existence of a two-tailed structure is a common feature in our models, and is due to the combined action of ram pressure and rotation together with the projection of the galaxy on the sky. Our modeling of the Hαemission caused by ionization through thermal conduction is consistent with observations. We predict the H Iemission distributions for the different models. Based on the 3D velocity vector derived from our dynamical model, we derive a galaxy orbit, which is close to unbound. We argue that ram pressure is enhanced by a factor of ∼2.5 compared to that expected for an orbit in an unperturbed spherical ICM. This increase can be obtained in two ways: an increase in the ICM density or a moving ICM opposite to the motion of the galaxy within the cluster. In a strongly perturbed galaxy cluster, such as the Norma cluster, with an off-center ICM distribution, the two possibilities are probable and plausible. 

   more » « less
4. Turbulence in the tail of a jellyfish galaxy

   https://doi.org/10.1093/mnras/stad874  

   Li, Yuan; Luo, Rongxin; Fossati, Matteo; Sun, Ming; Jáchym, Pavel (March 2023, Monthly Notices of the Royal Astronomical Society)

   ABSTRACT When galaxies move through the intracluster medium (ICM) inside galaxy clusters, the ram pressure of the ICM can strip the gas from galaxies. The stripped gas forms tails on the trailing side. These galaxies are hence dubbed ‘jellyfish galaxies’. ESO 137-001 is a quintessential jellyfish galaxy located in the nearest rich cluster, the Norma cluster. Its spectacular multiphase tail has complex morphology and kinematics both from the imprinted galaxy’s interstellar medium (ISM) and as a result of the interactions between the stripped gas and the surrounding hot plasma, mediated by radiative cooling and magnetic fields. We study the kinematics of the multiphase tail using high-resolution observations of the ionized and the molecular gas in the entire structure. We calculate the velocity structure functions in moving frames along the tail and find that turbulence driven by Kelvin–Helmholtz (KH) instability quickly overwhelms the original ISM turbulence and saturates at ∼30 kpc. There is also a hint that the far end of the tail has possibly started to inherit pre-existing large-scale ICM turbulence likely caused by structure formation. Turbulence measured by the molecular gas is generally consistent with that measured by the ionized gas in the tail but has a slightly lower amplitude. Most of the measured turbulence is below the mean free path of the hot ICM (∼11 kpc). Using warm/cool gas as a tracer of the hot ICM, we find that the isotropic viscosity of the hot plasma must be suppressed below 0.01 per cent Spitzer level. 

   more » « less
5. MeerKAT HI imaging of the jellyfish galaxy ESO 137-001

   https://doi.org/10.1051/0004-6361/202451050  

   Ramatsoku, M; Serra, P; Sun, M; Smirnov, O M; Makhathini, S (February 2025, Astronomy & Astrophysics)

   We present MeerKAT H Iobservations of ESO 137-001, a quintessential jellyfish galaxy with long multi-phase tails formed due to the interaction with the intra-cluster medium of its host galaxy cluster, ACO 3627. Our observations reveal the presence of H Iin both the disc and outer regions of the galaxy for the first time, with a total H Imass of (3.5 ± 0.4)×10⁸M_⊙. ESO 137-001 is at an advanced stage of gas stripping; it is extremely H Ideficient and seems to have lost 90% of its initial H Imass; about 2/3 of the surviving H Iis found at larger radius than expected for a normal H Idisc and forms ∼40 kpc tail coincident with the tail detected at other wavelengths. Only ∼10% of the surviving H Iis still found within the stellar disc, consistent with the expectation of an outside-in truncation due to ram pressure. Similarly to other jellyfish galaxies, ESO137-001 has a high star formation rate for the low amount of H Idetected. We measure an H Idepletion time of 0.29 Gyr. However, when taking into account the total gas (H I+ H₂) content, the depletion time is consistent with typical values measured in nearby spiral galaxies. This suggests that ESO 137-001 is at its current stage of ram pressure interaction characterised by an efficient H Istripping, rather than an enhanced conversion of H Ito H₂, which was recently observed in some other jellyfish galaxies. 

   more » « less