1,269 research outputs found
Jellyfish: The origin and distribution of extreme ram-pressure stripping events in massive galaxy clusters
We investigate the observational signatures and physical origin of ram-pressure stripping (RPS) in 63 massive galaxy clusters at z = 0.3â0.7, based on images obtained with the Hubble Space Telescope. Using a training set of a dozen âjellyfishâ galaxies identified earlier in the same imaging data, we define morphological criteria to select 211 additional, less obvious cases of RPS. Spectroscopic follow-up observations of 124 candidates so far confirmed 53 as cluster members. For the brightest and most favourably aligned systems, we visually derive estimates of the projected direction of motion based on the orientation of apparent compression shocks and debris trails. Our findings suggest that the onset of these events occurs primarily at large distances from the cluster core (>400 kpc), and that the trajectories of the affected galaxies feature high-impact parameters. Simple models show that such trajectories are highly improbable for galaxy infall along filaments but common for infall at high velocities, even after observational biases are accounted for, provided the duration of the resulting RPS events is â˛500 Myr. We thus tentatively conclude that extreme RPS events are preferentially triggered by cluster mergers, an interpretation that is supported by the disturbed dynamical state of many of the host clusters. This hypothesis implies that extreme RPS might occur also near the cores of merging poor clusters or even merging groups of galaxies. Finally, we present nine additional âjellyfishâ galaxies at z > 0.3 discovered by us, thereby doubling the number of such systems known at intermediate redshift
Galaxy interactions in IllustrisTNG-100, I: The power and limitations of visual identification
We present a sample of 446 galaxy pairs constructed using the cosmological simulation IllustrisTNG-100 at z = 0, with M_(FoF,dm)=10ššâ10^(13.5) Mâ. We produce ideal mock SDSS g-band images of all pairs to test the reliability of visual classification schema employed to produce samples of interacting galaxies. We visually classify each image as interacting or not based on the presence of a close neighbour, the presence of stellar debris fields, disturbed discs, and/or tidal features. By inspecting the trajectories of the pairs, we determine that these indicators correctly identify interacting galaxies âź45 perâcent of the time. We subsequently split the sample into the visually identified interacting pairs (VIP; 38 pairs) and those which are interacting but are not visually identified (nonVIP; 47 pairs). We find that VIP have undergone a close passage nearly twice as recently as the non-VIP, and typically have higher stellar masses. Further, the VIP sit in dark matter haloes that are approximately 2.5 times as massive, in environments nearly 2 times as dense, and are almost a factor of 10 more affected by the tidal forces of their surroundings than the nonVIP. These factors conspire to increase the observability of tidal features and disturbed morphologies, making the VIP more likely to be identified. Thus, merger rate calculations which rely on stellar morphologies are likely to be significantly biased toward massive galaxy pairs which have recently undergone a close passage
Galaxy interactions in IllustrisTNG-100, I: The power and limitations of visual identification
We present a sample of 446 galaxy pairs constructed using the cosmological
simulation IllustrisTNG-100 at z = 0, with M =
10-10 M. We produce ideal mock SDSS g-band images of
all pairs to test the reliability of visual classification schema employed to
produce samples of interacting galaxies. We visually classify each image as
interacting or not based on the presence of a close neighbour, the presence of
stellar debris fields, disturbed discs, and/or tidal features. By inspecting
the trajectories of the pairs, we determine that these indicators correctly
identify interacting galaxies of the time. We subsequently split the
sample into the visually identified interacting pairs (VIP; 38 pairs) and those
which are interacting but are not visually identified (nonVIP; 47 pairs). We
find that VIP have undergone a close passage nearly twice as recently as the
nonVIP, and typically have higher stellar masses. Further, the VIP sit in dark
matter haloes that are approximately 2.5 times as massive, in environments
nearly 2 times as dense, and are almost a factor of 10 more affected by the
tidal forces of their surroundings than the nonVIP. These factors conspire to
increase the observability of tidal features and disturbed morphologies, making
the VIP more likely to be identified. Thus, merger rate calculations which rely
on stellar morphologies are likely to be significantly biased toward massive
galaxy pairs which have recently undergone a close passage.Comment: 20 pages, 11 figures, thumbnail catalog of interacting pairs sampl
Galaxy interactions in IllustrisTNG-100, I: The power and limitations of visual identification
We present a sample of 446 galaxy pairs constructed using the cosmological simulation IllustrisTNG-100 at z = 0, with M_(FoF,dm)=10ššâ10^(13.5) Mâ. We produce ideal mock SDSS g-band images of all pairs to test the reliability of visual classification schema employed to produce samples of interacting galaxies. We visually classify each image as interacting or not based on the presence of a close neighbour, the presence of stellar debris fields, disturbed discs, and/or tidal features. By inspecting the trajectories of the pairs, we determine that these indicators correctly identify interacting galaxies âź45 perâcent of the time. We subsequently split the sample into the visually identified interacting pairs (VIP; 38 pairs) and those which are interacting but are not visually identified (nonVIP; 47 pairs). We find that VIP have undergone a close passage nearly twice as recently as the non-VIP, and typically have higher stellar masses. Further, the VIP sit in dark matter haloes that are approximately 2.5 times as massive, in environments nearly 2 times as dense, and are almost a factor of 10 more affected by the tidal forces of their surroundings than the nonVIP. These factors conspire to increase the observability of tidal features and disturbed morphologies, making the VIP more likely to be identified. Thus, merger rate calculations which rely on stellar morphologies are likely to be significantly biased toward massive galaxy pairs which have recently undergone a close passage
Controls on pathogen species richness in plantsâ introduced and native ranges: roles of residence time, range size and host traits
Introduced species escape many pathogens and other enemies, raising three questions. How quickly do introduced hosts accumulate pathogen species? What factors control pathogen species richness? Are these factors the same in the hostsâ native and introduced ranges? We analysed fungal and viral pathogen species richness on 124 plant species in both their native European range and introduced North American range. Hosts introduced 400 years ago supported six times more pathogens than those introduced 40 years ago. In hostsâ native range, pathogen richness was greater on hosts occurring in more habitat types, with a history of agricultural use and adapted to greater resource supplies. In hostsâ introduced range, pathogen richness was correlated with host geographic range size, agricultural use and time since introduction, but not any measured biological traits. Introduced species have accumulated pathogens at rates that are slow relative to most ecological processes, and contingent on geographic and historic circumstance
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