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Register a new userAbell 2626 and friends: large and small scale structure
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New MMT/Hectospec spectroscopy centered on the galaxy cluster A2626 and covering a ${sim} 1.8,text{deg}^2$ area out to $z sim 0.46$ more than doubles the number of galaxy redshifts in this region. The spectra confirm four clusters previously identified photometrically. A2625, which was previously thought to be a close neighbor of A2626, is in fact much more distant. The new data show six substructures associated with A2626 and five more associated with A2637. There is also a highly collimated collection of galaxies and galaxy groups between A2626 and A2637 having at least three and probably four substructures. At larger scales, the A2626--A2637 complex is not connected to the Pegasus--Perseus filament.
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The morphology-density relation manifests the environmental dependence of the formation and evolution of galaxies as they continuously migrate through the cosmic web to ever denser environments. As gas-rich galaxies traverse the outskirts and inner regions of galaxy clusters they experience sudden and radical changes in their gas content and star formation activity. The goal of this work is to gain an H$,$I perspective on gas depletion mechanisms acting on galaxies and galaxy groups that are being accreted by a moderately massive galaxy cluster. We aim to study the relative importance and efficiency of processes such as ram-pressure stripping and tidal interactions as well as their dependency on the local and global environment of galaxies in the cluster core and in its surroundings. We have conducted a blind radio continuum and H$,$I spectral line imaging survey with the MeerKAT radio telescope of a 2$^circ$ $times$ 2$^circ$ area centred on the galaxy cluster Abell 2626. We have used the CARAcal pipeline to reduce the data, SoFiA to detect sources within the H$,$I data cube, and GIPSY to construct spatially resolved information on the H$,$I morphologies and kinematics of the H$,$I detected galaxies. We have detected H$,$I in 219 galaxies with optical counterparts within the entire surveyed volume. We present the H$,$I properties of each of the detected galaxies as a data catalogue and as an atlas page for each galaxy, including H$,$I column-density maps, velocity fields, position-velocity diagrams and global H$,$I profiles. These data will also be used for case studies of identified ``jellyfish galaxies and galaxy population studies by means of morphological classification of the direct H$,$I detections as well as using the H$,$I stacking technique.
This paper presents the analysis of a combined 134 ks {it Chandra} data of a peculiar galaxy cluster Abell 2626. This study confirms the earlier detection of the east cavity at $sim$13 kpc and reports detection of a new cavity at $sim$39 kpc on the west of the X-ray peak. The average mechanical power injected by the AGN outburst ${rm P_{cav} sim 6.6 times 10^{44}, erg, s^{-1}}$ is $sim$29 times more than required to compensate the cooling luminosity ${rm L_{cool} = 2.30 pm 0.02 times 10^{43} {rm~erg s}^{-1}}$. The edges in the SB on the west and south-west at $sim$36 kpc and 33 kpc, respectively, have the gas compressions of 1.57$pm$0.08 and 2.06$pm$0.44 and are spatially associated with the arcs in the temperature and metallicity maps due to the merging cold fronts. The systematic study of the nuclear sources exhibited dramatic changes over the span of ten years. The NE source that emitted mostly in the soft band in the past disappeared in the recent observations. Instead, an excess emission was seen at $2.2$ on its west and required an unrealistic line of sight velocity of $sim$ $675times{}c$ if is due to its movement. The count rate analysis and spectral analysis exhibited a change in the state of the SW source from a soft state to the hard due to the change in the mass accretion rate. No such spectral change was noticed for the NE source.
Studying the environments of 0.4<z<1.2 UV-selected galaxies, as examples of extreme star-forming galaxies (with star formation rates in the range of 3-30 M_sol/yr), we explore the relationship between high rates of star-formation, host halo mass and pair fractions. We study the large-scale and small-scale environments of local Ultraviolet Luminous Galaxies (UVLGs) by measuring angular correlation functions. We cross-correlate these systems with other galaxy samples: a volume-limited sample (ALL), a Blue Luminous Galaxy sample (BLG) and a Luminous Red Galaxy sample (LRG). We determine the UVLG comoving correlation length to be r_0=4.8(+11.6/-2.4) h^-1 Mpc at <z> =1.0, which is unable to constrain the halo mass for this sample. However, we find that UVLGs form close (separation < 30 kpc) pairs with the ALL sample, but do not frequently form pairs with LRGs. A rare subset of UVLGs, those with the highest FUV surface brightnesses, are believed to be local analogs of high redshift Lyman Break Galaxies (LBGs) and are called Lyman Break Analogs (LBAs). LBGs and LBAs share similar characteristics (i.e., color, size, surface brightness, specific star formation rates, metallicities, and dust content). Recent HST images of z~0.2 LBAs show disturbed morphologies, signs of mergers and interactions. UVLGs may be influenced by interactions with other galaxies and we discuss this result in terms of other high star-forming, merging systems.
The evolution and spatial structure of displacement fronts in fractures with self-affine rough walls are studied by numerical simulations. The fractures are open and the two faces are identical but shifted along their mean plane, either parallel or perpendicular to the flow. An initially flat front advected by the flow is progressively distorted into a self-affine front with Hurst exponent equal to that of the fracture walls. The lower cutoff of the self-affine regime depends on the aperture and lateral shift, while the upper cutoff grows linearly with the width of the front.
The adiabatic perturbation of dark matter is damped during the kinetic decoupling due to the collision with relativistic component on sub-horizon scales. However the isocurvature part is free from damping and could be large enough to make a substantial contribution to the formation of small scale structure. We explicitly study the weakly interacting massive particles as dark matter with an early mater dominated period before radiation domination and show that the isocurvature perturbation is generated during the phase transition and leaves imprint in the observable signatures for small scale structure.
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