Browsing by Author "Collins, C. A."

Now showing 1 - 2 of 2
  • No Thumbnail Available
    Item
    Gravitational redshifting of galaxies in the SPIDERS cluster catalogue
    (2021) Mpetha, C. T.; Collins, C. A.; Clerc, N.; Finoguenov, A.; Peacock, J. A.; Comparat, J.; Schneider, D.; Capasso, R.; Damsted, S.; Furnell, K.; Merloni, A.; Padilla, N. D.; Saro, A.
    Data from the SPectroscopic IDentification of ERosita Sources (SPIDERS) are searched for a detection of the gravitational redshifting of light from similar to 20 000 galaxies in similar to 2500 galaxy clusters using three definitions of the cluster centre: its Brightest Cluster Galaxy (BCG), the redMaPPer identified Central Galaxy (CG), or the peak of X-ray emission. Distributions of velocity offsets between galaxies and their host cluster's centre, found using observed redshifts, are created. The quantity (Delta) over cap, the average of the radial velocity difference between the cluster members and the cluster systemic velocity, reveals information on the size of a combination of effects on the observed redshift, dominated by gravitational redshifting. The change of (Delta) over cap with radial distance is predicted for SPIDERS galaxies in General Relativity (GR), and f(R) gravity, and compared to the observations. The values of (Delta) over cap = -13.5 +/- 4.7 kms(-1), (Delta) over cap = -12.5 +/- 5.1 kms(-1), and (Delta) over cap = -18.6 +/- 4.8 kms(-1) for the BCG, X-ray, and CG cases, respectively, broadly agree with the literature. There is no significant preference of one gravity theory over another, but all cases give a clear detection (>2.5 sigma) of (Delta) over cap. The BCG centroid is deemed to be the most robust method in this analysis, due to no well-defined central redshift when using an X-ray centroid, and CGs identified by redMaPPer with no associated spectroscopic redshift. For future gravitational redshift studies, an order-of-magnitude more galaxies, similar to 500 000, will be required - a possible feat with the forthcoming Vera C. Rubin Observatory, Euclid and eROSITA.
  • No Thumbnail Available
    Item
    Preparing for low surface brightness science with the Vera C. Rubin Observatory: Characterization of tidal features from mock images
    (2022) Martin, G.; Bazkiaei, A. E.; Spavone, M.; Iodice, E.; Mihos, J. C.; Montes, M.; Benavides, J. A.; Brough, S.; Carlin, J. L.; Collins, C. A.; Duc, P. A.; Gomez, F. A.; Galaz, G.; Hernandez-Toledo, H. M.; Jackson, R. A.; Kaviraj, S.; Knapen, J. H.; Martinez-Lombilla, C.; McGee, S.; O'Ryan, D.; Prole, D. J.; Rich, R. M.; Roman, J.; Shah, E. A.; Starkenburg, T. K.; Watkins, A. E.; Zaritsky, D.; Pichon, C.; Armus, L.; Bianconi, M.; Buitrago, F.; Busa, I; Davis, F.; Demarco, R.; Desmons, A.; Garcia, P.; Graham, A. W.; Holwerda, B.; Hon, D. S-H; Khalid, A.; Klehammer, J.; Klutse, D. Y.; Lazar, I; Nair, P.; Noakes-Kettel, E. A.; Rutkowski, M.; Saha, K.; Sahu, N.; Sola, E.; Vazquez-Mata, J. A.; Vera-Casanova, A.; Yoon, I
    Tidal features in the outskirts of galaxies yield unique information about their past interactions and are a key prediction of the hierarchical structure formation paradigm. The Vera C. Rubin Observatory is poised to deliver deep observations for potentially millions of objects with visible tidal features, but the inference of galaxy interaction histories from such features is not straightforward. Utilizing automated techniques and human visual classification in conjunction with realistic mock images produced using the NewHorizon cosmological simulation, we investigate the nature, frequency, and visibility of tidal features and debris across a range of environments and stellar masses. In our simulated sample, around 80 per cent of the flux in the tidal features around Milky Way or greater mass galaxies is detected at the 10-yr depth of the Legacy Survey of Space and Time (30-31 mag arcsec(-2)), falling to 60 per cent assuming a shallower final depth of 29.5 mag arcsec(-2). The fraction of total flux found in tidal features increases towards higher masses, rising to 10 per cent for the most massive objects in our sample (M-* similar to 10(11.5) M-circle dot). When observed at sufficient depth, such objects frequently exhibit many distinct tidal features with complex shapes. The interpretation and characterization of such features varies significantly with image depth and object orientation, introducing significant biases in their classification. Assuming the data reduction pipeline is properly optimized, we expect the Rubin Observatory to be capable of recovering much of the flux found in the outskirts of Milky Way mass galaxies, even at intermediate redshifts (z < 0.2).