UA cloudflare authentication

Browsing by Author "Dupke, R."

Now showing 1 - 3 of 3
  • Thumbnail Image
    Item
    Assessing the reliability of friends-of-friends groups on the future Javalambre Physics of the Accelerating Universe Astrophysical Survey
    (EDP Sciences, 2014) Zandivarez, A.; Diaz-Gimenez, E.; Mendes de Oliveira, C.; Ascaso, B.; Benitez, N.; Dupke, R.; Sodre, L., Jr.; Irwin, J.; Consejo Nacional de Investigaciones Cientificas y Tecnicas (CONICET); National University of Cordoba; Universidade de Sao Paulo; Consejo Superior de Investigaciones Cientificas (CSIC); CSIC - Instituto de Astrofisica de Andalucia (IAA); University of Michigan System; University of Michigan; Eureka Scientific; University of Alabama Tuscaloosa
    Aims. We have performed a detailed analysis of the ability of the friends-of-friends algorithm to identify real galaxy systems in deep surveys such as the future Javalambre Physics of the Accelerating Universe Astrophysical Survey. Our approach was twofold: assessing the reliability of the algorithm in real and in redshift space. In the latter, our intention was also to determine the degree of accuracy that could be achieved when using spectroscopic or photometric-redshift determinations as a distance indicator. Methods. We built a light-cone mock catalogue using synthetic galaxies constructed from the Millennium Run Simulation I plus a semi-analytical model of galaxy formation. We explored different ways to define the proper linking length parameters of the algorithm to identify the best-suited galaxy groups in each case. Results. We found that when one identifies systems in redshift space using spectroscopic information, the linking lengths should take into account the variation of the luminosity function with redshift as well as the linear redshift dependence of the radial fiducial velocity in the line-of-sight direction. When we tested the purity and completeness of the group samples, we found that the best resulting group sample reaches values of similar to 40% and similar to 70% of systems with high levels of purity and completeness, when spectroscopic information was used. To identify systems using photometric redshifts, we adopted a probabilistic approach to link galaxies in the line-of-sight direction. Our result suggests that it is possible to identify a sample of groups with fewer than similar to 40% false identifications at the same time as we recover around 60% of the true groups. Conclusions. This modified version of the algorithm can be applied to deep surveys provided that the linking lengths are selected appropriately for the science to be made with the data.
  • Thumbnail Image
    Item
    Deep spectroscopy of the M-V similar to-14.8 host galaxy of a tidal disruption flare in A1795
    (Oxford University Press, 2014) Maksym, W. P.; Ulmer, M. P.; Roth, K. C.; Irwin, J. A.; Dupke, R.; Ho, L. C.; Keel, W. C.; Adami, C.; University of Alabama Tuscaloosa; Northwestern University; University of Michigan System; University of Michigan; Eureka Scientific; Peking University; Carnegie Institution for Science; UDICE-French Research Universities; Aix-Marseille Universite
    A likely tidal disruption of a star by the intermediate-mass black hole (IMBH) of a dwarf galaxy was recently identified in association with Abell 1795. Without deep spectroscopy for this very faint object, however, the possibility of a more massive background galaxy or even a disc-instability flare from a weak active galactic nucleus (AGN) could not be dismissed. We have now obtained 8 h of Gemini spectroscopy which unambiguously demonstrates that the host galaxy is indeed an extremely low mass (M-star similar to 3 x 10(8) M-circle dot) galaxy in Abell 1795, comparable to the least massive galaxies determined to host IMBHs via other studies. We find that the spectrum is consistent with the X-ray flare being due to a tidal disruption event rather than an AGN flare. We also set improved limits on the black hole mass (log[M-lozenge/M-circle dot] similar to 5.3-5.7) and infer a 15 yr X-ray variability of a factor of greater than or similar to 10(4). The confirmation of this galaxy-black hole system provides a glimpse into a population of galaxies that is otherwise difficult to study, due to the galaxies' low masses and intrinsic faintness, but which may be important contributors to the tidal disruption rate.
  • Thumbnail Image
    Item
    Deep spectroscopy of the M-V similar to-14.8 host galaxy of a tidal disruption flare in A1795
    (Oxford University Press, 2014) Maksym, W. P.; Ulmer, M. P.; Roth, K. C.; Irwin, J. A.; Dupke, R.; Ho, L. C.; Keel, W. C.; Adami, C.; University of Alabama Tuscaloosa; Northwestern University; University of Michigan System; University of Michigan; Eureka Scientific; Peking University; Carnegie Institution for Science; UDICE-French Research Universities; Aix-Marseille Universite
    A likely tidal disruption of a star by the intermediate-mass black hole (IMBH) of a dwarf galaxy was recently identified in association with Abell 1795. Without deep spectroscopy for this very faint object, however, the possibility of a more massive background galaxy or even a disc-instability flare from a weak active galactic nucleus (AGN) could not be dismissed. We have now obtained 8 h of Gemini spectroscopy which unambiguously demonstrates that the host galaxy is indeed an extremely low mass (M-star similar to 3 x 10(8) M-circle dot) galaxy in Abell 1795, comparable to the least massive galaxies determined to host IMBHs via other studies. We find that the spectrum is consistent with the X-ray flare being due to a tidal disruption event rather than an AGN flare. We also set improved limits on the black hole mass (log[M-lozenge/M-circle dot] similar to 5.3-5.7) and infer a 15 yr X-ray variability of a factor of greater than or similar to 10(4). The confirmation of this galaxy-black hole system provides a glimpse into a population of galaxies that is otherwise difficult to study, due to the galaxies' low masses and intrinsic faintness, but which may be important contributors to the tidal disruption rate.