Redshift Measurements for Galaxies in Clusters by Multislit Spectroscopy at the 1.5-m Telescope RTT150

  • PDF / 1,680,230 Bytes
  • 11 Pages / 612 x 792 pts (letter) Page_size
  • 20 Downloads / 186 Views

DOWNLOAD

REPORT


hift Measurements for Galaxies in Clusters by Multislit Spectroscopy at the 1.5-m Telescope RTT150 I. M. Khamitov1, 2* , I. F. Bikmaev2, 3 , R. A. Burenin4 , M. V. Glushkov2, 3 , S. S. Melnikov2, 3 , and A. R. Lyapin4 ¨ ITAK ´ TUB National Observatory, Antalya, Turkey Kazan Federal University, ul. Kremlevskaya 18, Kazan, 420000 Russia 3 Academy of Sciences of Tatarstan, ul. Baumana, 20, Kazan, Russia 4 Space Research Institute, ul. Profsoyuznaya 84/32, Moscow, 117997 Russia 1

2

Received December 4, 2019; revised December 4, 2019; accepted December 5, 2019

Abstract—An example of simultaneous spectroscopic redshift measurements for a large number of galaxies in a cluster by multiobject spectroscopy with the medium- and low-resolution TFOSC spectrograph at the Russian–Turkish 1.5-m telescope (RTT150) is presented. The redshifts of galaxies in the cluster 0301.6 + 0156 at z = 0.17057 ± 0.0004 detected previously by the Sunyaev–Zeldovich signal in the Planck all-sky survey have been measured. The spectra of 16 cluster galaxies, 9 of which were determined as ellipticals, were taken in one observation with an exposure time of 3 h and high-quality redshift measurements were made for them. We show that the redshifts of galaxies with magnitudes to mr = 20.0, whose number in the TFOSC field can reach dozens, depending on the cluster richness and distance, can be measured in one observation with the TFOSC spectrograph using multiobject masks. Such measurements may be required to refine the redshifts of clusters and to estimate their masses by the dynamical method. DOI: 10.1134/S106377372001003X Keywords: galaxy clusters, multiobject spectroscopy, optical observations.

INTRODUCTION

Zeldovich 1972) with the Planck Space Observatory (Planck Collaboration 2014a, 2015a, 2015b, 2016a, 2016b; Vorobyev et al. 2016; Burenin 2017; Burenin et al. 2018; Zaznobin et al. 2019). Spectroscopic redshift measurements for identified galaxy clusters are carried out at RTT150 mainly for systems at redshifts z < 0.4. The redshifts are estimated through spectroscopic observations of several brightest members at the cluster center or by observing only one brightest galaxy at the cluster center with a regular shape. This approach is determined by the efficiency of using the observing time of middleclass telescopes with mirror diameters of 1–2 m for such objects. The accuracy of redshift measurements achieved in this way (δz ∼ 0.001) for the galaxy clusters being studied is sufficient for their use in research on constraining the cosmological parameters. Since the brightest galaxy is virtually at the cluster center of mass, the measured redshift corresponds to the cluster redshift. Fainter galaxies are used only to confirm the red sequence on the color–luminosity diagram, based on which a preliminary identification of the cluster and its members is carried out. However, if the individual radial velocities of the galax-

Galaxy clusters occupy an important place in studying the large-scale structure of the Universe. The observed number of galaxy clusters of a