New KiDS in town

Astronomy and Astrophysics, vol. 681, pp. L13

Abstract

We report the discovery of a significant and compact over-density of old and metal-poor stars in the fourth data release of the KiDS survey (DR4). The discovery is confirmed by deeper HSC-SSP data revealing the old main sequence turn-off of a stellar system located at a distance from the sun of D⊙ = 145-13+14 kpc in the direction of the Sextans constellation. The system has an absolute integrated magnitude (MV = −3.9 ± 0.4), half-light radius (rh = 193-46+61 pc), and ellipticity (e = 0.46-0.15+0.11) values that are typical of ultra-faint dwarf galaxies (UFDs). The central surface brightness is near the lower limits of known local dwarf galaxies of a similar integrated luminosity, as expected for stellar systems that have escaped detection until now. The distance of the newly found system suggests that it is likely to be a satellite of our own Milky Way and we have thus tentatively named it Sextans II (KiDS-UFD-1).

Authors 12

1. M. Gatto

   Astronomical Observatory of Capodimonte · National Institute for Astrophysics

   Affiliation as printed

   INAF-Osservatorio Astronomico di Capodimonte, Via Moiariello, 16, 80131 Napoli, Italy

2. M. Bellazzini

   Osservatorio di Astrofisica e Scienza dello Spazio · National Institute for Astrophysics

   Affiliation as printed

   INAF-Osservatorio di Astrofisica e Scienza dello Spazio, Via Gobetti, 93/3, 40129 Bologna, Italy

3. C. Tortora

   Astronomical Observatory of Capodimonte · National Institute for Astrophysics

   Affiliation as printed

   INAF-Osservatorio Astronomico di Capodimonte, Via Moiariello, 16, 80131 Napoli, Italy

4. V. Ripepi

   Astronomical Observatory of Capodimonte · National Institute for Astrophysics

   Affiliation as printed

   INAF-Osservatorio Astronomico di Capodimonte, Via Moiariello, 16, 80131 Napoli, Italy

5. Massimo Dall’Ora

   Astronomical Observatory of Capodimonte · National Institute for Astrophysics

   Affiliation as printed

   INAF-Osservatorio Astronomico di Capodimonte, Via Moiariello, 16, 80131 Napoli, Italy

6. M. Cignoni

   University of Pisa · Astronomical Observatory of Capodimonte · Istituto Nazionale di Fisica Nucleare, Sezione di Pisa · National Institute for Astrophysics

   Affiliation as printed

   INAF-Osservatorio Astronomico di Capodimonte, Via Moiariello, 16, 80131 Napoli, Italy

   INFN-Largo Bruno Pontecorvo 3, 56127 Pisa, Italy

   Physics Department, University of Pisa, Largo Bruno Pontecorvo 3, 56127 Pisa, Italy

7. Konrad H. Kuijken Aachen Leiden Observatory

   Leiden University · Leiden Observatory

   Affiliation as printed

   Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands

8. Hendrik Hildebrandt

   Ruhr University Bochum

   Affiliation as printed

   Ruhr University Bochum, Faculty of Physics and Astronomy, Astronomical Institute (AIRUB), German Centre for Cosmological Lensing, 44780 Bochum, Germany

9. Shiyang Zhang

   Ruhr University Bochum

   Affiliation as printed

   Ruhr University Bochum, Faculty of Physics and Astronomy, Astronomical Institute (AIRUB), German Centre for Cosmological Lensing, 44780 Bochum, Germany

10. J. T. A. de Jong Aachen Leiden Observatory

    Leiden University · University of Groningen · Leiden Observatory

    Affiliation as printed

    Kapteyn Astronomical Institute, University of Groningen, PO Box 800, 9700 AV Groningen, The Netherlands

    Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands

11. Nicola R. Napolitano

    Sun Yat-sen University

    Affiliation as printed

    School of Physics and Astronomy, Sun Yat-sen University, Guangzhou, 519082 Zhuhai Campus, PR China

12. Simon E. T. Smith

    University of Victoria

    Affiliation as printed

    Department of Physics and Astronomy, University of Victoria, Victoria, BC V8P 1A1, Canada