The first confirmed UCD in the NGC 5044 Group

FAIFER, F.; ESCUDERO, C.; SESTO, L.; SCALIA, M. C.; SMITH CASTELLI, A.

Córdoba

Congreso; Terceras Jornadas de Astrofísica Estelar; 2016

Observatorio Astronómico de Córdoba

Ultra­compact  dwarf  galaxies  (UCDs)  are  stellar  objects  with  shared  features  between  globular  cluster  (GC)  and  dwarf galaxies  (colors,  metallicities,  etc),  with  sizes  of  Re  ≤  100  pc,  and  luminosities  of  −13.5  <  MV  <  −9,  (Brodie  et  al.  2011). Although  its  mechanism  of  formation  is  still  subject  of  debate,  current  scenarios  suggest  that  it  may  be  massive  star clusters (possibly as a result of fusion processes), or the nuclei of tidally stripped dwarf galaxies (eg, Longmore et al. 2014, Brodie et al. 2011, Hilker 2009, Pfeffer et al. 2014). Therefore, in this work we have focused on the analysis of an UCD (red arrow  in  Figure  1)  located  in  the  system  of  the  massive  elliptical  galaxy  NGC  5044  (M B  =  ?21.2).  This  galaxy,  with  a distance of 35.7±5 Mpc (mean value provided by NED) and with a systemic velocity of Vr = 2782 km s ­1, is the central object of  the  group  (also  considered  as  a  small  cluster  of  galaxies),  known  as  NGC  5044.  This  group  has  about  150  members, mostly dwarf galaxies (Ferguson & Sandage 1990). NGC 5044 presents a rich GC system (about 5000 members) and several UCD  candidates.  From  the  photometric  analysis  of  four  deep  fields  taken  with  Gemini+GMOS,  and  the  spectroscopic analysis  of  one  field,  we could  confirm  the  presence  of  an  UCD  (MV  ~  ?12.3 mag)  through  the  determination  of  its  radial velocity.