Scaling relations for globular cluster systems in early-type galaxies

Abstract

The formation and growth of globular cluster systems (GCSs) is closely related to the evolutionary processes experienced by their host galaxies. In particular, their radial distributions scale with several properties of the galaxies and their halos. We performed a photometric study, by means of HST/ACS archival data of several intermediate luminosity galaxies located in low density environments. It was supplemented with available photometric data of GCSs from the Virgo and Fornax clusters, resulting in a sample of almost 30 GCSs for which we fitted their radial profiles. The resulting overall properties agree with those from previous studies, as we found that the effective radius, extension and concentration of the GCS radial profiles correlate with the stellar mass, effective radius and number of globular clusters, presenting in some cases a bilinear relation. The extension also correlates with the central velocity dispersion for central galaxies, but not for satellites. From a statistical comparison with numerical simulations we obtained good agreement between the effective radius and extension of the GCS scale with the effective and virial radius of the halos, respectively. Finally, we analysed these results in the literature context.

Wide-field study of the peculiar globular cluster system hosted by the field lenticular NGC 1172

“…In the case of NGC 1172, its metallicity has not been studied in detail, but there is enough data to explore its colour. It has a magnitude of M g = −19.58 mag considering the distance adopted in this paper, and from Caso et al (2019b) we obtain (g − z ) 0 = 1.22 mag. Ferrarese et al (2006) analysed the colour-magnitude relation for a significant number of ETGs in the Virgo Cluster and, using this relation, we obtain an expected value of (g − z ) 0 = 1.45 mag for NGC 1172.…”

“…This fit does not take into account the flattening, which is why we also fit a modified version of the Hubble-Reynolds law (Binney & Tremaine 1987;Dirsch et al 2003), described in Equation 3. In Caso et al (2019b), the same modified Hubble profile is fitted only to the ACS sample (Cho et al 2012), and the parameters are consistent, as shown in 2.…”

“…Completeness was calculated dividing the region in rings at different galactocentric distances, as to take into consideration differential effects in the radial distribution. Further information about the photometry of this dataset can be found in Caso et al (2019b).…”

The first detection of ultra-diffuse galaxies in the Hydra I cluster from the VEGAS survey

“…Adopting the approach suggested by van Dokkum et al (2016), we estimated the total population within 1.5R e . In addition, the total number of GCs within 5 R e , which is the upper limit for bound systems (Kartha et al 2014;Forbes 2017;Caso et al 2019), is also derived. Since the photometry reaches roughly the TOM peak, and assuming that the GCLF is also a Gaussian for the UDGs (e.g.…”

Formation of an ultra-diffuse galaxy in the stellar filaments of NGC 3314A: Caught in the act?

“…We find that the number of GC candidates over the ∼ 10.5 × 9.5 area around the UDG is ∼ 3.0 ± 3 arcmin −2 . The total number of GCs (N GC ) was derived within 1.5 R e , adopting the approach suggested by van Dokkum et al (2016), and also within 3 and 5R e , the higher value being close to the upper limit for bound systems (Forbes 2017;Caso et al 2019). All estimates were corrected for the contamination of foreground stars, background galaxies, and possible intra-cluster GCs, which is ∼ 3 sources/arcmin 2 , derived in the regions between 5 ≤ R ≤ 10 around the UDG.…”