Tracing the assembly history of NGC 1395 through its Globular Cluster System

Abstract

We used deep Gemini-South/GMOS g ′ r ′ i ′ z ′ images to study the globular cluster (GC) system of the massive elliptical galaxy NGC 1395, located in the Eridanus supergroup. The photometric analysis of the GC candidates reveals a clear colour bimodality distribution, indicating the presence of "blue" and "red" GC subpopulations. While a negative radial colour gradient is detected in the projected spatial distribution of the red GCs, the blue GCs display a shallow colour gradient. The blue GCs also display a remarkable shallow and extended surface density profile, suggesting a significant accretion of low-mass satellites in the outer halo of the galaxy. In addition, the slope of the projected spatial distribution of the blue GCs in the outer regions of the galaxy, is similar to that of the X-ray halo emission. Integrating up to 165 kpc the profile of the projected spatial distribution of the GCs, we estimated a total GC population and specific frequency of 6000±1100 and S N =7.4±1.4, respectively. Regarding NGC 1395 itself, the analysis of the deep Gemini/GMOS images shows a low surface brightness umbrella-like structure indicating, at least, one recent merger event. Through relations recently published in the literature, we obtained global parameters, such as M stellar = 9.32 × 10 11 M⊙ and M h = 6.46 × 10 13 M⊙. Using public spectroscopic data, we derive stellar population parameters of the central region of the galaxy by the full spectral fitting technique. We have found that, this region, seems to be dominated for an old stellar population, in contrast to findings of young stellar populations from the literature.

A supragalactic conundrum: the globular clusters colour pattern in Virgo galaxies

“…In this case the feature at [0.85] is barely detectable. This is consistent with results available in the literature (see, for example, Escudero et al 2018) showing that the inner regions of giant galaxies are usually dominated by red GCs while the bluer globulars are less abundant. Fig.…”

Field/isolated lenticular galaxies with high SN values: the case of NGC 4546 and its globular cluster system

“…It is known that "blue" and "red" GCs have different 2D spatial distribution in the sense that blue GCs have more extended and less concentrated distribution than the red GCs (e.g., Usher et al 2013;Harris et al 2017;Escudero et al 2018). Analyzing the spatial concentration toward the galaxy of the different samples of GCs candidates can help us to evaluate the reliability of our selection criteria.…”

“…Based on the information obtained from the surface density profile of the whole GC sample and from the GCLF analysis, we estimate the total GC population and the specific frequency (SN ) of NGC 4546. For this, we follow the same procedure as in Escudero et al (2015Escudero et al ( , 2018. We integrated the density profile from 0.26 arcmin up to the galactocentric radius of 12.3 arcmin, equivalent to 50 kpc.…”

A Gemini/GMOS study of the bright elliptical galaxy NGC 3613 and its globular cluster system

“…• different projected spatial distribution with respect to the host galaxy, with red GCs being generally more concentrated towards the centre of the host galaxies and tracing their surface-brightness profiles, while blue ones present a more extended distribution (e.g. Bassino et al 2006;Forbes et al 2012;Durrell et al 2014;Escudero et al 2018).…”