The spatial distribution of dwarf and giant galaxies in and around Virgo cluster

TL;DR

This work investigates how dwarf and giant galaxies are spatially distributed around the Virgo cluster and how the dwarf fraction $DF = N_d/(N_g+N_d)$ varies with environment, using three large catalogues (EVCC, NSA-Castignani, and Hyperleda-based Makarov2011) to cover both cluster and surrounding filaments. Dwarf and giant populations are selected with catalogue-specific luminosity thresholds, enabling a consistent DF mapping from the cluster core to large-scale filaments. The results show that inside $R_{200}$ the global DF is about 0.8 but exhibits significant local variation tied to substructures; on larger scales, DF is higher in low-density regions and filaments, with environmental dependence further modulated by the presence of groups within filaments. These findings imply a dynamic assembly where filaments feed the cluster with both dwarfs and giants, while tidal processes in dense regions can suppress or rearrange the dwarf population, suggesting future hydrodynamical simulations to track these processes over time.

Abstract

The Virgo cluster is one of the closest clusters to us where we can further study the evolution of galaxies, with several infalling substructures and several filaments around it have been reported. Therefore, it makes this cluster and its surrounding an interesting place to study the spatial distribution of the population of dwarf and bright giant galaxies. We analyse the dwarf fraction (DF) in different regions of the cluster, inside the virial radius, in its surrounding area, and in the filamentary structure surrounding it using available catalogues with the aim of measuring whether the DF changes in different environments. Although the total dwarf fraction within the cluster is $\sim$ 0.8, significant local variations are measured throughout the cluster; there are regions with a relatively higher concentration of giant or dwarf galaxies. The fact that Virgo is embedded in a rich environment surrounded by several filaments that feed the cluster with new substructures could imply changes in the DF locally. When we analyse the DF variation at further distances from the cluster we observe some regions with few or no giant galaxies at all, with a locally DF ranging from 0.8 - 1.0. Additionally, when comparing the dwarf fraction in different environments, overall, the DF is larger in regions further away from denser regions such as the Virgo cluster and its filamentary structure surrounding it. When comparing the filament and the cluster area, the dwarf fraction is slightly higher in the filaments, but from filament to filament, the DF changes depending on the presence of groups.

Figures (10)

• Figure 1: Absolute magnitude range of galaxies in the EVCC ($r$-band, left panel), NSA-Castignani ($r$-band, middle panel), and Hyperleda ($K$-band, right panel) catalogues. Red dashed line indicates the threshold limit that we use to separate giant (left side) from dwarf (right side) galaxies in the EVCC and NSA catalogues. Rightmost blue dashed line marks the limit imposed on dwarf galaxies to ensure the completeness of magnitudes of each catalogue. The blue dashed lines in the third panel indicates the M$_k$ range to select dwarf galaxies in the Hyperleda catalogue. Note that absolute magnitudes are measured at the distance of Virgo.
• Figure 2: Left panel: Projected spatial distribution of dwarfs (blue open symbols) and giants (red filled symbols) from the EVCC catalogue. Black cross indicates the position of M87 galaxy. Dashed circle indicates the R$_{200}$ region of Virgo cluster. Middle panel: Cumulative distributions of the clustercentric distance of giant and dwarf galaxies inside R$_{200}$ of Virgo cluster. Note that in both panels the galaxy distribution is limited to M$_r$ = -14 mag. Right panel: Dwarf fraction (DF, measured in bins of distance) as a function of projected cluster-centric distance, measured for the EVCC catalogue without magnitude threshold (dashed line) and for galaxies up to an absolute magnitude, M$_r$ = -14 mag (filled line).
• Figure 3: Galaxy spatial distribution in the EVCC area. Red circle highlights the R$_{200}$ radius of the Virgo cluster. Left: DF in the cluster region. Right: DF in the entire field of view of the EVCC catalogue. Grey circles highlight the groups from the galaxy group catalogue of Kourkchi2017. The northern grey lines highlights the filaments of the Castinagni2022 catalogue. The two filaments in the south were extracted from Fig. 2 of Castignani2022a. The colour bar in both panels denotes the dwarf fraction (DF) associated with each galaxy, as quantified by considering its fifteen nearest neighbours.
• Figure 4: Galaxy spatial projected distribution in the large scale structure around Virgo (northern hemisphere) from the NSA-Castignani catalogue Castinagni2022. Colour indicates the local DF measured on each galaxy in the region enclosing its fifteen near neighbour galaxies. Red circle highlights the R$_{200}$ radius of the Virgo cluster, while grey circles highlight the (loose and rich) groups from the galaxy group catalogue of Kourkchi2017 (in the velocity range 500 $<$$v_r$$<$ 3300 km/s; the circle sizes correspond to the projected virial radius of the groups described in that work). The grey lines highlights the filaments of the Castignani2022aCastinagni2022 catalogue; Leo Minor F, Canes Venatici F, Bootes F, Ursa Major Cloud, Leo II B F, Leo II A F, Virgo III F , Leo Minor B F, W–M Sheet, NGC 5353/4 F, Serpens F, Draco F, and Coma Berenices F.
• Figure 5: Galaxy spatial projected distribution in the large scale structure around Virgo (including the southern hemisphere) from the Hyperleda catalogue described in Makarov2011. Colour indicates the DF on each galaxy measured in the region containing the fifteen near neighbour galaxies. Red circle highlights the Virgo cluster, while grey circles highlight the (loose and rich) groups from the galaxy group catalogue of Kourkchi2017 (in the velocity range 500 $<$$v_r$$<$ 3300 km/s). The grey lines highlights the filaments of the Castinagni2022 catalogue. Note that all the filaments reported in Castinagni2022 are plotted the figure; Leo Minor F, Canes Venatici F, Bootes F, Ursa Major Cloud, Leo II B F, Leo II A F, Virgo III F , Leo Minor B F, W–M Sheet, NGC 5353/4 F, Serpens F, Draco F, and Coma Berenices F. The two filaments in the south: Virgo Southern Extension and Crater were extracted from Castignani2022a.