[Astro] [CAPT] CAPT Weekly Bulletin (w/c 12-01-26)

[Ella Batchelor (staff)]

Tuesdays at 11am, CAPT Foyer – Astro Coffee

Tuesdays at 11.30am, A113 CAPT – Astronomy Journal Club
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Wednesday 14th January at 3.45pm, C4 Physics – Astronomy Weekly Seminar

Ilin Hazar (Herts)
Dwarf galaxies in deep-wide surveys: a new frontier in the study of galaxy evolution

Dwarf galaxies dominate the galaxy number density at all epochs and all environments, making them critical to our understanding of galaxy evolution. However, typical dwarfs are too faint to be visible outside the very local Universe in past surveys like the SDSS, which offer large footprints but are relatively shallow. In this study I use data from Ultra Deep layer (i<27.5 mag) of Hyper Suprime-Cam (which is around 10 magnitudes deeper than the SDSS spectroscopic sample) to present results on: (1) the morphological mix of the dwarf population in the nearby Universe, (2) the dwarf stellar mass function across different environments with a focus on the missing dwarf problem and (3) the galaxy red fraction and the validity of the “downsizing” phenomenon in the dwarf regime. Our dwarf samples are formed of dwarfs (M⋆ < 10^9.5 MSun) in the COSMOS and XMM-LSS fields reaching redshifts of z=0.4 and lower stellar mass limits of 10^7 MSun. We find that ~45 and ~45 per cent of dwarfs exhibit the traditional 'early-type' (elliptical/S0) and 'late-type' (spiral) morphologies, respectively. However, 10 per cent populate a 'featureless' class, that lacks both the central light concentration seen in early-types and any spiral structure - this class is missing in the massive-galaxy regime. Compared to their massive counterparts, dwarf early-types show a much lower incidence of interactions and are significantly less concentrated. This suggests that the formation histories of dwarf and massive early-types are different, with dwarf early-types being shaped less by interactions and more by secular processes. In addition, we find that it is challenging to cleanly separate early and late-type dwarfs using traditional morphological parameters such as ‘CAS’, M20 and the Gini coefficient (unlike in the massive galaxy regime). We find no evidence of a generic missing dwarf problem when all environments are considered (and not just satellites of Milky Way like galaxies). Finally, “downsizing” does not continue uninterrupted into the dwarf regime and the galaxy red fraction starts increasing again from M⋆ = 10^8.5 MSun towards lower stellar masses. I will end with presenting future prospects/plans for dwarf galaxy evolution studies in the era of Euclid and LSST.

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Thursday 15th January at 1pm, A113 CAPT – Astronomy Lunch Talk

Hua Gao

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Fridays at 4pm, CAPT Foyer – CAPT Cakes
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If you have any events/visitors you would like included in next week’s bulletin, please let me know.


Best wishes

Ella

Ella Batchelor (she/her)
Administrator

School of Physics & Astronomy

University of Nottingham
A112a Centre for Astronomy & Particle Theory
University Park
Nottingham, NG7 2RD

+44 (0) 115 74 86778 |  nottingham.ac.uk<http://nottingham.ac.uk/>

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