Placeholder image for staff profiles

Dr Denis Erkal

Lecturer of Astrophysics
+44 (0)1483 686990
12 BC 03

Academic and research departments

Astrophysics Research Group.


Media Contacts

Contact the press team


Phone: +44 (0)1483 684380 / 688914 / 684378
Out-of-hours: +44 (0)7773 479911
Senate House, University of Surrey
Guildford, Surrey GU2 7XH

My publications


Koposov Sergey E, Walker Matthew G, Belokurov Vasily, Casey Andrew R, Geringer-Sameth Alex, Mackey Dougal, Da Costa Gary, Erkal Denis, Jethwa Prashin, Mateo Mario, Olszewski Edward W, Bailey III John I (2018) Snake in the Clouds: A new nearby dwarf galaxy in the Magellanic bridge, Monthly Notices of the Royal Astronomical Society Oxford University Press
We report the discovery of a nearby dwarf galaxy in the constellation of Hydrus,
between the Large and the Small Magellanic Clouds. Hydrus 1 is a mildy elliptical
ultra-faint system with luminosity MV from the Sun and 24 kpc from the LMC. From spectroscopy of measure a velocity dispersion of 2.7±0.5 km s?1 and find tentative evidence for a radial
velocity gradient consistent with 3 km s?1
rotation. Hydrus 1?s velocity dispersion indicates
that the system is dark matter dominated, but its dynamical mass-to-light ratio
?20 is significantly smaller than typical for ultra-faint dwarfs at similar luminosity.
The kinematics and spatial position of Hydrus 1 make it a very plausible member
of the family of satellites brought into the Milky Way by the Magellanic Clouds.
While Hydrus 1?s proximity and well-measured kinematics make it a promising target
for dark matter annihilation searches, we find no evidence for significant gamma-ray
emission from Hydrus 1. The new dwarf is a metal-poor galaxy with a mean metallicity
[Fe/H]=?2.5 and [Fe/H] standard deviation of 0.4 dex, similar to other systems of
similar luminosity. Alpha-abundances of Hyi 1 members indicate that star-formation
was extended, lasting between 0.1 and 1 Gyr, with self-enrichment dominated by SN
Ia. The dwarf also hosts a highly carbon-enhanced extremely metal-poor star with