Skip to main content

A TIDALLY DISRUPTING DWARF SPHEROIDAL AROUND THE GALAXY NGC 253

Image: Spiral galaxy NGC 253  Credit: Robert Gendler/Jim Mistin

The modern paradigm of cold dark matter with a cosmological constant (ΛCDM) predicts that galaxies form hierarchically - growing through the gradual merging of many smaller galaxies.


A giant spiral like our Milky Way is expected to undergo a succession of dwarf galaxy accretion events which have different observational signatures, depending on their occurrence in the past, present, or future. Ancient accretion events can be detected through careful sifting of the chemodynamical phase-space of halo stars. Ongoing accretion is implied by the presence of satellite galaxies within the halo, and imminent accretion is marked by the existence of field dwarfs near to their future hosts.

Left: Amateur images of NGC 253 and its satellite NGC 253-dw2.
The field of view is of ~ 67 x 60 kpc. North is up and East is left.
The zoom-in on NGC 253-dw2 covers ~ 8 x 7 kpc.
Right: Subaru/Suprime-Cam image.
Credit: Romanowsky, Martinez-Delgago et. al 2016
Some researchers (Romanowsky, Martinez-Delgago et. al 2016) report the discovery of NGC 253-dw2, a dwarf spheroidal (dSph) galaxy candidate undergoing tidal disruption around a nearby spiral galaxy NGC 253 in the Sculptor group: the first such event identified beyond the Local Group. it is noteworthy that the dwarf was found using small-aperture amateur telescopes, and followed up with Suprime-Cam on the 8 m Subaru Telescope in order to resolve its brightest stars.

The morphological properties of NGC 253-dw2 mark it as distinct from normal dSphs and imply ongoing disruption at a projected distance of ~ 50 kpc from the main galaxy. Their observations support the hierarchical paradigm wherein massive galaxies continously accrete less massive ones, and provide a new case study for dSph infall and dissolution dynamics.

The paper (Romanowsky, Martinez-Delgago et. al 2016) is available online and is published in the MNRAS. >>
http://mnrasl.oxfordjournals.org/content/457/1/L103.full.pdf
http://arxiv.org/pdf/1512.03815v2.pdf

Labels

Etichette:

Comments

Post a Comment

Popular posts from this blog

ORBITAL PERIODS OF THE PLANETS

For orbital period generally we refer to the sidereal period, that is the temporal cycle that it takes an object to make a full orbit, relative to the stars. This is the orbital period in an inertial (non-rotating) frame of reference (365,25 days for the earth).
Post a Comment
Read more

THE HITCHCHIKER'S GUIDE TO THE LOCAL SUPERCLUSTER

Image: Virgo Supercluster. Credit: Andrew Z. Colvin The Virgo Supercluster is a region with a diameter of 33 megaparsecs (~1000 times larger the Milky Way's diameter) containing at least 100 galaxy groups and clusters.
Post a Comment
Read more

MILLISECOND PULSAR ORIGIN OF THE GALACTIC CENTER GEV EXCESS

Image: The Milky Way. Credit: Serge Brunier Using γ-ray data from the Fermi Large Area Telescope, various groups have identified a clear excess emission in the inner Galaxy, at energies around a few GeV. This excess attracted great attention, because it has properties typical for a dark matter annihilation signal.
Post a Comment
Read more