The nucleus of NGC 253 and its massive stellar clusters at parsec scales

Abstract

Very Large Telescope adaptive optics images of NGC 253 with resolutions down to 200 mas resolve the central 300 pc of this galaxy in ~ 37 infrared (IR) bright knots, a factor of 3 larger than previously reported, and extended diffuse emission. The angular resolution, comparable to that of available Very Large Array 2 cm maps, permits us a very accurate IR-radio registration. Eight radio sources are found to have an IR counterpart. The knots have Hαequivalent width of about 80 angstroms, sizes of ~ 3 pc, magnitudes in L-band of about 12 mag and relatively high extinction, Av ~ 7 mag. Their spectral energy distributions (SEDs) look very similar, characterized by a maximum at 20 micron and a gentle bump in the 1 - 2 micron range. These features can be well reproduced by considering an important contribution of very young stellar objects to the IR, efficiently heating their dust envelope. The evidence indicates that these are young massive clusters bursting from their dust cocoons. A median SED of the knots is provided, which may represent one of the most genuine templates of an extragalactic circumnuclear star-forming region. The lack of any optical or IR counterpart for the previously identified radio core calls into question its supposed active nucleus nature. This source may instead represent a scaled up version of Sgr A* at the Galactic Centre.

5 pages, 3 figures. Accepted for publication in MNRAS (Letters)

References in corpus (3)

• A New View of the Super Star Clusters in the Low-Metallicity Galaxy SBS 0335-052
• The Sub-parsec Scale Radio Properties of Southern Starburst Galaxies. I. Supernova Remnants, the Supernova Rate, and the Ionised Medium in the NGC 253 Starburst
• VLA H53alpha and H92alpha line observations of the central region of NGC 253

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