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Title: Unveiling kinematic structure in the starburst heart of NGC 253
ABSTRACT We observed the Brackett α emission line (4.05 μm) within the nuclear starburst of NGC 253 to measure the kinematics of ionized gas, and distinguish motions driven by star formation feedback from gravitational motions induced by the central mass structure. Using NIRSPEC on Keck II, we obtained 30 spectra through a $$0^{\prime \prime }_{.}5$$ slit stepped across the central ∼5 arcsec × 25 arcsec (85 × 425 pc) region to produce a spectral cube. The Br α emission resolves into four nuclear sources: S1 at the infrared core (IRC), N1 at the radio core, and the fainter sources N2 and N3 in the northeast. The line profile is characterized by a primary component with Δvprimary ∼90–130 $$\rm km\, s^{-1}$$ (full width at half-maximum) on top of a broad blue 2wing with Δvbroad ∼300–350 $$\rm km\, s^{-1}$$, and an additional redshifted narrow component in the west. The velocity field generated from our cube reveals several distinct patterns. A mean NE–SW velocity gradient of +10 $$\rm km\, s^{-1}$$ arcsec−1 along the major axis traces the solid-body rotation curve of the nuclear disc. At the radio core, isovelocity contours become S-shaped, indicating the presence of secondary nuclear bar of total extent ∼5 arcsec (90 pc). The symmetry of the bar places the galactic centre, and potential supermassive black hole, near the radio peak rather than the IRC. A third kinematic substructure is formed by blueshifted gas near the IRC. This feature likely traces a ∼100–250 $$\rm km\, s^{-1}$$ starburst-driven outflow, potentially linking the IRC to the galactic wind observed on kpc scales.  more » « less
Award ID(s):
2006433
PAR ID:
10282646
Author(s) / Creator(s):
; ;
Date Published:
Journal Name:
Monthly Notices of the Royal Astronomical Society
Volume:
493
Issue:
1
ISSN:
0035-8711
Page Range / eLocation ID:
627 to 637
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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