University of Oulu

H. Salo and E. Laurikainen 2017 ApJ 835 252

Boxy/Peanut/X-shaped bulges : steep inner rotation curve leads to barlens face-on morphology

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Author: Salo, H.1; Laurikainen, E.1
Organizations: 1Astronomy Research Unit, University of Oulu, FI-90014 Finland
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 2.1 MB)
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Language: English
Published: IOP Publishing, 2017
Publish Date: 2017-12-20


We use stellar dynamical bulge / disk / halo simulations to study whether barlenses (lens-like structures embedded in the narrow bar component) are only the face-on counterparts of Boxy / Peanut / X-shapes (B / P / X) seen in edge-on bars, or if some additional physical parameter affects that morphology. A range of bulge-to-disk mass and size ratios are explored: our nominal parameters (B / D = 0.08, reff / hr = 0.07, disk comprising two-thirds of total force at 2.2hr) correspond to typical Milky Way mass galaxies. In all models, a bar with pronounced B/P/X forms in a few Gyr, visible in the edge-on view. However, the pure barlens morphology forms only in models with sufficiently steep inner rotation curves, dVcir / dr ≳ 5Vmax / hr, achieved when including a small classical bulge with B / D ≳ 0.02 and reff / hr ≲ 0.1. For shallower slopes, the central structure still resembles a barlens, but shows a clear X signature even in low inclinations. A similar result holds for bulge-less simulations, where the central slope is modified by changing the halo concentration. The predicted sensitivity on the inner rotation curve is consistent with the slopes that are estimated from gravitational potentials calculated from the 3.6 μm images, for the observed barlens and X-shaped galaxies in the Spitzer Survey of Stellar Structure in Galaxies (S⁴G). For inclinations <60° the galaxies with barlenses have on average twice steeper inner rotation curves than galaxies with X shapes: the limiting slope is ~ 250 km s⁻¹ kpc⁻¹. Among barred galaxies, those with barlenses have both the strongest bars and the largest relative excess of inner surface density, both in barlens regions (≲0.5hr) and near the center (≲0.1hr); this provides evidence for bar-driven secular evolution in galaxies.

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Series: Astrophysical journal
ISSN: 0004-637X
ISSN-E: 1538-4357
ISSN-L: 0004-637X
Volume: 835
Issue: 2
Article number: 252
DOI: 10.3847/1538-4357/835/2/252
Type of Publication: A1 Journal article – refereed
Field of Science: 115 Astronomy and space science
Funding: This work was supported by the DAGAL network: People Programme (Marie Curie Actions) of the European Unions Seventh Framework Programme FP7/2007-2013 under REA grant agreement number PITN-GA-2011-289313. The grant from Academy of Finland (No. 297738) is also acknowledged.
EU Grant Number: (289313) DAGAL - Detailed Anatomy of Galaxies
Academy of Finland Grant Number: 297738
Detailed Information: 297738 (Academy of Finland Funding decision)
Copyright information: © 2017. The American Astronomical Society. All rights reserved. Published in this repository with the kind permission of the publisher.