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arXiv · 1702.02464

SDSS IV MaNGA: Discovery of an $H_{\alpha}$ blob associated with a dry galaxy pair -- ejected gas or a `dark' galaxy candidate?

Lihwai Lin·Jing-Hua Lin·Chin-Hao Hsu·Hai Fu·Song Huang·Sebastián F. Sánchez·Stephen Gwyn·Joseph D. Gelfand·Edmond Cheung·Karen Masters·Sébastien Peirani·Wiphu Rujopakarn·David V. Stark·Francesco Belfiore·M. S. Bothwell·Kevin Bundy·Alex Hagen·Lei Hao·Shan Huang·David Law·Cheng Li·Chris Lintott·Roberto Maiolino·Alexandre Roman-Lopes·Wei-Hao Wang·Ting Xiao·Fangting Yuan·Dmitry Bizyaev·Elena Malanushenko·Niv Drory·J. G. Fernández-Trincado·Zach Pace·Kaike Pan·Daniel Thomas
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Abstract

We report the discovery of a mysterious giant $H_{\alpha}$ blob that is $\sim 8$ kpc away from the main MaNGA target 1-24145, one component of a dry galaxy merger, identified in the first-year SDSS-IV MaNGA data. The size of the $H_{\alpha}$ blob is $\sim$ 3-4 kpc in radius, and the $H_{\alpha}$ distribution is centrally concentrated. However, there is no optical continuum counterpart in deep broadband images reaching $\sim$26.9 mag arcsec$^{-2}$ in surface brightness. We estimate that the masses of ionized and cold gases are $3.3 \times 10^{5}$ $\rm M_{\odot}$ and $< 1.3 \times 10^{9}$ $\rm M_{\odot}$, respectively. The emission-line ratios indicate that the $H_{\alpha}$ blob is photoionized by a combination of massive young stars and AGN. Furthermore, the ionization line ratio decreases from MaNGA 1-24145 to the $H_{\alpha}$ blob, suggesting that the primary ionizing source may come from MaNGA 1-24145, likely a low-activity AGN. Possible explanations of this $H_{\alpha}$ blob include AGN outflow, the gas remnant being tidally or ram-pressure stripped from MaNGA 1-24145, or an extremely low surface brightness (LSB) galaxy. However, the stripping scenario is less favoured according to galaxy merger simulations and the morphology of the $H_{\alpha}$ blob. With the current data, we can not distinguish whether this $H_{\alpha}$ blob is ejected gas due to a past AGN outburst, or a special category of `ultra-diffuse galaxy' (UDG) interacting with MaNGA 1-24145 that further induces the gas inflow to fuel the AGN in MaNGA 1-24145.

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Lihwai Lin, Jing-Hua Lin, Chin-Hao Hsu, Hai Fu, Song Huang, Sebastián F. Sánchez, Stephen Gwyn, Joseph D. Gelfand, Edmond Cheung, Karen Masters, Sébastien Peirani, Wiphu Rujopakarn, David V. Stark, Francesco Belfiore, M. S. Bothwell, Kevin Bundy, Alex Hagen, Lei Hao, Shan Huang, David Law, Cheng Li, Chris Lintott, Roberto Maiolino, Alexandre Roman-Lopes, Wei-Hao Wang, Ting Xiao, Fangting Yuan, Dmitry Bizyaev, Elena Malanushenko, Niv Drory, J. G. Fernández-Trincado, Zach Pace, Kaike Pan, Daniel Thomas. 2017-02-08. SDSS IV MaNGA: Discovery of an $H_{\alpha}$ blob associated with a dry galaxy pair -- ejected gas or a `dark' galaxy candidate?. https://doi.org/10.3847/1538-4357/837/1/32

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