SDSS-IV MaNGA: the physical origin of off-galaxy H$\alpha$ blobs in the local Universe

Abstract

H$\alpha$ blobs are off-galaxy emission-line regions with weak or no optical counterparts. They are mostly visible in H$\alpha$ line, appearing as concentrated blobs. Such unusual objects have been rarely observed and studied, and their physical origin is still unclear. We have identified 13 H$\alpha$ blobs in the public data of MaNGA survey, by visually inspecting both the optical images and the spatially resolved maps of H$\alpha$ line for $\sim 4600$ galaxy systems. Among the 13 H$\alpha$ blobs, 2 were reported in previously MaNGA-based studies and 11 are newly discovered. This sample, though still small in size, is by far the largest sample with both deep imaging and integral field spectroscopy. Therefore, for the first time we are able to perform statistical studies to investigate the physical origin of H$\alpha$ blobs. We examine the physical properties of these H$\alpha$ blobs and their associated galaxies, including their morphology, environments, gas-phase metallicity, kinematics of ionized gas, and ionizing sources. We find that the H$\alpha$ blobs in our sample can be broadly divided into two groups. One is associated with interacting/merging galaxy systems, of which the ionization is dominated by shocks or diffuse ionized gas. It is likely that these H$\alpha$ blobs used to be part of their nearby galaxies, but were stripped away at some point due to tidal interactions. The other group is found in gas-rich systems, appearing as low-metallicity star-forming regions that are visually detached from the main galaxy. These H$\alpha$ blobs could be associated with faint disks, spiral arms, or dwarf galaxies.

26 pages, 18 figures, accepted for publication in MNRAS

References in corpus (25)

• The 2.5 m Telescope of the Sloan Digital Sky Survey
• The Host Galaxies and Classification of Active Galactic Nuclei
• Overview of the SDSS-IV MaNGA Survey: Mapping Nearby Galaxies at Apache Point Observatory
• Improving the full spectrum fitting method: accurate convolution with Gauss-Hermite functions
• Astrophysics Source Code Library
• Forty-Seven Milky Way-Sized, Extremely Diffuse Galaxies in the Coma Cluster
• Understanding Galaxy Evolution through Emission Lines
• The MaNGA Integral Field Unit Fiber Feed System for the Sloan 2.5 m Telescope
• The Data Reduction Pipeline for the SDSS-IV MaNGA IFU Galaxy Survey
• Tracing Galaxy Formation with Stellar Halos II: Relating Substructure in Phase- and Abundance-Space to Accretion Histories
• The SDSS-IV MaNGA Sample: Design, Optimization, and Usage Considerations
• SDSS-IV MaNGA IFS Galaxy Survey --- Survey Design, Execution, and Initial Data Quality
• SDSS-IV MaNGA: The Impact of Diffuse Ionized Gas on Emission-line Ratios, Interpretation of Diagnostic Diagrams, and Gas Metallicity Measurements
• Galaxy growth in the concordance $\Lambda$CDM cosmology
• The SAMI Galaxy Survey: Shocks and Outflows in a normal star-forming galaxy
• Blueberry galaxies: the lowest mass young starbursts
• Do galaxy global relationships emerge from local ones? The SDSS IV MaNGA surface mass density-metallicity relation
• HI-MaNGA: HI Followup for the MaNGA Survey
• The spatial extension of extended narrow line regions in MaNGA AGN
• Building a cluster: shocks, cavities, and cooling filaments in the group-group merger NGC 6338
• SDSS IV MaNGA: Discovery of an $H_{\alpha }$ blob associated with a dry galaxy pair -- ejected gas or a `dark' galaxy candidate?
• SDSS-IV MaNGA: A serendipitous observation of a potential gas accretion event
• Outlying H$\alpha$ emitters in SDSS IV MaNGA
• Evidence for Infalling Gas in a Lyman-$\alpha$ Blob
• SDSS-IV MaNGA: The Nature of an Off-galaxy H$\alpha$ Blob -- A Multi-wavelength View of Offset Cooling in a Merging Galaxy Group

Cited by in corpus (2)

• GA-NIFS and EIGER: A merging quasar host at z=7 with an overmassive black hole
• MaNGA 8313-1901: gas accretion observed in a blue compact dwarf galaxy?