The-10th-c-manga-workshop:abstracts

The 10th C-MaNGA workshop, Tsinghua, Dec 23-24, 2019

Abstract Submission

Provide the requested information if you are going to give a talk at the meeting. Please follow the same format as the example (keep the example on the top and don't delete it!).

Example

• Title: A summary of the MaNGA science projects at Tsinghua

Speaker: Cheng Li

Abstract: I will summarize the ongoing MaNGA projects at Tsinghua.

Please submit your abstract before Dec. 15, 2019.

Submitted Abstracts

• Title: Constraining inner density slopes with stellar kinematics

Speaker: Ran Li/Kai Zhu

Abstract: Recent progress in constraining the mass model of MaNGA galaxies with JAM.

• Title: The Impact of Merging on The Origin of Kinematically Misaligned and Counter-rotating Galaxies in MaNGA

Speaker: Songlin Li

Abstract: Galaxy mergers and interactions are expected to play a signicant role leading to offsets between gas and stellar motions in galaxies. Herein we crossmatch galaxies in MaNGA MPL-8 with the Dark Energy Spectroscopic Instrument (DESI) Legacy Surveys and identify 538 galaxies with merging/interacting features to investigate their position angle offsets (dPA) between gas and stellar rotation. We find that there is a much higher merging/interacting fraction in misaligned galaxies (30< dPA <150) than that in co-rotators (dPA < 30). This result corroborates that merging/interacting is one of the sources to produce misaligned galaxies and recent merging events can contribute to maximum 40% of such misalignment. Furthermore, the marginal merging/interacting fraction in star-forming (SF) counter-rotators (dPA >150) indicates the negligible role of merging in the origin of SF counter-rotators. In addition, the slightly smaller merging/interacting fraction in non star-forming (non-SF) counter-rotators (0.140) than that in non-SF misaligned galaxies (0.220) agrees with that counter-rotating is a stable state, where tidal features disappear. Finally, the ratio of co-rotators to counter-rotators in non-SF merging/interacting galaxies is about 8:1, much larger than the prediction from the isotropic merging (1:1), which supports the speculation that gas and stars prefer to be aligned during merging, as the orbital angular momentum transfers to gas and stellar spin.

• Title: Host Galaxy Properties of CL-AGNs]{Host Galaxy Properties of Changing-look AGN Revealed in the MaNGA Survey

Speaker: Xiaoling Yu

Abstract: Changing-look AGNs (CL-AGNs) are those AGN population whose broad Balmer emission lines appear or disappear within a few years. We use the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey to identify five CL-AGNs. The 2-D photometric and kinematic maps reveal common features as well as some unusual properties of CL-AGN hosts as compared to the AGN hosts in general. All MaNGA CL-AGNs reside in the star-forming main sequence with pseudo-bulges, similar to MaNGA non-CL-AGNs, and follow the $M_{BH}-\sigma_{*}$ relationship. The kinematic measurements indicate that they have similar distributions in the plane of angular momentum versus galaxy ellipticity. MaNGA CL-AGNs however show much higher (20%) fraction of counter-rotating features compared to that (2%) in general star-formation population. In addition, MaNGA CL-AGNs prefer face-on host galaxies with all axis ratio > 0.7. Although low statistical significance, these results suggest that host galaxies could play a role in the CL-AGN phenomena.

• Title: Wolf-Rayet galaxies in MaNGA: catalog properties and constraints on the Initial Mass Function

Speaker: Fu-Heng Liang

Abstract: Wolf-Rayet (WR) galaxies are a rare population of galaxies that host living high-mass stars during their WR phase (i.e. WR stars), and are thus expected to provide interesting constraints on the stellar Initial Mass Function, massive star formation, stellar evolution models, etc. Spatially resolved spectroscopy should in principle provide a more efficient way of identifying WR galaxies than single-fiber surveys of galactic centers such as SDSS, as WR stars should be more preferentially found in discs. We have performed a thorough search for WR galaxies in a two-step method featuring HII region finder and full spectrum fitting. The resulting WR catalog includes 267 WR regions of ~500pc (radius) sizes, distributed in 90 galaxies from MPL7. We find WR regions are exclusively found in galaxies that show bluest colors and highest star formation rates for their mass, as well as late-type dominated morphologies and lower-than-average Sersic indices. We estimate the stellar mass function of WR galaxies, and the mass-dependent detection rate. The detection rate of WR galaxies is typically ~2%, with weak dependence on stellar mass. This detection rate is about 40 times higher than previous studies with SDSS single fiber data, and a factor of 2 lower than the CALIFA-based WR catalog. We make comparisons with SDSS and CALIFA studies, and conclude that different detection rates of different studies can be explained mainly by three factors: spatial coverage, spectral signal-to-noise ratio, and redshift ranges of the parent sample. We have also studied the spatially resolved properties of the WR regions. We studied the radial distribution of WR regions, finding half of the WR regions are located in galactic discs and half in the centers. We have also investigated the effects of merging events on WR region numbers and blue bump strength. We have extensively studied the global mass-metallicity relation (MZR) of WR galaxies, as well as the MZR of WR regions. We find a lower metallicity at given surface mass density, when compared to the general population as well as to normal star-forming HII regions. Finally, we used Starburst99 model to predict properties of WR population with different IMF slopes and other variables. With the comparison between model predictions and our catalog data, we conclude that only a varying IMF with gas-phase metallicity (top-heavy at low metallicity) is able to explain the observed distribution of WR regions in the plane of EW(blue bump) versus EW(Hb).