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: JAM results of MaNGA MPL-7 galaxies

Speaker: Kai Zhu

Abstract: We have analyzed 4706 MPL-7 galaxies with JAM. By comparing the results with those of MPL-5 galaxies, we find that JAM may be more sensitive to the Vrms(root-mean-square velocity) map than we thought.

• 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).

• Title: spatially resolved molecular gas and dust

Speaker: Niu Li

Abstract: we use a small sample (9 galaxies) from EDGE-CALIFA survey to study the spatial resolved molecular gas and dust. EDGE provides good quality CO data. The 9 galaxies also have Herschel (FIR) data which can be used to estimate dust mass by SED fitting. Our preliminary results show that the dust to gas ratio (DGR) is related to Ha surface density.

• Title: Kinematic Asymmetry as An Indicator of Galaxy Interaction in Paired Galaxies

Speaker: Shuai Feng

Abstract: The interaction between galaxies is believed to be the main origin of the peculiarities of galaxies, which disturbs not only the morphology but also their kinematics. These disturbed and asymmetric features are the indicators of galaxy interaction. We study the velocity field of the ionized gas of the paired galaxies in the SDSS-IV MaNGA IFU survey. Using the kinemetry package, we fit the velocity field of the ionized gas to quantify the degree of kinematic asymmetry. We find that the star formation rate (SFR) of the paired galaxies with high kinematic asymmetry is significantly enhanced even when the projected separation between the pair members is quite large (dp∼100kpc). On the contrary, no significant SFR enhancement is found for the paired galaxies with low kinematic asymmetry even when their projected separation is small (dp<30kpc). Moreover, we also find that the fraction of galaxies with high kinematic asymmetry is much higher in close pairs (dp<30kpc) than those with larger dp, which explains well the early statistical finding of the significant SFR enhancement in close pairs. Our new findings illustrate that the kinematic asymmetry is an excellent indicator of galaxy-galaxy interaction strength, which helps us better understand the merging phase of the observed galaxy pairs.

• Title: Asymmetries in disk galaxies and its implication for dust attenuation and galaxy orientation

Speaker: Fang-Ting Yuan

Abstract: We calculated the asymmetry parameter for a sample of MaNGA galaxies. We show that the asymmetries of the ha images and color images are consistent with our dust models. We also show how asymmetry can be used to help decipher the near or far side of galaxies.

• Title: The relations between Vrms radial profile and other galaxy properties

Speaker: Shengdong Lu

Abstract: We calculated the radial profiles of vrms (root-mean-square velocity) of a sample of MaNGA galaxies. We find that the radial slope of the vrms profile is a good trace of the bulge-to-total ratio of galaxies. It shows a strong relation with the inner density slope of galaxies, which provides an economical way to estimate the density slope of galaxies. The slope of vrms radial profile is found to correlate with age and metallicity, which is, however, actually from the relation between vrms and stellar population properties. It shows the remarkable extent to which galaxies can be described by a one-parameter family driven by sigma_e.

• Title: Gas accretion of blue compact galaxy?

Speaker: Mengting Ju

Abstract: In the SDSS-IV survey (MaNGA), we found that a peculiar BCD, MaNGA 8313-1901, at \textit{z} = 0.02425 with a big blue off-center clump in north-east from the SDSS image. may be undergoing a process of gas accretion, which is confirmed by DAP data.

• Title: Bayesian analysis of the star formation history of low-mass galaxies in MaNGA

Speaker: Shuang Zhou

Abstract: As the smallest, least luminous, however most common systems in the universe, dwarf galaxies have come to play an increasingly important role in understanding how galaxies form and evolve. We use a Bayesian inference code to analyze the IFU data-cubes of low mass galaxies in MaNGA, aiming to examine the star formation history of those galaxies. We calculate Bayesian evidence ratios for two SFH models and find that there is generally an old stellar population hidden behind the bright young populations in low mass galaxies. We show how the assumed SFH model can bias the inference of the SFHs, and find environmental effects on the SFH. With the help of UKIDSS NIR photometry, we further constrain the mass fractions contained in the old population. We discuss the radial dependence of the SFH characterized by the half mass formation times and cumulative SFHs, and compare those results with previous studies.

• Title: Post-starburst galaxies in MaNGA

Speaker: Yanmei Chen

Abstract: Introduce our work about MaNGA post-starburst galaxies and some following plan.