arXiv subjects

Song-lin Li

Publications and source records attributed to Song-lin Li.

5 recordsLinked to original sources

arXiv2025

Optimal strategies for measuring gas-phase metallicities in intermediate-redshift non-AGN and AGN-host galaxies using future instrumentation

Resolved measurements of gas-phase metallicities in galaxies that both do and do not host active galactic nuclei (AGN) are crucial for understanding the role of AGN in regulating galaxy growth over cosmic time. Recent work at $z=0$ has demonstrated that a self-consistent comparison of metallicities in AGN-host and non-AGN galaxies can be conducted within a Bayesian framework given sufficient coverage of rest-frame optical emission lines. The next generation of adaptive optics-assisted optical and near-infrared integral field spectrographs promise to deliver the improved sensitivity and spatial resolution required conduct comparable measurements at intermediate redshift ($z\sim 1-3$), albeit with a restricted set of emission lines dictated by the various filter and grating combinations available. In this work, we explore optimal strategies for recovering the metallicities of both AGN-host and non-AGN galaxies given these constraints. We consider suites of emission lines that will be practical to obtain at different redshifts, and test a range of strategies to measure metallicity using just these lines, evaluating their performance by comparison to measurements using all the lines to which we have access in $z=0$ optical spectra. Our results facilitate straightforward estimates of exposure times required by future instruments to reach specified accuracy goals in a range of redshift windows using optimal sets of lines, enabling the development of efficient observing strategies for future surveys. This study can be extended to spatially resolved galaxies in order to design optimal strategies for measuring metallicity fluctuation maps in addition to the mean metallicities we consider here.

astro-ph.GA↗

arXiv2025

Kinematic misalignment as a driver of black hole activity in galaxies with external interactions

The process of Active Galactic Nuclei (AGN) fuelling relies on the transport of gas across several orders of magnitude in physical scale until the gas reaches the supermassive black hole at the centre of a galaxy. This work explores the role of kinematically misaligned gas in the fuelling of AGN in a sample of 4769 local galaxies from the MaNGA survey. We investigate for the first time the relative role of external interactions and the presence of kinematic misalignment as mechanisms to explain the observed increase in AGN fraction in galaxies with large stellar to gas kinematic misalignment ($>$45 degrees). Using a sample of galaxies with evidence of recent external interactions we find that there is a significantly higher fraction of AGN in those where a large stellar to gas kinematic misalignment is observed (20$^{+6}_{-4}\%$) compared with 6.2$^{+0.6}_{-0.5}\%$ in galaxies where no kinematic misalignment is observed. We determine that gas to stellar misalignment has an important role in the fraction of AGN observed, increasing the AGN fraction beyond the potential effect of external interactions. This result demonstrates the importance of misaligned structures to the fuelling of supermassive black holes.

astro-ph.GA↗

arXiv2024

Comparing metallicity correlations in nearby non-AGN and AGN-host galaxies

The gas-phase metallicity distribution within galaxies records critical information about galactic evolution. In this work we investigate how active galactic nuclei (AGN) influence this distribution by measuring the two-point correlation functions of gas-phase metallicity in 95 non-AGN and 37 AGN-host galaxies from the Calar Alto Legacy Integral Field spectroscopy Area integral field spectrographic survey. We measure metallicity using a novel Bayesian method that properly includes both stellar and AGN contributions to emission line fluxes and allows us to measure metallicities in both AGN-host and non-AGN galaxies in a single, consistent framework. We find that the two-point correlation functions of both AGN-host and non-AGN galaxies are well-fit by a simple injection-diffusion model, and that the correlation lengths $l_\mathrm{corr}$ we derive for the non-AGN galaxies are reasonably consistent with those obtained in earlier work. The AGN-host galaxies generally have smaller $l_\mathrm{corr}$ than non-AGN galaxies at fixed stellar mass, but similar $l_\mathrm{corr}$ at fixed star formation rate (SFR), suggesting that the primary effect of hosting an AGN in this sample is a reduction in SFR at fixed stellar mass, and that this in turn suppresses the correlation length. Our findings further indicate that, while both SFR and stellar mass are positively correlated with metallicity correlation length $l_\mathrm{corr}$, the former is more fundamental, implying that fluctuations in the metallicity distribution within galaxies are driven more by short-term responses to physical processes such as star formation that can change much faster than a Hubble time.

astro-ph.GA↗

arXiv2020

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

Galaxy mergers and interactions are expected to play a significant 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 311 merging galaxies that have reliable measurements of the $Δ$PA, the difference between the stellar and gas kinematic position angles to investigate the impacts of merging on gas-stellar rotation misalignments. We find that the merging fractions of misaligned galaxies (30$^\circ$ $\leqslant$ $Δ$PA $<$150$^\circ$) are higher than that of co-rotators ($Δ$PA $<$ 30$^\circ$) in both quiescent and star-forming galaxies. This result suggests that merging is one process to produce kinematic misalignments. The merging fraction of counter-rotators ($Δ$PA $\leqslant$ 150$^\circ$) is lower than that of misaligned galaxies in both quiescent and star-forming galaxies, while in the latter it is likely even lower than that of co-rotators. The orbital angular momentum transfer to the spins of stars and gas during merging and the tidal feature disappearance can lead to small merging fractions in counter-rotators. Numerous new stars that inherit angular momentum from gas after merging can further lower the merging fraction of star-forming counter-rotators.

astro-ph.GA↗

arXiv2018

An early-type galaxy with an inner star-forming disk

Early-type galaxies (ETGs) are composed of two distinct populations: high-mass and low-mass, which are likely to be built via gas-poor merging and gas-rich merging/accretion, respectively. However, it is difficult to directly associate low-mass ETGs with gas-rich processes, because currently they are gas poor with no signs of ongoing star formation. We report a discovery of an ETG (SDSS J142055.01+400715.7) with Mstellar=10^10 Msun that offers direct evidence for gas-rich merging as the origin of low-mass ETGs. The integrated properties of the galaxy are consistent with a typical low-mass ETG, but the outer and inner regions show distinct dispersion- and rotation-dominated kinematics, respectively. There are some tidal features surrounding the galaxy. These two facts suggest very recent galaxy merging. Furthermore, the inner disk harbors on-going star formation, indicating the merging to be gas rich. This type of galaxy is rare but it may be a demonstration of the role the transient phase of gas-rich merging plays in making a low-mass ETG.

astro-ph.GA↗