Magneto-optical absorption coefficients in monolayer MoSe2

We study the linear, third-order nonlinear, and total absorption coefficients (OACs) caused by intra- and inter-band transitions in monolayer MoSe2 in the presence of a magnetic field by using the compact density matrix approach. The results show that the OACs display the blue-shift behaviour with an increase in the magnetic field. The Zeeman fields do not affect the peak positions but reduce peak intensities slightly. Besides, the strong spin-orbit coupling in monolayer MoSe2 causes the peaks to differ significantly due to spin-up and spin-down. The OACs due to intra-band transition display only one peak in the THz range, while the inter-band spectra show a series of peaks in the near-infrared optical range, making monolayer MoSe2 a promising candidate for novel optoelectronic applications

Medium Resolution Near-Infrared Spectra of the Host Galaxies of Nearby Quasars

We present medium resolution near-infrared host galaxy spectra of low redshift quasars, PG 0844 + 349 (z=0.064), PG 1226 + 023 (z=0.158), and PG 1426+015 (z=0.086). The observations were done by using the Infrared Camera and Spectrograph (IRCS) at the Subaru 8.2 m telescope. The full width at half maximum of the point spread function was about 0.3 arcsec by operations of an adaptive optics system, which can effectively resolve the quasar spectra from the host galaxy spectra. We spent up to several hours per target and developed data reduction methods to reduce the systematic noises of the telluric emissions and absorptions. From the obtained spectra, we identified absorption features of Mg I (1.503 um), Si I (1.589 um) and CO (6-3) (1.619 um), and measured the velocity dispersions of PG 0844 + 349 to be 132+/-110 km s-1 and PG 1426 + 015 to be 264+/-215 km s-1. By using an M_BH-sigma relation of elliptical galaxies, we derived the black hole (BH) mass of PG 0844+349, log(M_BH/M_SUN) = 7.7+/-5.5 and PG 1426+015, log(M_BH/M_SUN) = 9.0+/-7.5. These values are consistent with the BH mass values from broad emission lines with an assumption of a virial factor of 5.5.Comment: 16 pages, 5 figure

Calibrating Mg II-based black-hole mass estimators using Low-to-High-Luminosity Active Galactic Nuclei

We present single-epoch black-hole mass (\mbh) estimators based on the rest-frame ultraviolet (UV) \MgII\ 2798\AA\ and optical \Hb\ 4861\AA\ emission lines. To enlarge the luminosity range of active galactic nuclei (AGNs), we combine the 31 reverberation-mapped AGNs with relatively low luminosities from Bahk et al. 2019, 47 moderate-luminosity AGNs from Woo et al. 2018, and 425 high-luminosity AGNs from the Sloan Digital Sky Survey (SDSS). The combined sample has the monochromatic luminosity at 5100\AA\ ranging $\mathrm{\log \lambda L_{5100} \sim 41.3-46.5}$ \ergs, over the range of 5.5 $<$ $\log$\mbh\ $<$ 9.5. Based on the fiducial mass from the line dispersion or full width half maximum (FWHM) of \Hb\ paired with continuum luminosity at 5100\AA, we calibrate the best-fit parameters in the black hole mass estimators using the \MgII\ line. We find that the differences in the line profiles between \MgII\ and \Hb\ have significant effects on calibrating the UV \mbh\ estimators. By exploring the systematic discrepancy between the UV and optical \mbh\ estimators as a function of AGN properties, we suggest to add correction term $\Delta$M = -1.14 $\rm \log(FWHM_{MgII}/\sigma_{MgII}$) + 0.33 in the UV mass estimator equation. We also find a $\sim$0.1 dex bias in the \mbh\ estimation due to the difference of the spectral slope in the 2800-5200 \AA\ range. Depending on the selection of \mbh\ estimator based on either line dispersion or FWHM and either continuum or line luminosity, the derived UV mass estimators show >~0.1 dex intrinsic scatter with respect to the fiducial \Hb\ based \mbh.Comment: 19 pages, 15 figures, 3 tables. Accepted for publication in Ap

[OIII] 5007A Emission Line Width as a Surrogate for stellar dispersion in Type 1 AGNs?

We present a study of the relation between the [OIII] 5007A emission line width (sigma_{[OIII]}) and stellar velocity dispersion (sigma_{*}), utilizing a sample of 740 type 1 active galactic nuclei (AGNs) with high-quality spectra at redshift z < 1.0. We find the broad correlation between the core component of [OIII] emission line width (sigma_{[OIII,core]}) and sigma_{*} with a scatter of 0.11~dex for the low redshift (z < 0.1) sample; for redshift (0.3 < z < 1.0) AGNs, the scatter is larger, being 0.16~dex. We also find that the Eddington ratio (L_{bol}/L_{Edd}) may play an important role in the discrepancies between sigma_{[OIII,core]} and sigma_{*}. As the L_{bol}/L_{Edd} increases, sigma_{[OIII,core]} tends to be larger than sigma_{*}. By classifying our local sample with different minor-to-major axis ratios, we find that sigma_{*} is larger than sigma_{[OIII,core]} for those edge-on spiral galaxies. In addition, we also find that the effects of outflow strength properties such as maximum outflow velocity (V_{max}) and the broader component of [OIII] emission line width and line shift (sigma_{[OIII,out]} and V_{[OIII,out]}) may play a major role in the discrepancies between sigma_{[OIII,core]} and sigma_{*}. The discrepancies between sigma_{[OIII,core]} and sigma_{*} are larger when V_{max}, V_{[OIII,out]}, and sigma_{[OIII,out]} increase. Our results show that the outflow strengths may have significant effects on the differences between narrow-line region gas and stellar kinematics in AGNs. We suggest that caution should be taken when using sigma_{[OIII,core]} as a surrogate for sigma_{*}. In addition, the substitute of sigma_{[OIII,core]} for sigma_{*} could be used only for low luminosity AGNs.Comment: 17 pages, Accepted for publication in Ap

A preliminary study of photometric redshifts based on the Wide Field Survey Telescope

The Wide Field Survey Telescope (WFST) is a dedicated time-domain multi-band ($u$, $g$, $r$, $i$, and $z$) photometric survey facility under construction. In this paper, we present a preliminary study that assesses the quality of photometric redshifts based on WFST by utilizing mock observations derived with the galaxy catalog in the COSMOS/UltraVISTA field. We apply the template fitting technique to estimate photometric redshifts by using the ZEBRA photometric-redshift code and adopting a modified set of adaptive templates. We evaluate the bias (median relative offset between the output photometric redshifts and input redshifts), normalized median absolute deviation ($\sigma_{\rm NMAD}$) and outlier fraction ($f_{\rm outlier}$) of photometric redshifts in two typical WFST observational cases, the single 30-second exposure observations (hereafter shallow mode) and co-added 50-minute exposure observations (hereafter deep mode). We find bias\la0.006, \sigma_{\rm NMAD}\la0.03, and f_{\rm outlier}\la5\% in the shallow mode and bias$\approx 0.005$, $\sigma_{\rm NMAD}\approx 0.06$, and $f_{\rm outlier}\approx 17\%$--$27\%$ in the deep mode, respectively, under various lunar phases. Combining the WFST mock observational data with that from the upcoming CSST and Euclid surveys, we demonstrate that the $z_{\rm phot}$ results can be significantly improved, with $f_{\rm outlier}\approx 1\%$ and $\sigma_{\rm NMAD}\approx 0.02$.Comment: 20 pages, 13 figures. Accepted for publication in Research in Astronomy and Astrophysics (RAA