Measurement of AGN dust extinction based on the near-infrared flux variability of WISE data

We present the measurement of the line-of-sight extinction of the dusty torus for a large number of obscured active galactic nuclei (AGNs) based on the reddening of the colour of the variable flux component in near-infrared (NIR) wavelengths. We collected long-term monitoring data by $\textit{Wide-field Infrared Survey Explorer (WISE)}$ for 513 local AGNs catalogued by the $\mathit{Swift/}$BAT AGN Spectroscopic Survey (BASS) and found that the multi-epoch NIR flux data in two different bands (WISE $W1$ and $W2$) are tightly correlated for more than 90% of the targets. The flux variation gradient (FVG) in the $W1$ and $W2$ bands was derived by applying linear regression analysis, and we reported that those for unobscured AGNs fall in a relatively narrow range, whereas those for obscured AGNs are distributed in a redder and broader range. The AGN's line-of-sight dust extinction ($A_V$) is calculated using the amount of the reddening in the FVG and is compared with the neutral hydrogen column density ($N_{\rm{}H}$) of the BASS catalogue. We found that the $N_{\rm{}H}/A_V$ ratios of obscured AGNs are greater than those of the Galactic diffuse interstellar medium (ISM) and are distributed with a large scatter by at most two orders of magnitude. Furthermore, we found that the lower envelope of the $N_{\rm{}H}/A_V$ of obscured AGNs is comparable to the Galactic diffuse ISM. These properties of the $N_{\rm{}H}/A_V$ can be explained by increase in the $N_{\rm{}H}$ attributed to the dust-free gas clouds covering the line of sight in the broad-line region.Comment: 11 pages, 7 figures, published in MNRA

Physical Characterization of Serendipitously Uncovered Millimeter-wave Line-emitting Galaxies at z∼2.5 behind the Local Luminous Infrared Galaxy VV 114

We thank the anonymous referee for a number of insightful comments and suggestions that greatly improved the quality of this paper. Data analysis was partly carried out on the common-use data analysis computer system at the Astronomy Data Center (ADC) of the National Astronomical Observatory of Japan (NAOJ). This paper makes use of the following ALMA data: ADS/JAO.ALMA#2013.1.01057.S, #2015.1.00973.S, #2015.1.00902.S, and #2013.1.00740.S. ALMA is a partnership of ESO (representing its member states), NSF (USA), and NINS (Japan), together with NRC (Canada), MOST and ASIAA (Taiwan), and KASI (Republic of Korea), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, AUI/NRAO and NAOJ. This work was supported by JSPS KAKENHI grant No. JP17H06130 and by the NAOJ ALMA Scientific Research grant No. 2017-06B. F.E. is supported by JSPS KAKENHI grant No. 17K14259. D.E. acknowledges support from a Beatriz Galindo senior fellowship (BG20/00224) from the Spanish Ministry of Science and Innovation. D. I. is supported by JSPS KAKENHI grant No. 321H01133.We present a detailed investigation of millimeter-wave line emitters ALMA J010748.3-173028 (ALMA-J0107a) and ALMA J010747.0-173010 (ALMA-J0107b), which were serendipitously uncovered in the background of the nearby galaxy VV 114 with spectral scan observations at lambda = 2-3 mm. Via Atacama Large Millimeter/submillimeter Array (ALMA) detection of CO(4-3), CO(3-2), and [C i](1-0) lines for both sources, their spectroscopic redshifts are unambiguously determined to be z = 2.4666 +/- 0.0002 and z = 2.3100 +/- 0.0002, respectively. We obtain the apparent molecular gas masses M-gas of these two line emitters from [C i] line fluxes as (11.2 +/- 3.1) x 10(10) M-circle dot and (4.2 +/- 1.2) x 10(10) M-circle dot, respectively. The observed CO(4-3) velocity field of ALMA-J0107a exhibits a clear velocity gradient across the CO disk, and we find that ALMA-J0107a is characterized by an inclined rotating disk with a significant turbulence, that is, a deprojected maximum rotation velocity to velocity dispersion ratio v(max)/sigma(v) of 1.3 +/- 0.3. We find that the dynamical mass of ALMA-J0107a within the CO-emitting disk computed from the derived kinetic parameters, (1.1 +/- 0.2) x 10(10) M-circle dot, is an order of magnitude smaller than the molecular gas mass derived from dust continuum emission, (3.2 +/- 1.6) x 10(11) M-circle dot. We suggest this source is magnified by a gravitational lens with a magnification of mu greater than or similar to 10, which is consistent with the measured offset from the empirical correlation between CO-line luminosity and width.Ministry of Education, Culture, Sports, Science and Technology, Japan (MEXT) Japan Society for the Promotion of Science Grants-in-Aid for Scientific Research (KAKENHI) JP17H06130 17K14259 21H01133NAOJ ALMA Scientific Research grant 2017-06BBeatriz Galindo senior fellowship from the Spanish Ministry of Science and Innovation BG20/0022

J0107a: A Barred Spiral Dusty Star-forming Galaxy at z = 2.467

Dusty star-forming galaxies (DSFGs) are among the most massive and active star-forming galaxies during the cosmic noon. Theoretical studies have proposed various formation mechanisms of DSFGs, including major merger-driven starbursts and secular star-forming disks. Here, we report J0107a, a bright (∼8 mJy at observed-frame 888 μ m) DSFG at z = 2.467 that appears to be a gas-rich massive disk and might be an extreme case of the secular disk scenario. J0107a has a stellar mass M _⋆ ∼ 5 × 10 ^11 M _⊙ , molecular gas mass M _mol ≳ 10 ^11 M _⊙ , and a star formation rate of ∼500 M _⊙ yr ^−1 . J0107a does not have a gas-rich companion. The rest-frame 1.28 μ m JWST NIRCam image of J0107a shows a grand-design spiral with a prominent stellar bar extending ∼15 kpc. The Atacama Large Millimeter/submillimeter Array Band 7 continuum map reveals that the dust emission originates from both the central starburst and the stellar bar. 3D disk modeling of the CO(4–3) emission line indicates a dynamically cold disk with rotation-to-dispersion ratio ${V}_{\max }/\sigma \sim 8$ . The results suggest a bright DSFG may have a nonmerger origin, and its vigorous star formation may be triggered by the bar and/or rapid gas inflow