AGN-driven Cold Gas Outflow of NGC 1068 Characterized by Dissociation-sensitive Molecules

Abstract

Recent developments in (sub)millimeter facilities have drastically changed the amount of information obtained from extragalactic spectral scans. In this paper, we present a feature extraction technique using principal component analysis (PCA) applied to arcsecond-resolution (1.″0–2.″0 = 72–144 pc) spectral scan data sets for the nearby type-2 Seyfert galaxy NGC 1068, using Band 3 of the Atacama Large Millimeter/submillimeter Array. We apply PCA to 16 well-detected molecular line intensity maps convolved to a common 150 pc resolution. In addition, we include the [S iii]/[S ii] line ratio and [C i] 3 P 1–3 P 0 maps in the literature, both of whose distributions show a remarkable resemblance to that of a kiloparsec-scale biconical outflow from the central active galactic nucleus. We identify two prominent features: (1) central concentration at the circumnuclear disk (CND) and (2) two peaks across the center that coincide with the biconical outflow peaks. The concentrated molecular lines in the CND are mostly high-dipole molecules (e.g., H13CN, HC3N, and HCN). Line emissions from molecules known to be enhanced in an irradiated interstellar medium, CN, C2H, and HNC, show similar concentrations and extended components along the bicone, suggesting that molecule dissociation is a dominant chemical effect of the cold molecular outflow of this galaxy. Although further investigation should be made, this scenario is consistent with the faintness or absence of emission lines from CO isotopologues, CH3OH, and N2H+ in the outflow, which are easily destroyed by dissociating photons and electrons.

PHANGS–JWST First Results: Stellar-feedback-driven Excitation and Dissociation of Molecular Gas in the Starburst Ring of NGC 1365?

“…We observe 2). These line ratios and abundance ratio are much lower than those measured in the more powerful AGNs in NGC 7469 (Izumi et al 2020) and NGC 1068 (Saito et al 2022a(Saito et al , 2022b, which have…”

“…Thanks to high-resolution optical, e.g., LEGUS (Calzetti et al 2015), PHANGS-HST (Lee et al 2022), PHANGS-MUSE (Emsellem et al 2022), MAD (Erroz-Ferrer et al 2019), and TIMER (Gadotti et al 2019), and millimeter-wave imaging, e.g., NUGA (Combes et al 2019), PHANGS-ALMA (Leroy et al 2021a), and GATOS (García-Burillo et al 2021), we have made great strides in understanding the interplay of molecular gas, star formation, and stellar feedback in normal galaxy disks, e.g., feedback timescales (Grasha et al 2018;Kruijssen et al 2019;Chevance et al 2020;Kim et al 2022;Pan et al 2022), pressure and turbulence (Sun et al 2020;Barnes et al 2021Barnes et al , 2022, outflows of AGNs (Audibert et al 2019;García-Burillo et al 2021;Saito et al 2022aSaito et al , 2022b, to name a few. However, the nuclear starbursts, which contain a significant to dominant fraction of a host galaxy's star formation and especially the most massive (M å  10 6 M e ) YMCs, are still far from being well understood.…”

“…C I molecular outflows in AGN host galaxies (e.g.,Saito et al 2022aSaito et al , 2022b, with R CICO ∼ 1). This agrees withSchinnerer et al (2023), who find no evidence for the ionized outflow to…”

Molecular Abundance of the Circumnuclear Region Surrounding an Active Galactic Nucleus in NGC 1068 Based on an Imaging Line Survey in the 3 mm Band with ALMA

“…Observations of other molecules toward this galaxy are quite limited even in the 3 mm band. With the exception of papers reported by our group (Takano et al 2014;Tosaki et al 2017;Saito et al 2022aSaito et al , 2022b In Figure 3, the molecules showing a variety of spatial distributions are likely due to the difference in physical/ chemical properties between the CND and SBR. The strong emissions of H 13 CN, H 13 CO + , SiO, HC 3 N, CH 3 CN, SO, and 13 CN are concentrated in the CND, whereas weak emissions were observed in the SBR.…”

“…In this work, it is difficult to identify this effect because the samples are only at three positions, and these are too discrete. In a recent study, Saito et al (2022b) also discussed the effect on molecules using a principal component analysis.…”