We study molecular outflows in a sample of 25 nearby (z<0.17, d<750 Mpc) ULIRG systems (38 individual nuclei) as part of the"Physics of ULIRGs with MUSE and ALMA"(PUMA) survey, using ~400 pc (0.1-1.0"beam FWHM) resolution ALMA CO(2-1) observations. We used a spectro-astrometry analysis to identify high-velocity (>300 km/s) molecular gas disconnected from the galaxy rotation, which we attribute to outflows. In 77% of the 26 nuclei with $\log L_{IR}/L_{\odot}>11.8$, we identifid molecular outflows with an average $v_{out}= 490$ km/s, outflow masses $1-35 \times 10^7$ $M_{\odot}$, mass outflow rates $\dot{M}_{out}=6-300$ $M_{\odot}$ yr$^{-1}$, mass-loading factors $\eta = \dot{M}_{out}/SFR = 0.1-1$, and an average outflow mass escape fraction of 45%. The majority of these outflows (18/20) are spatially resolved with radii of 0.2-0.9 kpc and have short dynamical times ($t_{dyn}=R_{out}/v_{out}$) in the range 0.5-2.8 Myr. The outflow detection rate is higher in nuclei dominated by starbursts (SBs, 14/15=93%) than in active galactic nuclei (AGN, 6/11=55%). Outflows perpendicular to the kinematic major axis are mainly found in interacting SBs. We also find that our sample does not follow the $\dot{M}_{out}$ versus AGN luminosity relation reported in previous works. In our analysis, we include a sample of nearby main-sequence galaxies (SFR = 0.3-17 $M_{\odot}$ yr$^{-1}$) with detected molecular outflows from the PHANGS-ALMA survey to increase the $L_{IR}$ dynamic range. Using these two samples, we find a correlation between the outflow velocity and the SFR, as traced by $L_{IR}$ ($v_{out} \propto SFR^{0.25\pm0.01})$, which is consistent with what was found for the atomic ionised and neutral phases. Using this correlation, and the relation between $M_{out}/R_{out}$ and $v_{out}$, we conclude that these outflows are likely momentum-driven.

/pdf/physics-of-ulirgs-with-muse-and-alma-puma-iv-no-tight-2m2foc0j.pdf

Physics of ULIRGs with MUSE and ALMA: PUMA IV. No tight relation between cold molecular outflow rates and AGN luminosities

We analyze JWST NIRSpec$+$MIRI/MRS observations of the infrared (IR) gas-phase molecular bands of the most enshrouded source (D1) within the interacting system and luminous IR galaxy II\,Zw\,096. We report the detection of rovibrational lines of H$_2$O $ (sim 5.3-7.2 mu m) and 12CO nu =1-0 (sim 4.45-4.95 mu m) in D1. The CO band shows the R- and P-branches in emission and the spectrum of the H$_2$O band shows the P-branch in emission and the R-branch in absorption. The H$_2$O R-branch in absorption unveils an IR-bright embedded compact source in D1 and the CO broad component features a highly turbulent environment. From both bands, we also identified extended intense star-forming (SF) activity associated with circumnuclear photodissociation regions (PDRs), consistent with the strong emission of the ionised 7.7 mu m polycyclic aromatic hydrocarbon band in this source. By including the 4.5-7.0 mu m continuum information derived from the H$_2$O and CO analysis, we modelled the IR emission of D1 with a dusty torus and SF component. The torus is very compact (diameter of sim 3\,pc at 5 mu m) and characterised by warm dust (sim 370\,K), giving an IR surface brightness of sim 3.6times 108\,L$_ This result suggests the presence of a dust-obscured active galactic nucleus (AGN) in D1, which has an exceptionally high covering factor that prevents the direct detection of AGN emission. Our results open a new way to investigate the physical conditions of inner dusty tori via modelling the observed IR molecular bands.

Structures Of Dust and gAs (SODA): Constraining the innermost dust properties of II Zw96 with JWST observations of H2O and CO

Abstract We present an analysis of the combined NIRSpec and MIRI spectra of dusty galaxies between 1.5 - 28 μm restframe by implementing a differential extinction model, where the strength of extinction varies across the spectrum as different layers of the obscuring dust are probed. Our model is able to recover a 2D distribution of dust temperature and extinction which allows inference of the physical nature of the dust in these environments. We show that differential extinction is necessary to reproduce the spectra of 4 highly obscured Luminous Infrared Galaxies observed with NIRSpec IFU and MIRI MRS, where simple screen or uniformly mixed dust distributions fail to fit the data. We additionally compare the extinction of H ii regions in these galaxies via hydrogen recombination lines, the extinction of molecular gas via the H2 lines, Polycyclic Aromatic Hydrocarbons via the 12.7/11.3 PAH ratio and the stellar continuum. We find that the molecular gas is deeply buried with the H ii regions in star-forming regions, with a similar extinction to the hottest dust components. However we find the cooler dust to be less obscured, at a similar extinction to the stellar continuum and PAHs. The nuclei show a complex dust distribution with VV114 NE, NGC 3256 S, IIZw96 SW showing a deeply buried continuum source relative to the molecular gas/H ii regions. Additionally, NGC 3256 S, NGC 7469 and VV114 SW show an isolated hot dust component, indicative of AGN heating, where NGC 3256 S and NGC 7469 are previously known AGN. 

pdf/peeling-back-the-layers-of-extinction-of-dusty-galaxies-in-3xbhqlv3wh.pdf

Peeling back the layers of extinction of dusty galaxies in the Era of JWST: Modelling joint NIRSpec + MIRI spectra at rest-frame 1.5–28 μm

Compact Obscured Nuclei (CONs) account for a significant fraction of the population of luminous and ultraluminous infrared galaxies (LIRGs and ULIRGs). These galaxy nuclei are compact, with radii of 10-100~pc, with large optical depths at submm and far-infrared wavelengths, and characterized by vibrationally excited HCN emission. It is not known what powers the large luminosities of the CON host galaxies because of the extreme optical depths towards their nuclei. CONs represent an extreme phase of nuclear growth, hiding either a rapidly accreting supermassive black hole or an abnormal mode of star formation. Here we apply principal component analysis (PCA) tomography to high-resolution (0.06$^{\prime\prime}$) ALMA observations at frequencies 245 to 265~GHz of the nearby CON (59~Mpc) IC~860. PCA is a technique to unveil correlation in the data parameter space, and we apply it to explore the morphological and chemical properties of species in our dataset. The leading principal components reveal morphological features in molecular emission that suggest a rotating, infalling disk or envelope, and an outflow analogous to those seen in Galactic protostars. One particular molecule of astrochemical interest is methanimine (CH$_2$NH), a precursor to glycine, three transitions of which have been detected towards IC 860. We estimate the average CH$_2$NH column density towards the nucleus of IC~860 to be $\sim10^{17}$cm$^{-2}$, with an abundance exceeding $10^{-8}$ relative to molecular hydrogen, using the rotation diagram method and non-LTE radiative transfer models. This CH$_2$NH abundance is consistent with those found in hot cores of molecular clouds in the Milky Way. Our analysis suggests that CONs are an important stage of chemical evolution in galaxies, that are chemically and morphologically similar to Milky Way hot cores.

/pdf/the-opaque-heart-of-the-galaxy-ic-860-analogous-protostellar-116bzqsi.pdf

The opaque heart of the galaxy IC 860: Analogous protostellar, kinematics, morphology, and chemistry

Context. Compact Obscured Nuclei (CONs) are an extreme phase of galaxy evolution where rapid supermassive black hole growth and / or compact star-forming activity is completely obscured by gas and dust. Aims. We investigate the properties of CONs in the mid-infrared and explore techniques aimed at identifying these objects such as through the equivalent width (EW) ratios of their Polycyclic Aromatic Hydrocarbon (PAH) features. Methods. We model Spitzer spectra by decomposing the continua into nuclear and star-forming components from which we then measure the nuclear optical depth, τ N , of the 9 . 8 µ m silicate absorption feature. We also use Spitzer spectral maps to investigate how PAH EW ratios vary with aperture size for objects hosting CONs. Results. We ﬁnd that the nuclear optical depth, τ N , strongly correlates with the HCN-vib emission line in the millimetre for CONs with a Pearson correlation coe ﬃ cient of 0.91. We ﬁnd the PAH EW ratios technique to be e ﬀ ective at selecting CONs and robust against highly inclined galaxies where strong dust lanes may mimic a CON like spectrum by producing a high τ N . Our analysis of the Spitzer spectral maps showed that the e ﬃ cacy of the PAH EW ratios to isolate CONs is reduced when there is a strong star-forming component from the host galaxy. In addition, we ﬁnd that the use of the inferred nuclear optical depth is a reliable method to identify CONs in 36 + 8 − 7 % of ULIRGs and 17 + 3 − 3 % of LIRGs, consistent with previous work. Conclusions. We conﬁrm mid-IR spectra to be a powerful diagnostic of CONs where the increased sensitivity of JWST will allow identiﬁcation of CONs at cosmic noon revealing this extreme but hidden phase of galaxy evolution.

A detailed look at the most obscured galactic nuclei in the mid-infrared

On unveiling buried nuclei with JWST: A technique for hunting the most obscured galaxy nuclei from local to high redshift

Compact obscured nuclei (CONs) are mainly found in local luminous and ultraluminous infrared galaxies (U / LIRGs). In the local Universe, these sources are generally selected through the detection of the HCN–vib (3-2) emission line at submillimetre wavelengths. In this work, we present a diagnostic method to select deeply buried nuclei based on mid-infrared (mid-IR) polycyclic aromatic hydrocarbons (PAHs) and mid-IR continuum ratios. Using Spitzer InfraRed Spectrograph (IRS) spectra of a representative sample of local ULIRGs ( z < 0 . 27), we examine their PAH and underlying continuum emission ratios. For deeply embedded sources, we ﬁnd that the 9.7 µ m silicate absorption band has a particularly pronounced e ﬀ ect on the 11.3 µ m PAH feature. The low ﬂux level in the nuclear silicate absorption band enhances the 11.3 µ m PAH feature contrast (high PAH equivalent width) compared to that of the other PAH features. The technique has been extended to include the use of the underlying 11.3 / 12.7 and 11.3 / 6.2 µ m continuum ratios. However, the latter are a ﬀ ected by the extinction coming from both the host galaxy and the nuclear region, whereas the foreground (host-galaxy) extinction is cancelled out when using the PAH equivalent width ratios. We apply our method to local U / LIRGs from the HERUS and GOALS samples and classify 14 ULIRGs and 10 LIRGs as CON candidates, which corresponds to 30% of the ULIRGs and 7% of the LIRGs from these samples. We ﬁnd that the observed continuum ratios of CON-dominated sources can be explained by assuming torus models with a tapered disc geometry and a smooth dust distribution. This suggests that the nuclear dusty structure of deeply obscured galaxy nuclei has an extremely high dust coverage. Finally, we demonstrate that the use of mid-IR colour–colour diagrams is an e ﬀ ective way to select CON-dominated sources at di ﬀ erent redshifts. In particular, the combination of ﬁlters of the James Webb Space Telescope / Mid-Infrared Instrument will enable the selection of CONs out to z ∼ 1 . 5. This will allow the selection of CONs to be extended to high redshifts where U / LIRGs are more numerous.

A technique to select the most obscured galaxy nuclei

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On unveiling buried nuclei with JWST: A technique for hunting the most obscured galaxy nuclei from local to high redshift

A technique to select the most obscured galaxy nuclei