Naval Research Laboratory Remote Sensing Division

We study the properties of massive, galactic-scale outflows of molecular gas and investigate their impact on galaxy evolution. We present new IRAM PdBI CO(1–0) observations of local ultra-luminous infrared galaxies (ULIRGs) and quasar-hosts: a clear signature of massive and energetic molecular outflows, extending on kpc scales, is found in the CO(1–0) kinematics of four out of seven sources, with measured outflow rates of several 100 M⊙ yr-1. We combine these new observations with data from the literature, and explore the nature and origin of massive molecular outflows within an extended sample of 19 local galaxies. We find that starburst-dominated galaxies have an outflow rate comparable to their star formation rate (SFR), or even higher by a factor of ~2–4, implying that starbursts can indeed be effective in removing cold gas from galaxies. Nevertheless, our results suggest that the presence of an active galactic nucleus (AGN) can boost the outflow rate by a large factor, which is found to increase with the LAGN/Lbol ratio. The gas depletion time scales due to molecular outflows are anti-correlated with the presence and luminosity of an AGN in these galaxies, and range from a few hundred million years in starburst galaxies down to just a few million years in galaxies hosting powerful AGNs. In quasar hosts, the depletion time scales due to the outflow are much shorter than the depletion time scales due to star formation. We estimate the outflow kinetic power and find that, for galaxies hosting powerful AGNs, it corresponds to about 5% of the AGN luminosity, as expected by models of AGN feedback. Moreover, we find that momentum rates of about 20 LAGN/c are common among the AGN-dominated sources in our sample. For “pure” starburst galaxies, our data tentatively support models in which outflows are mostly momentum-driven by the radiation pressure from young stars onto dusty clouds. Overall, our results indicate that, although starbursts are effective in powering massive molecular outflows, the presence of an AGN may strongly enhance such outflows, and therefore have a profound feedback effect on the evolution of galaxies by efficiently removing fuel for star formation, hence quenching star formation.

Photodissociation region (PDR) models are computed over a wide range of physical conditions, from those appropriate to giant molecular clouds illuminated by the interstellar radiation field to the conditions experienced by circumstellar disks very close to hot massive stars. These models use the most up-to-date values of atomic and molecular data, the most current chemical rate coefficients, and the newest grain photoelectric heating rates, which include treatments of small grains and large molecules. In addition, we examine the effects of metallicity and cloud extinction on the predicted line intensities. Results are presented for PDR models with densities over the range n = 10 1 -10 7 cm -3 and for incident far-ultraviolet radiation fields over the range G 0 = 10 -0.5 -10 6.5 (where G 0 is the far-ultravioliet [FUV] flux in units of the local interstellar value), for metallicities Z = 1 and 0.1 times the local Galactic value, and for a range of PDR cloud sizes. We present line strength and/or line ratio plots for a variety of useful PDR diagnostics: [C II] 158 μm, [O I] 63 μm and 145 μm, [C I] 370 μm and 609 μm, CO J = 1-0, J = 2-1, J = 3-2, J = 6-5, and J = 15-14, as well as the strength of the far-infrared continuum. These plots will be useful for the interpretation of Galactic and extragalactic far-infrared and submillimeter spectra observable with the Infrared Space Observatory ( ISO ), the Stratospheric Observatory for Infrared Astronomy, the Submillimeter Wave Astronomy Satellite , the Far Infrared and Submillimeter Telescope , and other orbital and suborbital platforms. As examples, we apply our results to ISO and ground-based observations of M82, NGC 278, and the Large Magellanic Cloud. Our comparison of the conditions in M82 and NGC 278 show that both the gas density and FUV flux are enhanced in the starburst nucleus of M82 compared with those in the normal spiral NGC 278. We model the high [C II]/CO ratio observed in the 30 Doradus region of the LMC and find that it can be explained either by lowering the average extinction through molecular clouds or by enhancing the density contrast between the atomic layers of PDRs and the CO-emitting cloud cores. The ratio L [CO]/ M [H 2 ] implied by the low extinction model gives cloud masses too high for gravitational stability. We therefore rule out low-extinction clouds as an explanation for the high [C II]/CO ratio and instead appeal to density contrast in A V = 10 clouds.

The Very Large Array Sky Survey (VLASS) is a synoptic, all-sky radio sky survey with a unique combination of high angular resolution (≈2."5), sensitivity (a 1σ goal of 70 μJy/beam in the coadded data), full linear Stokes polarimetry, time domain coverage, and wide bandwidth (2–4 GHz). The first observations began in 2017 September, and observing for the survey will finish in 2024. VLASS will use approximately 5500 hr of time on the Karl G. Jansky Very Large Array (VLA) to cover the whole sky visible to the VLA (decl. > −40°), a total of 33 885 deg². The data will be taken in three epochs to allow the discovery of variable and transient radio sources. The survey is designed to engage radio astronomy experts, multi-wavelength astronomers, and citizen scientists alike. By utilizing an "on the fly" interferometry mode, the observing overheads are much reduced compared to a conventional pointed survey. In this paper, we present the science case and observational strategy for the survey, and also results from early survey observations.

Mass outflows driven by stars and active galactic nuclei (AGNs) are a key element in many current models of galaxy evolution. They may produce the observed black-hole–galaxy mass relation and regulate and quench both star formation in the host galaxy and black hole accretion. However, observational evidence of such feedback processes through outflows of the bulk of the star-forming molecular gas is still scarce. Here we report the detection of massive molecular outflows, traced by the hydroxyl molecule (OH), in far-infrared spectra of ULIRGs obtained with Herschel -PACS as part of the SHINING key project. In some of these objects the (terminal) outflow velocities exceed 1000 km s −1 , and their outflow rates (up to ∼1200 M ☉ yr −1 ) are several times larger than their star formation rates. We compare the outflow signatures in different types of ULIRGs and in starburst galaxies to address the issue of the energy source (AGN or starburst) of these outflows. We report preliminary evidence that ULIRGs with a higher AGN luminosity (and higher AGN contribution to L IR ) have higher terminal velocities and shorter gas depletion timescales. The outflows in the observed ULIRGs are able to expel the cold gas reservoirs from the centers of these objects within ∼10 6 –10 8 years.

We study the properties of massive, galactic-scale outflows of molecular gas and investigate their impact on galaxy evolution. We present new IRAM PdBI CO(1-0) observations of local ULIRGs and QSO hosts: clear signature of massive and energetic molecular outflows, extending on kpc scales, is found in the CO(1-0) kinematics of four out of seven sources, with measured outflow rates of several 100 M yr−1. We combine these new observations with data from the literature, and explore the nature and origin of massive molecular outflows within an extended sample of 19 local galaxies. We find that starburst-dominated galaxies have an outflow rate comparable to their SFR, or even higher by a factor of ∼2-4, implying that starbursts can indeed be effective in removing cold gas

We report the results from a systematic search for molecular (OH 119 μm) outflows with Herschel /PACS in a sample of 43 nearby ( z < 0.3) galaxy mergers, mostly ultraluminous infrared galaxies (ULIRGs) and QSOs. We find that the character of the OH feature (strength of the absorption relative to the emission) correlates with that of the 9.7 μm silicate feature, a measure of obscuration in ULIRGs. Unambiguous evidence for molecular outflows, based on the detection of OH absorption profiles with median velocities more blueshifted than −50 km s −1 , is seen in 26 (70%) of the 37 OH-detected targets, suggesting a wide-angle (∼145°) outflow geometry. Conversely, unambiguous evidence for molecular inflows, based on the detection of OH absorption profiles with median velocities more redshifted than +50 km s −1 , is seen in only four objects, suggesting a planar or filamentary geometry for the inflowing gas. Terminal outflow velocities of ∼−1000 km s −1 are measured in several objects, but median outflow velocities are typically ∼−200 km s −1 . While the outflow velocities show no statistically significant dependence on the star formation rate, they are distinctly more blueshifted among systems with large active galactic nucleus (AGN) fractions and luminosities [log ( L AGN / L ☉ ) ⩾ 11.8 ± 0.3]. The quasars in these systems play a dominant role in driving the molecular outflows. However, the most AGN dominated systems, where OH is seen purely in emission, show relatively modest OH line widths, despite their large AGN luminosities, perhaps indicating that molecular outflows subside once the quasar has cleared a path through the obscuring material.

We present a full high resolution SPIRE FTS spectrum of the nearby ultraluminous infrared galaxy Mrk 231. In total 25 lines are detected, including CO J = 5–4 through J = 13–12, 7 rotational lines of H2O, 3 of OH+ and one line each of H2O+, CH+, and HF. We find that the excitation of the CO rotational levels up to J = 8 can be accounted for by UV radiation from star formation. However, the approximately flat luminosity distribution of the CO lines over the rotational ladder above J = 8 requires the presence of a separate source of excitation for the highest CO lines. We explore X-ray heating by the accreting supermassive black hole in Mrk 231 as a source of excitation for these lines, and find that it can reproduce the observed luminosities. We also consider a model with dense gas in a strong UV radiation field to produce the highest CO lines, but find that this model strongly overpredicts the hot dust mass in Mrk 231. Our favoured model consists of a star forming disk of radius 560 pc, containing clumps of dense gas exposed to strong UV radiation, dominating the emission of CO lines up to J = 8. X-rays from the accreting supermassive black hole in Mrk 231 dominate the excitation and chemistry of the inner disk out to a radius of 160 pc, consistent with the X-ray power of the AGN in Mrk 231. The extraordinary luminosity of the OH+ and H2O+ lines reveals the signature of X-ray driven excitation and chemistry in this region.

In this first paper on the results of our Herschel PACS survey of local ultra luminous infrared galaxies (ULIRGs), as part of our SHINING survey of local galaxies, we present far-infrared spectroscopy of Mrk 231, the most luminous of the local ULIRGs, and a type 1 broad absorption line AGN. For the first time in a ULIRG, all observed far-infrared fine-structure lines in the PACS range were detected and all were found to be deficient relative to the far infrared luminosity by 1–2 orders of magnitude compared with lower luminosity galaxies. The deficits are similar to those for the mid-infrared lines, with the most deficient lines showing high ionization potentials. Aged starbursts may account for part of the deficits, but partial covering of the highest excitation AGN powered regions may explain the remaining line deficits. A massive molecular outflow, discovered in OH and 18OH, showing outflow velocities out to at least 1400 km s-1, is a unique signature of the clearing out of the molecular disk that formed by dissipative collapse during the merger. The outflow is characterized by extremely high ratios of 18O/16O suggestive of interstellar medium processing by advanced starbursts.

Abstract We present the fundamental properties of 87 stars based on angular diameter measurements from the Navy Precision Optical Interferometer, 36 of which have not been measured previously using interferometry. Our sample consists of 5 dwarfs, 3 subgiants, 69 giants, 3 bright giants, and 7 supergiants, and span a wide range of spectral classes from B to M. We combined our angular diameters with photometric and distance information from the literature to determine each star’s physical radius, effective temperature, bolometric flux, luminosity, mass, and age.

We present the SFI++ data set, a homogeneously derived catalog of photometric and rotational properties and the Tully-Fisher distances and peculiar velocities derived from them. We make use of digital optical images, optical long-slit spectra, and global H I line profiles to extract parameters of relevance to disk scaling relations, incorporating several previously published data sets as well as a new photometric sample of some 2000 objects. According to the completeness of available redshift samples over the sky area, we exploit both a modified percolation algorithm and the Voronoi-Delaunay method to assign individual galaxies to groups as well as clusters, thereby reducing scatter introduced by local orbital motions. We also provide corrections to the peculiar velocities for both homogeneous and inhomogeneous Malmquist bias, making use of the 2MASS Redshift Survey density field to approximate large-scale structure. We summarize the sample selection criteria, corrections made to raw observational parameters, the grouping techniques, and our procedure for deriving peculiar velocities. The final SFI++ peculiar velocity catalog of 4861 field and cluster galaxies is large enough to permit the study not just of the global statistics of large-scale flows but also of the details of the local velocity field.

We present a study of the [C II] 157.74 μm fine-structure line in a sample of 15 ultraluminous infrared (IR) galaxies (IR luminosity L IR ⩾ 10 12 L ☉ ; ULIRGs) using the Long Wavelength Spectrometer (LWS) on the Infrared Space Observatory ( ISO ). We confirm the observed order of magnitude deficit (compared to normal and starburst galaxies) in the strength of the [C II] line relative to the far-infrared (FIR) dust continuum emission found in our initial report, but here with a sample that is twice as large. This result suggests that the deficit is a general phenomenon affecting 4 out of 5 ULIRGs. We present an analysis using observations of generally acknowledged photodissociation region (PDR) tracers ([C II], [O I] 63 and 145 μm, and FIR continuum emission), which suggests that a high ultraviolet flux G 0 incident on a moderate density n PDR could explain the deficit. However, comparisons with other ULIRG observations, including CO (1-0), [C I] (1-0), and 6.2 μm polycyclic aromatic hydrocarbon (PAH) emission, suggest that high G 0 / n PDRs alone cannot produce a self-consistent solution that is compatible with all of the observations. We propose that non-PDR contributions to the FIR continuum can explain the apparent [C II] deficiency. Here, unusually high G 0 and/or n physical conditions in ULIRGs as compared to those in normal and starburst galaxies are not required to explain the [C II] deficit. Dust-bounded photoionization regions, which generate much of the FIR emission but do not contribute significant [C II] emission, offer one possible physical origin for this additional non-PDR component. Such environments may also contribute to the observed suppression of FIR fine-structure emission from ionized gas and PAHs, as well as the warmer FIR colors found in ULIRGs. The implications for observations at higher redshifts are also revisited.

We report the results from a systematic search for molecular (OH-119 um) outflows with Herschel-PACS in a sample of 43 nearby (z < 0.3) galaxy mergers, mostly ultraluminous infrared galaxies (ULIRGs) and QSOs. We find that the character of the OH feature (strength of the absorption relative to the emission) correlates with that of the 9.7-um silicate feature, a measure of obscuration in ULIRGs. Unambiguous evidence for molecular outflows, based on the detection of OH absorption profiles with median velocities more blueshifted than -50 km/sec, is seen in 26 (70%) of the 37 OH-detected targets, suggesting a wide-angle (~145 degrees) outflow geometry. Conversely, unambiguous evidence for molecular inflows, based on the detection of OH absorption profiles with median velocities more redshifted than +50 km/sec, is seen in only 4 objects, suggesting a planar or filamentary geometry for the inflowing gas. Terminal outflow velocities of ~-1000 km/sec are measured in several objects, but median outflow velocities are typically ~-200 km s^{-1}. While the outflow velocities show no statistically significant dependence on the star formation rate, they are distinctly more blueshifted among systems with large AGN fractions and luminosities [log (L_AGN / L_sun) > 11.8 +/- 0.3]. The quasars in these systems play a dominant role in driving the molecular outflows. In contrast, the most AGN dominated systems, where OH is seen purely in emission, show relatively modest OH line widths, despite their large AGN luminosities, perhaps indicating that molecular outflows subside once the quasar has cleared a path through the obscuring material.

We report initial results from the far-infrared fine structure line observations of a sample of 44 local starbursts, Seyfert galaxies, and infrared luminous galaxies obtained with the PACS spectrometer on board Herschel . We show that the ratio between the far-infrared luminosity and the molecular gas mass, , is a much better proxy for the relative brightness of the far-infrared lines than L FIR alone. Galaxies with high ratios tend to have weaker fine structure lines relative to their far-infrared continuum than galaxies with . A deficit of the [C ii ] 158 μm line relative to L FIR was previously found with the Infrared Space Observatory , but now we show for the first time that this is a general aspect of all far-infrared fine structure lines, regardless of their origin in the ionized or neutral phase of the interstellar medium. The value where these line deficits start to manifest is similar to the limit that separates between the two modes of star formation recently found in galaxies on the basis of studies of their gas–star formation relations. Our finding that the properties of the interstellar medium are also significantly different in these regimes provides independent support for the different star-forming relations in normal disk galaxies and major merger systems. We use the spectral synthesis code Cloudy to model the emission of the lines. The expected increase of the ionization parameter with can simultaneously explain the line deficits in the [C ii ], [N ii ], and [O i ] lines.

The Advanced Camera for Surveys and the Near Infrared Camera and Multi-Object Spectrometer (NICMOS) have been used to obtain new Hubble Space Telescope images of NGC 4038/4039 ("The Antennae"). These new observations allow us to better differentiate compact star clusters from individual stars, based on both size and color. We use this ability to extend the cluster luminosity function (LF) by approximately 2 mag over our previous WFPC2 results, and find that it continues as a single power law, dN / dL ∝ L α with α = −2.13 ± 0.07, down to the observational limit of M V ≈ −7. Similarly, the mass function (MF) is a single power law dN / dM ∝ M β with β = −2.10 ± 0.20 for clusters with ages <3 × 10 8 yr, corresponding to lower mass limits that range from 10 4 to 10 5 M ☉ , depending on the age range of the subsample. Hence, the power-law indices for the luminosity and MFs are essentially the same. The LF for intermediate-age clusters (i.e., ∼100–300 Myr old objects found in the loops, tails, and outer areas) shows no bend or turnover down to M V ≈ −6, consistent with relaxation-driven cluster disruption models which predict the turnover should not be observed until M V ≈ −4. An analysis of individual ∼0.5 kpc sized areas over diverse environments shows good agreement between values of α and β, similar to the results for the total population of clusters in the system. There is tentative evidence that the values of both α and β are flatter for the youngest clusters in some areas, but it is possible that this is caused by observational biases. Several of the areas studied show evidence for age gradients, with somewhat older clusters appearing to have triggered the formation of younger clusters. The area around Knot B is a particularly interesting example, with a ∼10–50 Myr old cluster of estimated mass ∼10 6 M ☉ having apparently triggered the formation of several younger, more massive (up to 5 × 10 6 M ☉ ) clusters along a dust lane. A comparison with new NICMOS observations reveals that only 16% ± 6% of the IR-bright clusters in the Antennae are still heavily obscured, with values of A V >3 mag.

(Ultra) luminous infrared galaxies ((U)LIRGs) are objects characterized by their extreme infrared (8–1000 μm) luminosities ( L LIRG > 10 11 L ☉ and L ULIRG > 10 12 L ☉ ). The Herschel Comprehensive ULIRG Emission Survey (PI: van der Werf) presents a representative flux-limited sample of 29 (U)LIRGs that spans the full luminosity range of these objects (10 11 L ☉ ⩽ L IR ⩽ 10 13 L ☉ ). With the Herschel Space Observatory , we observe [C ii ] 157 μm, [O i ] 63 μm, and [O i ] 145 μm line emission with Photodetector Array Camera and Spectrometer, CO J = 4–3 through J = 13–12, [C i ] 370 μm, and [C i ] 609 μm with SPIRE, and low- J CO transitions with ground-based telescopes. The CO ladders of the sample are separated into three classes based on their excitation level. In 13 of the galaxies, the [O i ] 63 μm emission line is self absorbed. Comparing the CO excitation to the InfraRed Astronomical Satellite 60/100 μm ratio and to far infrared luminosity, we find that the CO excitation is more correlated to the far infrared colors. We present cooling budgets for the galaxies and find fine-structure line flux deficits in the [C ii ], [Si ii ], [O i ], and [C i ] lines in the objects with the highest far IR fluxes, but do not observe this for CO 4 ⩽ J upp ⩽ 13. In order to study the heating of the molecular gas, we present a combination of three diagnostic quantities to help determine the dominant heating source. Using the CO excitation, the CO J = 1–0 linewidth, and the active galactic nucleus (AGN) contribution, we conclude that galaxies with large CO linewidths always have high-excitation CO ladders, and often low AGN contributions, suggesting that mechanical heating is important.

We present FIR [50–300 μm]−CO luminosity relations (i.e., ) for the full CO rotational ladder from J = 1–0 up to J = 13–12 for a sample of 62 local ( z ⩽ 0.1) (Ultra) Luminous Infrared Galaxies (LIRGs; L IR[8-1000 μm] > 10 11 L ☉ ) using data from Herschel SPIRE-FTS and ground-based telescopes. We extend our sample to high redshifts ( z > 1) by including 35 submillimeter selected dusty star forming galaxies from the literature with robust CO observations, and sufficiently well-sampled FIR/submillimeter spectral energy distributions (SEDs), so that accurate FIR luminosities can be determined. The addition of luminous starbursts at high redshifts enlarge the range of the FIR−CO luminosity relations toward the high-IR–luminosity end, while also significantly increasing the small amount of mid- J /high- J CO line data ( J = 5–4 and higher) that was available prior to Herschel . This new data set (both in terms of IR luminosity and J -ladder) reveals linear FIR−CO luminosity relations (i.e., α ≃ 1) for J = 1–0 up to J = 5–4, with a nearly constant normalization (β ∼ 2). In the simplest physical scenario, this is expected from the (also) linear FIR−(molecular line) relations recently found for the dense gas tracer lines (HCN and CS), as long as the dense gas mass fraction does not vary strongly within our (merger/starburst)-dominated sample. However, from J = 6–5 and up to the J = 13–12 transition, we find an increasingly sublinear slope and higher normalization constant with increasing J . We argue that these are caused by a warm (∼100 K) and dense (>10 4 cm −3 ) gas component whose thermal state is unlikely to be maintained by star-formation-powered far-UV radiation fields (and thus is no longer directly tied to the star formation rate). We suggest that mechanical heating (e.g., supernova-driven turbulence and shocks), and not cosmic rays, is the more likely source of energy for this component. The global CO spectral line energy distributions, which remain highly excited from J = 6–5 up to J = 13–12, are found to be a generic feature of the (U)LIRGs in our sample, and further support the presence of this gas component.

Full range Herschel/PACS spectroscopy of the (ultra)luminous infrared galaxies NGC 4418 and Arp 220, observed as part of the SHINING key programme, reveals high excitation in H2O, OH, HCN, and NH3. In NGC 4418, absorption lines were detected with Elower > 800 K (H2O), 600 K (OH), 1075 K (HCN), and 600 K (NH3), while in Arp 220 the excitation is somewhat lower. While outflow signatures in moderate excitation lines are seen in Arp 220 as have been seen in previous studies, in NGC 4418 the lines tracing its outer regions are redshifted relative to the nucleus, suggesting an inflow with Ṁ ≲ 12 M⊙ yr-1. Both galaxies have compact and warm (Tdust ≳ 100 K) nuclear continuum components, together with a more extended and colder component that is much more prominent and massive in Arp 220. A chemical dichotomy is found in both sources: on the one hand, the nuclear regions have high H2O abundances, ~10-5, and high HCN/H2O and HCN/NH3 column density ratios of 0.1−0.4 and 2−5, respectively, indicating a chemistry typical of evolved hot cores where grain mantle evaporation has occurred. On the other hand, the high OH abundance, with OH/H2O ratios of ~0.5, indicates the effects of X-rays and/or cosmic rays. The nuclear media have high surface brightnesses (≳1013 L⊙/kpc2) and are estimated to be very thick (NH ≳ 1025 cm-2). While NGC 4418 shows weak absorption in H218O and 18OH, with a 16O-to-18O ratio of ≳250−500, the relatively strong absorption of the rare isotopologues in Arp 220 indicates 18O enhancement, with 16O-to-18O of 70−130. Further away from the nuclear regions, the H2O abundance decreases to ≲10-7 and the OH/H2O ratio is reversed relative to the nuclear region to 2.5−10. Despite the different scales and morphologies of NGC 4418, Arp 220, and Mrk 231, preliminary evidence is found for an evolutionary sequence from infall, hot-core like chemistry, and solar oxygen isotope ratio to high velocity outflow, disruption of the hot core chemistry and cumulative high mass stellar processing of 18O.

We report measurements of the [C II] 157.74 μm fine-structure line in a sample of seven ultraluminous infrared galaxies (ULIGs) ( L IR > 10 12 L ☉ ) with the Long Wavelength Spectrometer on the Infrared Space Observatory . The [C II] line is an important coolant in galaxies and arises in interstellar gas exposed to far-ultraviolet photons ( h ν≥11.26 eV); in ULIGs, this radiation stems from the bursts of star formation and/or from the active galactic nuclei that power the tremendous infrared luminosity. The [C II] 158 μm line is detected in four of the seven ULIGs; the absolute line flux (about a few times 10 -20 W cm -2 ) represents some of the faintest extragalactic[C II] emission yet observed. Relative to the far-infrared continuum, the [C II] flux from the observed ULIGs is ~10% of that seen from nearby normal and starburst galaxies. We discuss possible causes for the [C II] deficit, namely (1) self-absorbed or optically thick [C II] emission, (2) saturation of the [C II] emission in photodissociated gas with high gas density n (≫3 × 10 3 cm -3 ) or with a high ratio of incident UV flux G 0 to n ( G 0 / n ≳ 10 cm 3 ), or (3) the presence of a soft ultraviolet radiation field caused, for example, by a stellar population deficient in massive main-sequence stars. As nearby examples of colliding galaxies, ULIGs may resemble high-redshift protogalaxies in both morphology and spectral behavior. If true, the suggested [C II] deficit in ULIGs poses limitations on the detection rate of high- z sources and on the usefulness of [C II] as an eventual tracer of protogalaxies.

Abstract We present the highest fidelity spectrum to date of a planetary-mass object. VHS 1256 b is a <20 M Jup widely separated (∼8″, a = 150 au), young, planetary-mass companion that shares photometric colors and spectroscopic features with the directly imaged exoplanets HR 8799c, d, and e. As an L-to-T transition object, VHS 1256 b exists along the region of the color–magnitude diagram where substellar atmospheres transition from cloudy to clear. We observed VHS 1256 b with JWST's NIRSpec IFU and MIRI MRS modes for coverage from 1 to 20 μm at resolutions of ∼1000–3700. Water, methane, carbon monoxide, carbon dioxide, sodium, and potassium are observed in several portions of the JWST spectrum based on comparisons from template brown dwarf spectra, molecular opacities, and atmospheric models. The spectral shape of VHS 1256 b is influenced by disequilibrium chemistry and clouds. We directly detect silicate clouds, the first such detection reported for a planetary-mass companion.

We present the results of Spitzer Infrared Spectrograph low-resolution infrared 5-35 μm spectroscopy of nearby ultraluminous infrared galaxies (ULIRGs) at z < 0.15. We focus on the search for the signatures of buried active galactic nuclei (AGNs) in the complete sample of ULIRGs classified optically as non-Seyferts (LINERs or H II regions). In addition to polycyclic aromatic hydrocarbon (PAH) emission features at 6.2, 7.7, and 11.3 μm, the conventional tool of starburst-AGN separation, we use the optical depths of the 9.7 and 18 μm silicate dust absorption features to infer the geometry of energy sources and dust at the nuclei of these ULIRGs, namely, whether the energy sources are spatially well mixed with dust (a normal starburst) or are more centrally concentrated than the dust (a buried AGN). Infrared spectra of at least 30%, and possibly 50%, of the observed optical non-Seyfert ULIRGs are naturally explained by emission consisting of (1) energetically insignificant, modestly obscured ( A V < 20-30 mag) PAH-emitting normal starbursts and (2) energetically dominant, highly dust-obscured, centrally concentrated energy sources with no PAH emission. We interpret the latter component as a buried AGN. The fraction of ULIRGs showing some buried AGN signatures is higher in LINER ULIRGs than in H II region ULIRGs. Most of the luminous buried AGN candidates are found in ULIRGs with cool far-infrared colors. Where the absorption-corrected intrinsic AGN luminosities are derivable with little uncertainty, they are found to be of the order of 10 12 L ☉ , accounting for the bulk of the ULIRGs' luminosities. The 5-35 μm spectroscopic starburst/AGN classifications are generally consistent with our previous classifications based on 3-4 μm spectra for the same sample.