Mallory Molina

We present near- and mid-infrared spectra of eight low-luminosity active galactic nuclei (LLAGN), spanning nearly 4 orders of magnitude in black hole mass and Eddington ratio, obtained with JWST/NIRSpec and MIRI as part of the ReveaLLAGN program, along with identical archival data of Cen A. The high spatial resolution of JWST cleanly separates active galactic nuclei (AGN) emission from host-galaxy contamination, enabling detections of high-ionization-potential lines more than an order of magnitude fainter than previously measured. Emission-line diagnostics reveal a transition at log( L _bol / L _Edd ) ∼−3.5, where the spectral energy distribution becomes increasingly deficient in ultraviolet photons. We find that rotational H ₂ excitation temperatures are elevated (∼500 K higher) compared to both higher-luminosity AGN and star-forming galaxies, while the H ₂ (0–0)S(3)/PAH _{11.3 μ m} ratios are consistent with those observed in the AGN population. We discuss the possible roles of outflows, jets, and X-ray-dominated regions in shaping the interstellar medium surrounding LLAGN. Silicate emission at ∼10 μ m, localized to the nuclear region, is detected in most ReveaLLAGN targets. This dataset offers the first comprehensive JWST-based characterization of infrared emission lines in the nuclear regions of LLAGN.

We present Chandra X-ray Observatory and Hubble Space Telescope (HST) follow-up observations of 12 dwarf galaxies from A. E. Reines et al. that are potential hosts of radio-selected active galactic nuclei (AGNs), eight of which are nonnuclear and possible “wandering” black holes (BHs). Our multiwavelength analysis indicates a heterogeneous sample with five radio sources detected at both X-ray and optical wavelengths within the positional uncertainties and nondetections for the remaining objects. Of the radio objects detected in the X-ray and optical, three have multiwavelength evidence for hosting nuclear massive BHs and one object is consistent with an extreme compact starburst. Only one of the off-nuclear radio sources has a significant optical counterpart and we present Palomar spectroscopy that identifies this object as a background AGN. We cannot definitively determine if the seven remaining off-nuclear radio sources are wandering massive BHs in the target dwarf galaxies or background AGNs, although the three sources with the largest offsets have compact radio cores detected with the Very Long Baseline Array and are consistent with expectations for background AGNs. Our HST sensitivity limits also allow for wandering massive BHs in the target dwarf galaxies that are hosted by stellar clusters with masses ≲ 10 ⁶ M _⊙ .

Local low-metallicity galaxies with signatures of possible accretion activity are ideal laboratories in which to search for the lowest-mass black holes and study their impact on the host galaxy. Here we present the first JWST NIRSpec IFS observations of SDSS J120122.30+021108.3, a nearby (z = 0.00354) extremely metal-poor dwarf galaxy with no optical signatures of accretion activity but identified by the Wide-field Infrared Survey Explorer to have red mid-infrared (MIR) colors consistent with active galactic nuclei (AGNs). We identify over 100 lines between ∼1.7 and 5.2 μm, an unresolved nuclear continuum source with an extremely steep spectral slope consistent with hot dust from an AGN (F _ν ≈ ν ^−1.5), and a plethora of H i, He i, and H₂ lines, with no lines from heavier elements, CO or ice absorption features, or polycyclic aromatic hydrocarbons (PAHs). While the bright central unresolved source (≲5 pc) is suggestive of an AGN, there are no He ii lines or coronal lines identified in the spectrum, and, importantly, there is no evidence that the radiation field is harder in the nuclear source compared with surrounding regions. The emission-line spectrum can be explained by a young (4 M _⊙, but the unresolved continuum source is more typical for a deeply embedded AGN powered by a black hole of minimum mass ∼1450 M _⊙. These observations reveal that either a metal-poor stellar population can heat the dust to extremely high temperatures, a result that would have significant impact on the reliability of MIR color selection in AGN surveys and our understanding of the properties of the interstellar medium and young stars in metal-poor galaxies, or an accreting intermediate-mass black hole is deeply embedded and hidden even at near-infrared wavelengths.

We present a sample of 398 galaxies with ionized gas outflow signatures in their spectra from the Galaxy and Mass Assembly Survey Data Release 4, including 45 low-mass galaxies with stellar masses M _* < 10¹⁰ M _⊙. We assemble our sample by systematically searching for the presence of a second velocity component in the [O iii]λλ4959, 5007 doublet emission line in 39,612 galaxies with redshifts z < 0.3. The host galaxies are classified using the Baldwin–Phillips–Terlevich diagram, with ~89% identified as active galactic nuclei (AGNs) and composites and 11% as star-forming (SF) galaxies. The outflows are typically faster in AGNs with a median velocity of 936 km s⁻¹ compared to 655 km s⁻¹ in the SF objects. Of particular interest are the 45 galaxies in the low-mass range, of which a third are classified as AGNs/composites. The outflows from the low-mass AGNs are also faster and more blueshifted compared to those in the low-mass SF galaxies. This indicates that black hole outflows can affect host galaxies in the low-mass range and that AGN feedback in galaxies with M _* < 10¹⁰ M _⊙ should be considered in galaxy evolution models.

We present the first results from the Revealing Low-Luminosity Active Galactic Nuclei (ReveaLLAGN) survey, a JWST survey of seven nearby LLAGNs. We focus on two observations with the Mid-Infrared Instrument (MIRI)’s Medium-Resolution Spectrometer of the nuclei of NGC 1052 and Sombrero (NGC 4594/M104). We also compare these data to public JWST data of higher-luminosity AGNs, NGC 7319 and NGC 7469. JWST clearly separates the AGN spectrum from the galaxy light even in Sombrero, the faintest target in our survey; the AGN components have very red spectra. We find that the emission-line widths in both NGC 1052 and Sombrero increase with increasing ionization potential, with FWHM > 1000 km s⁻¹ for lines with ionization potential ≳ 50 eV. These lines are also significantly blueshifted in both LLAGNs. The high-ionization-potential lines in NGC 7319 show neither broad widths nor significant blueshifts. Many of the lower-ionization-potential emission lines in Sombrero show significant blue wings extending >1000 km s⁻¹. These features and the emission-line maps in both galaxies are consistent with outflows along the jet direction. Sombrero has the lowest-luminosity high-ionization-potential lines ([Ne v] and [O iv]) ever measured in the mid-infrared, but the relative strengths of these lines are consistent with higher-luminosity AGNs. On the other hand, the [Ne v] emission is much weaker relative to the [Ne iii] and [Ne ii] lines of higher-luminosity AGNs. These initial results show the great promise that JWST holds for identifying and studying the physical nature of LLAGNs.

We develop a novel approach to measure the dust attenuation properties of galaxies, including the dust opacity, the shape of the attenuation curve, and the strength of the 2175 Å absorption feature. From an observed spectrum, the method uses a model-independent approach to derive a relative attenuation curve with an absolute amplitude calibrated using NIR photometry. The dust-corrected spectrum is fitted with stellar population models to derive the dust-free model spectrum, which is compared with the observed SED/spectrum from NUV to NIR to determine the dust attenuation properties. We apply this method to investigate dust attenuation on kiloparsec scales using a sample of 134 galaxies with integral field spectroscopy from MaNGA, NIR imaging from 2MASS, and NUV imaging from Swift/UVOT. We find that the attenuation curve slope and the 2175 Å bump in both the optical and NUV span a wide range at kiloparsec scales. The slope is shallower at higher optical opacity, regardless of the specific star formation rate (sSFR), the minor-to-major axis ratio (b/a) of the galaxies, and the location of spaxels within individual galaxies. The 2175 Å bump presents a strong negative correlation with the sSFR, while the correlations with the optical opacity, b/a, and the locations within individual galaxies are all weak. All of these trends appear to be independent of the stellar mass of the galaxies. Our results support the scenario that the variation of the 2175 Å bump is driven predominantly by processes related to star formation, such as the destruction of small dust grains by UV radiation in star-forming regions.

We present the the new Swift/UVOT+MaNGA (SwiM) catalog (SwiM_v4.1). SwiM_v4.1 is designed to study star formation and dust attenuation within nearby galaxies given the unique overlap of Swift/UVOT near-ultraviolet (NUV) imaging and MaNGA integral field optical spectroscopy. SwiM_v4.1 comprises 559 objects, ∼4 times more than the original SwiM catalog (SwiM_v3.1), spans the redshift range z ≈ 0.0002–0.1482, and provides a more diverse and rich sample. Approximately 5% of the final MaNGA sample is included in SwiM_v4.1, and 42% of the SwiM_v4.1 galaxies are cross-listed with other well-known catalogs. We present the same data as SwiM_v3.1, including UVOT images, Sloan Digital Sky Survey (SDSS) images, and MaNGA emission-line and spectral index maps with the same pixel size and angular resolution for each galaxy, and a file containing galaxy and observational properties. We designed SwiM_v4.1 to be unbiased, which resulted in some objects having low signal-to-noise ratios in their MaNGA or Swift data. We addressed this by providing a new file containing the fraction of science-ready pixels in each MaNGA emission-line map, and the integrated flux and inverse variance for all three NUV filters. The uniform angular resolution and sampling in SwiM_v4.1 will help answer a number of scientific questions, including constraining quenching and attenuation in the local Universe and studying the effects of black hole feedback. The galaxy maps, catalog files, and their associated data models are publicly released on the SDSS website (a description of the SwiM VAC is provided at https://www.sdss4.org/dr17/data_access/value-added-catalogs/?vac_id=swift-manga-value-added-catalog, and the data are stored on the SDSS Science Archive Server at https://data.sdss.org/sas/dr17/manga/swim/v4.1/).

We develop a novel approach to measure dust attenuation properties of galaxies, including the dust opacity, shape of the attenuation curve and the strength of the 2175{\AA} absorption feature. From an observed spectrum, the method uses a model-independent approach to derive a relative attenuation curve, with absolute amplitude calibrated using NIR photometry. The dust-corrected spectrum is fitted with stellar population models to derive the dust-free model spectrum, which is compared with the observed SED/spectrum from NUV to NIR to determine dust attenuation properties. We apply this method to investigate dust attenuation on kpc scales, using a sample of 134 galaxies with integral field spectroscopy from MaNGA, NIR imaging from 2MASS, and NUV imaging from Swift/UVOT. We find the attenuation curve slope and the 2175{\AA} bump in both optical and NUV span a wide range at kpc scales. The slope is shallower at higher optical opacity, regardless of the specific star formation rate (sSFR), minor-to-major axis ratio (b/a) of galaxies and the location of spaxels within individual galaxies. The 2175{\AA} bump presents a strong negative correlation with the sSFR, while the correlations with the optical opacity, b/a and the location within individual galaxies are all weak. All these trends appear to be independent of the stellar mass of galaxies. Our results support the scenario that the variation of the 2175{\AA} bump is driven predominantly by processes related to star formation, such as the destruction of small dust grains by UV radiation in star-forming regions.