arXiv subjects

Raymond P. Remigio

Publications and source records attributed to Raymond P. Remigio.

8 recordsLinked to original sources

arXiv2026

Clumpy Disk, Interloper, or Merger? Nature of a Distant Galaxy Pair at 5 kpc Projected Separation

We present the morphological, photometric, and spectroscopic properties of a z ~ 1 galaxy, "lil gal", serendipitously detected in JWST Mid Infrared Instrument (MIRI) images of nearby galaxy VV 340. In the MIRI F560W and F770W images, we identify what appears to be a spiral galaxy with a central bulge. However, in the F1500W image, a second peak appears ~0.7" northwest (NW) from the central bulge, calling into question the nature of this source as a clumpy disk, a high-redshift interloper, or a galaxy merger. Multi-band analyses of the three MIRI and four Hubble Space Telescope (HST) images suggest a photometric redshift of ~0.92. Spectroscopic analyses of data from the Keck Near-Infrared Echellette Spectrometer (NIRES) reveal two sets of [N II] and H-alpha emission lines corresponding to the two observed sources. A redshift of z = 0.9248 is identified for the NW companion. Fainter emission lines are identified from the underlying galaxy at z = 0.9225, suggesting a merging galaxy pair at a projected separation of ~5 kpc. From the emission line ratios from Keck NIRES and Keck Cosmic Web Imager (KCWI) spectra, we classify the system as hosting regions of active star formation, likely attributed to merger-induced starburst activity. The results demonstrate the necessity of resolved, spectroscopic follow-up analyses of galaxies found in deep JWST images to disentangle the role of galaxy mergers from clumpy disk galaxies at z ~ 1 to cosmic noon and beyond.

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arXiv2026

Detection of an Extended Ly$α$ Halo around a $\textit{z}=6.64$ Broad Absorption Line Quasar with the Keck Cosmic Web Imager

We present the first results from a program searching for extended Ly$α$ halos around high redshift ($ z \gtrsim 6.5$) quasars using the red channel of the Keck Cosmic Web Imager (KCWI). Our observations reveal a Ly$α$ halo extending to $\simeq11$ pkpc around the $z=6.64$ broad absorption line quasar J0910$-$0414. The Ly$α$ velocity field displays a rotation-like gradient, and the gas velocity dispersion is consistent with gravitationally dominated motion ($σ_{\mathrm{Lyα}}<300$ km s$^{-1}$). Comparison with the $[\mathrm{C\;II}]$ kinematics of the host galaxy core from ALMA observations shows that the Ly$α$-emitting gas extends over a much larger region, shows distinct kinematics, and has a smaller velocity dispersion ($σ_{\mathrm{Lyα}} \simeq 0.6σ_{\mathrm{[C\;II]}}$). The Ly$α$ spectral region of the quasar is largely obscured by a deep $\mathrm{N\;V}$ absorption trough, and as a result, roughly $55\%$ of the total Ly$α$ flux is from the extended halo. These observations demonstrate the potential of KCWI for probing the cool gas reservoir that fuels the growth of quasars and their hosts in the epoch of reionization.

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arXiv2026

The Host Galaxies of Active Galactic Nuclei with Direct Black Hole Mass Measurements

Reverberation mapping (RM) determines the mass of black holes (BH) in active galactic nuclei (AGNs) by resolving the BH gravitational sphere of influence in the time domain. Recent RM campaigns yielded direct BH masses through dynamical modeling for a sample of 32 objects, spanning a wide range of AGN luminosities and BH masses. In addition, accurate BH masses have been determined by spatially resolving the broad-line region with GRAVITY for a handful of AGNs. Here, we present a detailed analysis of Hubble Space Telescope images using surface-brightness profile fitting with state-of-the-art programs. We derive AGN luminosity and host-galaxy properties, such as radii and luminosities for spheroid, disk, and bar (if present). The spheroid effective radii were used to measure stellar velocity dispersion from integral-field spectroscopy. Since the BH masses of our sample do not depend on any assumption of the virial factor needed in single-epoch spectroscopic mass estimates, we can show that the resulting scaling relations between the mass of the supermassive BHs and their host galaxies match those of quiescent galaxies, naturally extending to lower masses in these (predominantly) spiral galaxies. We find that the inner AGN orientation, as traced by the broad-line region inclination angle, is uncorrelated with the host-galaxy disk. Our sample has the most direct and accurate MBH measurements of any AGN sample and provides a fundamental local benchmark for studies of the evolution of massive black holes and their host galaxies across cosmic time.

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arXiv2025

Spatially Resolved [O III] Emission Line Kinematics of Reverberation-Mapped AGNs with the Keck Cosmic Web Imager

We present optical integral-field spectroscopic data of ten nearby ($0.02\leq z \leq 0.05$) Seyfert 1 galaxies taken with the Keck Cosmic Web Imager (KCWI). We map the spatially resolved kinematics of the [O III] gas and stars, and investigate the alignments between their global kinematic position angles (PA). Large-scale gas motions are primarily dominated by rotation, and are kinematically aligned with the stars ($Δ\text{PA}\leq 30$ deg). However, eight galaxies exhibit non-rotational kinematic signatures (e.g., kinematic twists, possible outflows) in their ionized gas velocity fields near the nucleus. We compare aperture-wide measurements of the gas and stellar velocity dispersions ($σ_{\text{gas}}$ and $σ_\star$) to test the use of the width of the [O III] line core as a surrogate for $σ_\star$. Direct comparisons between $σ_{\text{gas}}$ and $σ_\star$ show that $σ_{\text{gas}}$ tends to underestimate $σ_\star$, and thus is not a reliable tracer of $σ_\star$ for our selected galaxies. We measure the extent of the narrow-line region (NLR) using several definitions, resulting in sizes of $\sim0.1$-$10$ kpc. For a given [O III] luminosity, our NLR sizes derived from the [O III]/H$β$ flux ratio or an [O III] isophotal radius are an order of magnitude larger than those measured from past imaging data.

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arXiv2024

Combining Direct Black Hole Mass Measurements and Spatially Resolved Stellar Kinematics to Calibrate the $M_{\rm BH}$-$σ_\star$ Relation of Active Galaxies

The origin of the tight scaling relation between the mass of supermassive black holes (SMBHs; $M_{\rm BH}$) and their host-galaxy properties remains unclear. Active galactic nuclei (AGNs) probe phases of ongoing SMBH growth and offer the only opportunity to measure $M_{\rm BH}$ beyond the local Universe. However, determining AGN host galaxy stellar velocity dispersion $σ_\star$, and their galaxy dynamical masses $M_{\rm dyn}$, is complicated by AGN contamination, aperture effects and different host galaxy morphologies. We select a sample of AGNs for which $M_{\rm BH}$ has been independently determined to high accuracy by state-of-the-art techniques: dynamical modeling of the reverberation signal and spatially resolving the broad-line region with VLTI/GRAVITY. Using IFU observations, we spatially map the host galaxy stellar kinematics across the galaxy and bulge effective radii. We find that that the dynamically hot component of galaxy disks correlates with $M_{\rm BH}$; however, the correlations are tightest for aperture-integrated $σ_\star$ measured across the bulge. Accounting for the different $M_{\rm BH}$ distributions, we demonstrate - for the first time - that AGNs follow the same $M_{\rm BH}$-$σ_\star$ and $M_{\rm BH}$-$M_{\rm bulge, dyn}$ relations as quiescent galaxies. We confirm that the classical approach of determining the virial factor as sample-average, yielding ${\rm log }f= 0.65 \pm 0.18$, is consistent with the average $f$ from individual measurements. The similarity between the underlying scaling relations of AGNs and quiescent galaxies implies that the current AGN phase is too short to have altered BH masses on a population level. These results strengthen the local calibration of $f$ for measuring single-epoch $M_{\rm BH}$ in the distant Universe.

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arXiv2024

GOALS-JWST: Gas Dynamics and Excitation in NGC7469 revealed by NIRSpec

We present new JWST-NIRSpec IFS data for the luminous infrared galaxy NGC7469: a nearby (70.6Mpc) active galaxy with a Sy 1.5 nucleus that drives a highly ionized gas outflow and a prominent nuclear star-forming ring. Using the superb sensitivity and high spatial resolution of the JWST instrument NIRSpec-IFS, we investigate the role of the Seyfert nucleus in the excitation and dynamics of the circumnuclear gas. Our analysis focuses on the [Fe ii], H2, and hydrogen recombination lines that trace the radiation/shocked-excited molecular and ionized ISM around the AGN. We investigate the gas excitation through H2/Brγ and [Fe ii]/Pa\b{eta} emission line ratios and find that photoionization by the AGN dominates within the central 300 pc of the galaxy and together with a small region show ing signatures of shock-heated gas; these shock-heated regions are likely associated with a compact radio jet. In addition, the velocity field and velocity dispersion maps reveal complex gas kinematics. Rotation is the dominant feature, but we also identify non-circular motions consistent with gas inflows as traced by the velocity residuals and the spiral pattern in the Paα velocity dispersion map. The inflow is consistent with the mass outflow rate and two orders of magnitude higher than the AGN accretion rate. The compact nuclear radio jet has enough power to drive the highly ionized outflow. This scenario suggests that the inflow and outflow are in a self-regulating feeding-feedback process, with a contribution from the radio jet helping to drive the outflow.

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arXiv2022

GOALS-JWST: Resolving the Circumnuclear Gas Dynamics in NGC 7469 in the Mid-Infrared

The nearby, luminous infrared galaxy (LIRG) NGC 7469 hosts a Seyfert nucleus with a circumnuclear star-forming ring and is thus the ideal local laboratory for investigating the starburst--AGN connection in detail. We present integral-field observations of the central 1.3 kpc region in NGC 7469 obtained with the JWST Mid-InfraRed Instrument. Molecular and ionized gas distributions and kinematics at a resolution of {\sim}100 pc over the 4.9 - 7.6μm region are examined to study gas dynamics influenced by the central AGN. The low-ionization [Fe II] λ5.34μm and [Ar II] λ6.99μm lines are bright on the nucleus and in the starburst ring, as opposed to H2 S(5) λ6.91μm which is strongly peaked at the center and surrounding ISM. The high-ionization [Mg V] line is resolved and shows a broad, blueshifted component associated with the outflow. It has a nearly face-on geometry that is strongly peaked on the nucleus, where it reaches a maximum velocity of -650 km/s, and extends about 400 pc to the East. Regions of enhanced velocity dispersion in H2 and [Fe II] {\sim}180 pc from the AGN that also show high L(H2)/L(PAH) and L([Fe II])/L(Pfα) ratios to the W and N of the nucleus pinpoint regions where the ionized outflow is depositing energy, via shocks, into the dense interstellar medium between the nucleus and the starburst ring. These resolved mid-infrared observations of the nuclear gas dynamics demonstrate the power of JWST and its high-sensitivity integral-field spectroscopic capability to resolve feedback processes around supermassive black holes in the dusty cores of nearby LIRGs.

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arXiv2021

H$α$ Reverberation Mapping of the Intermediate-Mass Active Galactic Nucleus in NGC 4395

We present the results of a high-cadence spectroscopic and imaging monitoring campaign of the active galactic nucleus (AGN) of NGC 4395. High signal-to-noise-ratio spectra were obtained at the Gemini-N 8 m telescope using the GMOS integral field spectrograph (IFS) on 2019 March 7, and at the Keck-I 10 m telescope using the Low-Resolution Imaging Spectrometer (LRIS) with slitmasks on 2019 March 3 and April 2. Photometric data were obtained with a number of 1 m-class telescopes during the same nights. The narrow-line region (NLR) is spatially resolved; therefore, its variable contributions to the slit spectra make the standard procedure of relative flux calibration impractical. We demonstrate that spatially-resolved data from the IFS can be effectively used to correct the slit-mask spectral light curves. While we obtained no reliable lag owing to the lack of strong variability pattern in the light curves, we constrain the broad line time lag to be less than 3 hr, consistent with the photometric lag of $\sim80$ min reported by Woo et al. (2019). By exploiting the high-quality spectra, we measure the second moment of the broad component of the H$α$ emission line to be $586\pm19$ km s$^{-1}$, superseding the lower value reported by Woo et al. (2019). Combining the revised line dispersion and the photometric time lag, we update the black hole mass as $(1.7\pm 0.3)\times10^4$ M$_{\odot}$.

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