arXiv subjects

Edmund Hodges-Kluck

Publications and source records attributed to Edmund Hodges-Kluck.

At least 55 records · Page 3Linked to original sources

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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arXiv2021

Proof of CMB-driven X-ray brightening of high-z radio galaxies

We present a definitive assessment of the role of Inverse Compton scattering of Cosmic Microwave Background photons (IC/CMB) in the context of radio galaxies. Owing to the steep increase of the CMB radiation energy density, IC/CMB is supposed to become progressively more important with respect to radio synchrotron cooling as the redshift increases. For typical energies at play, this process will up-scatter the CMB photons into the X-ray band, and is thus expected to yield a redshift-dependent, concurrent X-ray brightening and radio dimming of the jet-powered structures. Here we show how a conclusive proof of this effect hinges on high-resolution imaging data in which the extended lobes can be distinguished from the compact hot spots where synchrotron-self-Compton dominates the X-ray emission regardless of redshift. We analyze Chandra and Very Large Array data of 11 radio galaxies between 1.3 3 radio galaxies below <1 mJy, IC/CMB alone can not be responsible for a deficit in high-z, radio-loud AGN if--as we argue--such AGN typically have bright, compact hot spots.

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arXiv2020

A 60-kpc Galactic Wind Cone in NGC 3079

Galactic winds are associated with intense star formation and AGNs. Depending on their formation mechanism and velocity they may remove a significant fraction of gas from their host galaxies, thus suppressing star formation, enriching the intergalactic medium, and shaping the circumgalactic gas. However, the long-term evolution of these winds remains mostly unknown. We report the detection of a wind from NGC 3079 to at least 60 kpc from the galaxy. We detect the wind in FUV line emission to 60 kpc (as inferred from the broad FUV filter in GALEX) and in X-rays to at least 30~kpc. The morphology, luminosities, temperatures, and densities indicate that the emission comes from shocked material, and the O/Fe ratio implies that the X-ray emitting gas is enriched by Type II supernovae. If so, the speed inferred from simple shock models is about 500 km/s, which is sufficient to escape the galaxy. However, the inferred kinetic energy in the wind from visible components is substantially smaller than canonical hot superwind models.

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arXiv2020

Extended X-ray emission from the z=4.26 radio galaxy 4C 63.20

We report on deep Chandra X-ray Telescope imaging observations of 4C 63.20, one of the few known radio galaxies at z>3.5. The X-ray counterpart is resolved into a core plus two off-nuclear sources that (combined) account for close to 30% of the total X-ray flux. Their morphology and orientation are consistent with a diffuse, lobe-like nature, albeit compact hotspots cannot be ruled out. The broadband spectral energy distribution of 4C 63.20 can be reproduced with a jet model where the majority of the radio flux can be ascribed to synchrotron emission from the hotspots, whereas the (non-nuclear) X-ray emission is produced via Inverse Compton (IC) off of Cosmic Microwave Background (CMB) photons within the extended lobes. This scenario is broadly consistent with the expectation from highly magnetized lobes in a hotter CMB, and supports the view that IC/CMB may quench less extreme radio lobes at high redshifts.

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arXiv2020

Ultraviolet and X-ray Properties of Coma's Ultra-Diffuse Galaxies

Many ultra-diffuse galaxies (UDGs) have been discovered in the Coma cluster, and there is evidence that some, notably Dragonfly 44, have Milky Way-like dynamical masses despite dwarf-like stellar masses. We used X-ray, UV, and optical data to investigate the star formation and nuclear activity in the Coma UDGs, and we obtained deep UV and X-ray data (Swift and XMM-Newton) for Dragonfly 44 to search for low-level star formation, hot circumgalactic gas, and the integrated emission from X-ray binaries. Among the Coma UDGs, we find UV luminosities consistent with quiescence but NUV$-r$ colors indicating star formation in the past Gyr. This indicates that the UDGs were recently quenched. The $r$-band luminosity declines with projected distance from the Coma core. The Dragonfly 44 UV luminosity is also consistent with quiescence, with SFR$<6\times 10^{-4} M_{\odot}$ yr$^{-1}$, and no X-rays are detected down to a sensitivity of $10^{38}$ erg s$^{-1}$. This rules out a hot corona with a $M > 10^8 M_{\odot}$ within the virial radius, which would normally be expected for a dynamically massive galaxy. The absence of bright, low mass X-ray binaries is consistent with the expectation from the galaxy total stellar mass, but it is unlikely if most low-mass X-ray binaries form in globular clusters, as Dragonfly 44 has a very large population. Based on the UV and X-ray analysis, the Coma UDGs are consistent with quenched dwarf galaxies, although we cannot rule out a dynamically massive population.

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arXiv2020

Nuclear X-ray Activity in Low-Surface-Brightness Galaxies: Prospects for Constraining the Local Black Hole Occupation Fraction with a Chandra Successor Mission

About half of nearby galaxies have a central surface brightness >1 magnitude below that of the sky. The overall properties of these low-surface-brightness galaxies (LSBGs) remain understudied, and in particular we know very little about their massive black hole population. This gap must be closed to determine the frequency of massive black holes at z=0 as well as to understand their role in regulating galaxy evolution. Here we investigate the incidence and intensity of nuclear, accretion-powered X-ray emission in a sample of 32 nearby LSBGs with the Chandra X-ray Observatory. A nuclear X-ray source is detected in 4 galaxies (12.5%). Based on an X-ray binary contamination assessment technique developed for normal galaxies, we conclude that the detected X-ray nuclei indicate low-level accretion from massive black holes. The active fraction is consistent with that expected from the stellar mass distribution of the LSBGs, but not their total baryonic mass, when using a scaling relation from an unbiased X-ray survey of normal galaxies. This suggests that their black holes co-evolved with their stellar population. In addition, the apparent agreement nearly doubles the number of galaxies available within ~100 Mpc for which a measurement of nuclear activity can efficiently constrain the frequency of black holes as a function of stellar mass. We conclude by discussing the feasibility of measuring this occupation fraction to a few percent precision below 1e10 solar masses with high-resolution, wide-field X-ray missions currently under consideration.

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arXiv2020

A Coupled Analysis of Atmospheric Mass Loss and Tidal Evolution in XUV Irradiated Exoplanets: the TRAPPIST-1 Case Study

Exoplanets residing close to their stars can experience evolution of both their physical structures and their orbits due to the influence of their host stars. In this work, we present a coupled analysis of dynamical tidal dissipation and atmospheric mass loss for exoplanets in XUV irradiated environments. As our primary application, we use this model to study the TRAPPIST-1 system, and place constraints on the interior structure and orbital evolution of the planets. We start by reporting on a UV continuum flux measurement (centered around $\sim1900$ Angstroms) for the star TRAPPIST-1, based on 300 ks of Neil Gehrels Swift Observatory data, and which enables an estimate of the XUV-driven thermal escape arising from XUV photo-dissociation for each planet. We find that the X-ray flaring luminosity, measured from our X-ray detections, of TRAPPIST-1 is 5.6 $\times$10$^{-4} L_{*}$, while the full flux including non-flaring periods is 6.1 $\times$10$^{-5} L_{*}$, when $L_{*}$ is TRAPPIST-1's bolometric luminosity. We then construct a model that includes both atmospheric mass-loss and tidal evolution, and requires the planets to attain their present-day orbital elements during this coupled evolution. We use this model to constrain the ratio $Q'=3Q/2k_{2}$ for each planet. Finally, we use additional numerical models implemented with the Virtual Planet Simulator \texttt{VPLanet} to study ocean retention for these planets using our derived system parameters.

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arXiv2020

Variability and the size-luminosity relation of the intermediate mass AGN in NGC 4395

We present the variability study of the lowest-luminosity Seyfert 1 galaxy NGC 4395 based on the photometric monitoring campaigns in 2017 and 2018. Using 22 ground-based and space telescopes, we monitored NGC 4395 with a $\sim$5 minute cadence during a period of 10 days and obtained light curves in the UV, V, J, H, and K/Ks bands as well as the H$α$ narrow-band. The RMS variability is $\sim$0.13 mag on \emph{Swift}-UVM2 and V filter light curves, decreasing down to $\sim$0.01 mag on K filter. After correcting for continuum contribution to the H$α$ narrow-band, we measured the time lag of the H$α$ emission line with respect to the V-band continuum as ${55}^{+27}_{-31}$ to ${122}^{+33}_{-67}$ min. in 2017 and ${49}^{+15}_{-14}$ to ${83}^{+13}_{-14}$ min. in 2018, depending on the assumption on the continuum variability amplitude in the H$α$ narrow-band. We obtained no reliable measurements for the continuum-to-continuum lag between UV and V bands and among near-IR bands, due to the large flux uncertainty of UV observations and the limited time baseline. We determined the AGN monochromatic luminosity at 5100Å $λL_λ= \left(5.75\pm0.40\right)\times 10^{39}\,\mathrm{erg\,s^{-1}}$, after subtracting the contribution of the nuclear star cluster. While the optical luminosity of NGC 4395 is two orders of magnitude lower than that of other reverberation-mapped AGNs, NGC 4395 follows the size-luminosity relation, albeit with an offset of 0.48 dex ($\geq$2.5$σ$) from the previous best-fit relation of Bentz et al. (2013).

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arXiv2020

The Warm Gas in the MW: A Kinematical Model

We develop a kinematical model for the Milky Way Si IV-bearing gas to determine its density distribution and kinematics. This model is constrained by a column density line shape sample extracted from the {\it HST}/COS archival data, which contains 186 AGN sight lines. We find that the Si IV ion density distribution is dominated by an extended disk along the $z$-direction (above or below the midplane), i.e., $n(z)=n_0\exp(-(z/z_0)^{0.82})$, where $z_0$ is the scale height of $6.3_{-1.5}^{+1.6}$ kpc (northern hemisphere) and $3.6_{-0.9}^{+1.0}$ kpc (southern hemisphere). The density distribution of the disk in the radial direction shows a sharp edge at $15-20$ kpc given by, $n(r_{\rm XY})=n_0\exp(-(r_{\rm XY}/r_0)^{3.36})$, where $r_0 \approx 12.5\pm0.6$ kpc. The difference of density distributions over $r_{\rm XY}$ and $z$ directions indicates that the warm gas traced by \ion{Si}{4} is mainly associated with disk processes (e.g., feedback or cycling gas) rather than accretion. We estimate the mass of the warm gas (within 50 kpc) is $\log (M(50 {\rm kpc})/M_\odot)\approx8.1$ (assuming $Z\approx0.5Z_\odot$), and a $3σ$ upper limit of $\log (M(250 {\rm kpc})/M_\odot)\approx9.1$ (excluding the Magellanic system). Kinematically, the warm gas disk is nearly co-rotating with the stellar disk at $v_{\rm rot}=215\pm3\rm~km~s^{-1}$, which lags the midplane rotation by about $8\rm~km~s^{-1}~kpc^{-1}$ (within 5 kpc). Meanwhile, we note that the warm gas in the northern hemisphere has significant accretion with $v_{\rm acc}$ of $69\pm 7\rm ~km~s^{-1}$ at 10 kpc (an accretion rate of $-0.60_{-0.13}^{+0.11}~M_\odot\rm~yr^{-1}$), while in the southern hemisphere, there is no measurable accretion, with an upper limit of $0.4~M_\odot\rm~yr^{-1}$.

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arXiv2020

A Second Look at 12 Candidate Dual AGNs using ${\tt BAYMAX}$

We present an analysis of 12 optically selected dual AGN candidates at $z < 0.34$. Each candidate was originally identified via double-peaked [O III] $λ$5007 emission lines, and have received follow-up $Chandra$ and $HST$ observations. Because the X-ray data are low-count ($<100$ counts) with small separations ($<1$"), a robust analysis is necessary for classifying each source. Pairing long-slit [O III] observations with existing $Chandra$ observations, we re-analyze the X-ray observations with ${\tt BAYMAX}$ to determine whether the X-ray emission from each system is more likely a single or dual point source. We find that 4 of the 12 sources are likely dual X-ray point source systems. We examine each point source's spectra via a Monte Carlo method that probabilistically identifies the likely origin of each photon. When doing so, we find that (i) the secondary X-ray point sources in 2 of the systems have $L_{\mathrm{X}}<10^{40}$ erg s$^{-1}$, such that we cannot rule out a non-AGN origin, (ii) one source has a secondary with $L_{\mathrm{X}}>10^{40}$ erg s$^{-1}$ but a spectrum that is too soft to definitively preclude being X-ray emitting diffuse gas that was photoionized by the primary AGN, and (iii) one system (SDSS J1126+2944) is a dual AGN. Additionally, using complementary $HST$ observations, we analyze a sub-sample of systems that are visually identified as merging. Our results suggest that dual AGNs may preferentially reside in mergers with small separations, consistent with both simulations and observations.

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arXiv2019

The Seoul National University AGN monitoring project. II. BLR size and black hole mass of two AGNs

Active galactic nuclei (AGNs) show a correlation between the size of the broad line region (BLR) and the monochromatic continuum luminosity at 5100 Å, allowing black hole mass estimation based on single-epoch spectra. However, the validity of the correlation is yet to be clearly tested for high-luminosity AGNs. We present the first reverberation-mapping results of the Seoul National University AGN monitoring program (SAMP), which is designed to focus on luminous AGNs for probing the high end of the size-luminosity relation. We report time lag measurements of two AGNs, namely, 2MASS J10261389+5237510 and SDSS J161911.24+501109.2, using the light curves obtained over a $\sim$1000 day period with an average cadence of $\sim$10 and $\sim$20 days, respectively for photometry and spectroscopy monitoring. Based on a cross-correlation analysis and H$β$ line width measurements, we determine the H$β$ lag as $41.8^{+4.9}_{-6.0}$ and $52.6^{+17.6}_{-14.7}$ days in the observed-frame, and black hole mass as $3.65^{+0.49}_{-0.57} \times 10^7 M_{\odot}$ and $23.02^{+7.81}_{-6.56} \times 10^7 M_{\odot}$, respectively for 2MASS J1026 and SDSS J1619.

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arXiv2019

A 10,000-solar-mass black hole in the nucleus of a bulgeless dwarf galaxy

The motions of gas and stars in the nuclei of nearby large galaxies have demonstrated that massive black holes are common and that their masses strongly correlate with the stellar velocity dispersion $σ_{\star}$ of the bulge. This correlation suggests that massive black holes and galaxies influence each other's growth. Dynamical measurements are less reliable when the sphere of influence is unresolved, thus it remains unknown whether this correlation exists in galaxies much smaller than the Milky Way, as well as what fraction of these galaxies have central black holes. Light echoes from photoionized clouds around accreting black holes, in combination with the velocity of these clouds, yield a direct mass measurement that circumvents this difficulty. Here we report an exceptionally low reverberation delay of $83\pm14$ minutes between variability in the accretion disk and high velocity H$α$ emission from the nucleus of the bulgeless dwarf galaxy NGC~4395. Combined with the H$α$ line-of-sight velocity dispersion $σ_{\rm line}=426\pm1$~km~s$^{-1}$, this lag determines a mass of about 10,000~$M_{\odot}$ for the black hole. This mass is among the smallest central black hole masses reported, near the low end of expected masses for heavy "seeds", and the best direct mass measurement for a galaxy of this size. Despite the lack of a bulge, NGC~4395 is consistent with the $M_{\rm BH} - σ_{\star}$ relation when $σ_{\star}$ is measured from the central region. This indicates that the relation need not originate from hierarchical galaxy assembly nor from black hole feedback.

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arXiv2019

Astro 2020: Astromineralogy of interstellar dust with X-ray spectroscopy

X-ray absorption fine structure (XAFS) in the 0.2-2 keV band is a crucial component in multi-wavelength studies of dust mineralogy, size, and shape -- parameters that are necessary for interpreting astronomical observations and building physical models across all fields, from cosmology to exoplanets. Despite its importance, many fundamental questions about dust remain open. What is the origin of the dust that suffuses the interstellar medium (ISM)? Where is the missing interstellar oxygen? How does iron, predominantly produced by Type Ia supernovae, become incorporated into dust? What is the main form of carbon in the ISM, and how does it differ from carbon in stellar winds? The next generation of X-ray observatories, employing microcalorimeter technology and $R \equiv λ/Δλ\geq 3000$ gratings, will provide pivotal insights for these questions by measuring XAFS in absorption and scattering. However, lab measurements of mineralogical candidates for astrophysical dust, with R > 1000, are needed to fully take advantage of the coming observations.

astro-ph.EP↗

arXiv2019

A Bayesian Analysis of SDSS J0914+0853, a Low-Mass Dual AGN Candidate

We present the first results from BAYMAX (Bayesian AnalYsis of Multiple AGN in X-rays), a tool that uses a Bayesian framework to quantitatively evaluate whether a given Chandra observation is more likely a single or dual point source. Although the most robust method of determining the presence of dual AGNs is to use X-ray observations, only sources that are widely separated relative to the instrument PSF are easy to identify. It becomes increasingly difficult to distinguish dual AGNs from single AGNs when the separation is on the order of Chandra's angular resolution (<1''). Using likelihood models for single and dual point sources, BAYMAX quantitatively evaluates the likelihood of an AGN for a given source. Specifically, we present results from BAYMAX analyzing the lowest-mass dual AGN candidate to date, SDSS J0914+0853, where archival Chandra data shows a possible secondary AGN ~0.3'' from the primary. Analyzing a new 50 ks Chandra observation, results from BAYMAX shows that SDSS J0914+0853 is most likely a single AGN with a Bayes factor of 13.5 in favor of a single point source model. Further, posterior distributions from the dual point source model are consistent with emission from a single AGN. We find the probability of SDSS J0914+0853 being a dual AGN system with a flux ratio f>0.3 and separation r>0.3'' to be very low. Overall, BAYMAX will be an important tool for correctly classifying candidate dual AGNs in the literature, and studying the dual AGN population where past spatial resolution limits have prevented systematic analyses.

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arXiv2019

A Survey of Hot Gas in the Universe

A large fraction of the baryons and most of the metals in the Universe are unaccounted for. They likely lie in extended galaxy halos, galaxy groups, and the cosmic web, and measuring their nature is essential to understanding galaxy formation. These environments have virial temperatures >10^5.5 K, so the gas should be visible in X-rays. Here we show the breakthrough capabilities of grating spectrometers to 1) detect these reservoirs of hidden metals and mass, and 2) quantify hot gas flows, turbulence, and rotation around the Milky Way and external galaxies. Grating spectrometers are essential instruments for future X-ray missions, and existing technologies provide 50-1500-fold higher throughput compared to current orbiting instruments.

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arXiv2019

Supermassive Black Hole Feedback

Understanding the processes that drive galaxy formation and shape the observed properties of galaxies is one of the most interesting and challenging frontier problems of modern astrophysics. We now know that the evolution of galaxies is critically shaped by the energy injection from accreting supermassive black holes (SMBHs). However, it is unclear how exactly the physics of this feedback process affects galaxy formation and evolution. In particular, a major challenge is unraveling how the energy released near the SMBHs is distributed over nine orders of magnitude in distance throughout galaxies and their immediate environments. The best place to study the impact of SMBH feedback is in the hot atmospheres of massive galaxies, groups, and galaxy clusters, which host the most massive black holes in the Universe, and where we can directly image the impact of black holes on their surroundings. We identify critical questions and potential measurements that will likely transform our understanding of the physics of SMBH feedback and how it shapes galaxies, through detailed measurements of (i) the thermodynamic and velocity fluctuations in the intracluster medium (ICM) as well as (ii) the composition of the bubbles inflated by SMBHs in the centers of galaxy clusters, and their influence on the cluster gas and galaxy growth, using the next generation of high spectral and spatial resolution X-ray and microwave telescopes.

astro-ph.HE↗

arXiv2019

Astro2020: Hot Drivers of Stellar Feedback from 10 to 10,000 pc

Stellar feedback -- stars regulating further star formation through the injection of energy and momentum into the interstellar medium -- operates through a complex set of processes that originate in star clusters but shape entire galaxies. A mature theory of stellar feedback is essential to a complete theory of star and galaxy formation, but the energy and momentum injected by hot gas into its surroundings remains unclear. With a next-generation X-ray observatory, breakthrough progress can be made through precision measurements of the temperature, density, velocity, and abundances of hot gas on scales of star clusters to galactic superwinds.

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arXiv2019

Astro2020: How does dust escape from galaxies?

Whenever gas is blown out of a galaxy, chances are that it contains some cosmic dust. This dust is an important part of the metals budget for the circumgalactic and intergalactic media, and traces the outflow and stripping history of the galaxy. The dust is also interesting in its own right, as dust plays an essential role in many astrophysical processes. We have only begun to learn about circumgalactic dust, and in particular we do not know how (and when) it escapes its host galaxy. Here we describe the prospects for measuring the dust mass and properties around many individual galaxies, which will form the basis for understanding how the dust got there.

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