arXiv subjects

M. Elvis

Publications and source records attributed to M. Elvis.

At least 55 records · Page 3Linked to original sources

arXiv2019

Quantifying Feedback from Narrow Line Region Outflows in Nearby Active Galaxies. II. Spatially Resolved Mass Outflow Rates for the QSO2 Markarian 34

We present spatially resolved mass outflow rate measurements ($\dot M_{out}$) for the narrow line region of Markarian 34, the nearest Compton-thick type 2 quasar (QSO2). Spectra obtained with the Hubble Space Telescope and at Apache Point Observatory reveal complex kinematics, with distinct signatures of outflow and rotation within 2 kpc of the nucleus. Using multi-component photoionization models, we find that the outflow contains a total ionized gas mass of $M \approx 1.6 \times 10^6 M_{\odot}$. Combining this with the kinematics yields a peak outflow rate of $\dot M_{out} \approx 2.0 \pm 0.4~M_{\odot}$ yr$^{-1}$ at a distance of 470 pc from the nucleus, with a spatially integrated kinetic energy of $E \approx 1.4 \times 10^{55}$ erg. These outflows are more energetic than those observed in Mrk 573 and NGC 4151, supporting a correlation between luminosity and outflow strength even though they have similar peak outflow rates. The mix of rotational and outflowing components suggests that spatially resolved observations are required to determine accurate outflow parameters in systems with complex kinematics. (See appended erratum for updated values.)

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arXiv2019

OWL-MOON : Very high resolution spectro-imaging and Earth-Moon interferometry: exoplanets to cosmology

We address three major questions in astronomy, namely the detection of biosignatures on habitable exoplanets, the geophysics of exoplanets and cosmology. To achieve this goal, two requirements are needed. First a very large aperture to detect spectro-polarimetric and spatial features of faint objects such as exoplanets, and second a continuous monitoring to characterize the temporal behavior of exoplanets such as rotation period, meteorology and seasons. An Earth-based telescope is not suited for continuous monitoring and the atmosphere limits the ultimate angular resolution and spectro-polarimetrical domain. Moreover, a space telescope in orbit is limited in aperture, to perhaps 15 m over the next several decades. This is why we propose an OWL-class lunar telescope with a 50-100 m aperture for visible and infrared (IR) astronomy, based on ESO's Overwhelmingly Large Telescope concept, unachievable on Earth for technical issues such as wind stress that are not relevant for a lunar platform. It will be installed near the south pole of the Moon to allow continuous target monitoring. The low gravity of the Moon will facilitate its building and manoeuvring, compared to Earth-based telescopes. As a guaranteed by-product, such a large lunar telescope will allow Intensity Interferometric measurements when coupled with large Earth-based telescopes, leading to pico-second angular resolution.

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arXiv2019

X-ray Photons in the CO 2-1 'Lacuna' of NGC 2110

A recent ALMA study of the Seyfert 2 Active Galactic Nucleus (AGN) NGC 2110 by Rosario et al. (2019) has reported a remarkable lack of CO 2-1 emission from the circumnuclear region, where optical lines and H2 emission are observed, leading to the suggestion of excitation of the molecular clouds by the AGN. Since interaction with X-ray photons could be the cause of this excitation, we have searched the archival Chandra data for corroborating evidence. We report an extra-nuclear ~1'' (~170 pc) feature found in the soft (<1.0 keV) Chandra data of the Seyfert 2 Active Galactic Nucleus (AGN) NGC 2110. This feature is elongated to the north of the nucleus and its shape matches well that of the optical lines and H2 emission observed in this region, which is devoid of CO 2-1 emission. The Chandra image completes the emerging picture of a multi-phase circumnuclear medium excited by the X-rays from the AGN, with dense warm molecular clouds emitting in H2 but depleted of CO 2-1 emission.

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arXiv2019

Multiphase gas flows in the nearby Seyfert galaxy ESO428-G14

We present ALMA rest-frame 230 GHz continuum and CO(2-1) line observations of the nearby Compton-thick Seyfert galaxy ESO428-G14, with angular resolution 0.7 arcsec (78 pc). We detect CO(2-1) emission from spiral arms and a circum-nuclear ring with 200 pc radius, and from a transverse gas lane with size of $\sim100$ pc, which crosses the nucleus and connects the two portions the circumnuclear ring. The molecular gas in the host galaxy is distributed in a rotating disk with intrinsic circular velocity $v_{rot}=135$ km/s, inclination $i=57$ deg, and dynamical mass $M_{dyn }=5\times 10^9~\rm M_{\odot}$ within a radius of $\sim 1$ kpc. In the inner 100 pc region CO is distributed in a equatorial bar, whose kinematics is highly perturbed and consistent with an inflow of gas towards the AGN. This inner CO bar overlaps with the most obscured, Compton-thick region seen in X-rays. We derive a column density of $\rm N(H_2) \approx 2\times10^{23}~ cm^{-2}$ in this region, suggesting that molecular gas may contribute significantly to the AGN obscuration. We detect a molecular outflow with a total outflow rate $\rm \dot M_{of}\approx 0.8~M_{\odot}/yr$, distributed along a bi-conical structure with size of $700$ pc on both sides of the AGN. The bi-conical outflow is also detected in the $\rm H_2$ emission line at 2.12 $μ$m, which traces a warmer nuclear outflow located within 170 pc from the AGN. This suggests that the outflow cools with increasing distance from the AGN. We find that the hard X-ray emitting nuclear region mapped with Chandra is CO-deprived, but filled with warm molecular gas traced by $\rm H_2$ - thus confirming that the hard (3-6 keV) continuum and Fe K$α$ emission are due to scattering from dense neutral clouds in the ISM.

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arXiv2019

Increasing the Discovery Space in Astrophysics - A Collation of Six Submitted White Papers

We write in response to the call from the 2020 Decadal Survey to submit white papers illustrating the most pressing scientific questions in astrophysics for the coming decade. We propose exploration as the central question for the Decadal Committee's discussions.The history of astronomy shows that paradigm changing discoveries are not driven by well formulated scientific questions, based on the knowledge of the time. They were instead the result of the increase in discovery space fostered by new telescopes and instruments. An additional tool for increasing the discovery space is provided by the analysis and mining of the increasingly larger amount of archival data available to astronomers. Revolutionary observing facilities, and the state of the art astronomy archives needed to support these facilities, will open up the universe to new discovery. Here we focus on exploration for compact objects and multi messenger science. This white paper includes science examples of the power of the discovery approach, encompassing all the areas of astrophysics covered by the 2020 Decadal Survey.

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arXiv2018

Chandra Detection of the Circumnuclear Molecular Torus of the Compton Thick AGN in NGC 5643

We report a clumpy elongated feature found with deep Chandra ACIS high-resolution imaging of the Fe Kα line emission in the nuclear region of the Compton Thick Active Galactic Nucleus (CT AGN) galaxy NGC 5643. This feature extends for ~65 pc N-S. No corresponding feature is seen in the 3.0-6.0 keV continuum. The Fe Kα feature is spatially consistent with the N-S elongation found in the CO(2-1) high resolution imaging with ALMA (Alonso-Herrero et al 2018), but slightly more extended than the rotating molecular disk of r=26 pc indicated by the kinematics of the CO(2-1) line. The Chandra detection of a corresponding N-S structure in the neutral Fe Kα line, would argue for both CO and Fe Kα emission originating from the obscuring torus.

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arXiv2018

Deep Chandra Observations of ESO 428-G014: IV. The Morphology of the Nuclear Region in the Hard Continuum and Fe Kα Line

We report the results of high-resolution subpixel imaging of the hard continuum and Fe Kα line of the Compton Thick (CT) Active Galactic Nucleus (AGN) ESO 428-G014, observed with Chandra ACIS. While the 3-4 keV emission is dominated by an extended component, a single nuclear point source is prominent in the 4-6 keV range. Instead, two peaks of similar intensity, separated by ~36 pc in projection on the plane of the sky are detected in the Fe Kα emission. The SE knot could be marginally associated with the heavily obscured hard continuum source. We discuss four possible interpretations of the nuclear morphology. (1) Given the bolometric luminosity and likely black hole (BH) mass of ESO 428-G014, we may be imaging two clumps of the CT obscuring torus in the Fe Kα line. (2) The Fe Kα knots may be connected with the fluorescent emission from the dusty bicone, or (3) with the light echo of a nuclear outburst. (4) We also explore the less likely possibility that we may be detecting the rare signature of merging nuclei. Considering the large-scale kpc-size extent of the hard continuum and Fe Kα emission (Papers I and II), we conclude that the AGN in ESO 428-G014 has been active for at least 104 yrs. Comparison with the models of Czerny et al (2009) suggests high accretion rates during this activity.

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arXiv2018

Deep Chandra Observations of ESO 428-G014: III. High Resolution Spectral Imaging of the Ionization Cone and Radio Jet Region

We have analyzed the deep Chandra observation (~155 ks) of the Compton Thick Active Galactic Nucleus (CT AGN) ESO 428-G014, to study in detail the morphology of the diffuse X-ray emission in the inner ~500 pc radius region. Comparing different X-ray energy bands we find localized differences in the absorbing column and in the emission processes. Collisional ionization may be prevalent in the area of most intense optical line emission (Halpha and [OIII]). There is a good correspondence between optical line, radio continuum and soft (<3 keV) X-ray features, consistent with simulations of jet/molecular disk interactions. At all energies >3 keV, the extended emission in the central 1".5 (170 pc) radius circumnuclear region amounts to ~70-30% of the contribution of a point source in that area (or 40-25% of the total counts in the region). Within a 5" radius, the contribution from extended emission overcomes that from a nuclear point source in the 3-4 keV band. This extended emission suggests scattering of nuclear photons by dense molecular clouds in the inner galactic disk of ESO 428-G014. Its presence may adversely bias the torus modeling of spectra from X-ray telescopes with inferior angular resolution than Chandra, such as NuSTAR and XMM-Newton.

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arXiv2018

Observations of the MIssing Baryons in the warm-hot intergalactic medium

It has been known for decades that the observed number of baryons in the local universe falls about 30-40% short of the total number of baryons predicted by Big-Bang Nucleosynthesis, as inferred from density fluctuations of the Cosmic Microwave Background and seen during the first 2-3 billion years of the universe in the so called Lyman-alpha Forest. A theoretical solution to this paradox locates the missing baryons in the hot and tenuous filamentary gas between galaxies, known as the warm-hot intergalactic medium. However, it is difficult to detect them there because the largest by far constituent of this gas - hydrogen - is mostly ionized and therefore almost invisible in far-ultraviolet spectra with typical signal-to-noise ratios. Indeed, despite the large observational efforts, only a few marginal claims of detection have been made so far. Here we report observations of two absorbers of highly ionized oxygen (OVII) in the high signal-to-noise-ratio X-ray spectrum of a quasar at redshift >0.4. These absorbers show no variability over a 2-year timescale and have no associated cold absorption, making the assumption that they originate from the quasar's intrinsic outflow or the host galaxy's interstellar medium implausible. The OVII systems lie in regions characterized by large (x4 compared to average) galaxy over-densities and their number (down to the sensitivity threshold of our data), agrees well with numerical simulation predictions for the long-sought warm-hot intergalactic medium (WHIM). We conclude that the missing baryons have been found.

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arXiv2018

Deep Chandra Observations of ESO 428-G014: II. Spectral Properties and Morphology of the Large-Scale Extended X-ray Emission

We present a deep Chandra spectral and spatial study of the kpc-scale diffuse X-ray emission of the Compton thick (CT) AGN ESO428-G014. The entire spectrum is best fit with composite photoionization + thermal models. The diffuse emission is more extended at the lower energies (<3 keV). The smaller extent of the hard continuum and Fe Kα profiles imply that the optically thicker clouds responsible for this scattering may be relatively more prevalent closer to the nucleus. These clouds must not prevent soft ionizing X-rays from the AGN escaping to larger radii, in order to have photoionized ISM at larger radii. This suggests that at smaller radii there may be a larger population of molecular clouds to scatter the hard X-rays, as in the Milky Way. The diffuse emission is also significantly extended in the cross-cone direction, where the AGN emission would be mostly obscured by the torus in the standard AGN model. Our results suggest that the transmission of the obscuring region in the cross-cone direction is ~10% than in the cone-direction. In the 0.3-1.5 keV band, the ratio of cross-cone to cone photons increases to ~84\%, suggesting an additional soft diffuse emission component, disjoint from the AGN. This could be due to hot ISM trapped in the potential of the galaxy. The luminosity of this component ~5 10^38 erg s^-1 is roughly consistent with the thermal component suggested by the spectral fits in the 170-900 pc annulus.

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arXiv2018

Hubble Space Telescope Observations of Extended [O III] λ5007 Emission in Nearby QSO2s: New Constraints On AGN / Host Galaxy Interaction

We present a Hubble Space Telescope (HST) survey of extended [O III] λ5007 emission for a sample of 12 nearby (z < 0.12), luminous Type 2 quasars (QSO2s), which we use to measure the extent and kinematics of their AGN-ionized gas. We find the size of the observed [O III] regions scale with luminosity in comparison to nearby, less luminous Seyfert galaxies and radially outflowing kinematics to exist in all targets. We report an average maximum outflow radius of $\sim$600 pc, with gas continuing to be kinematically influenced by the central AGN out to an average radius of $\sim$1130 pc. These findings question the effectiveness of AGN being capable of clearing material from their host bulge in the nearby universe and suggest that disruption of gas by AGN activity may prevent star formation without requiring evacuation. Additionally, we find a dichotomy in our targets when comparing [O III] radial extent and nuclear FWHM, where QSO2s with compact [O III] morphologies typically possess broader nuclear emission-lines.

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arXiv2018

Outflows in the Narrow Line Region of Bright Seyfert Galaxies - I: GMOS-IFU Data

We present two-dimensional maps of emission-line fluxes and kinematics, as well as of the stellar kinematics of the central few kpc of five bright nearby Seyfert galaxies -- Mrk\,6, Mrk\,79, Mrk\,348, Mrk\,607 and Mrk\,1058 -- obtained from observations with the Gemini Multi-Object Spectrograph (GMOS) Integral Field Unit (IFU) on the Gemini North Telescope. The data cover the inner 3\farcs5$\times$5\farcs0 -- corresponding to physical scales in the range 0.6$\times$0.9 to 1.5$\times$2.2\,kpc$^2$ -- at a spatial resolution ranging from 110 to 280 pc with a spectral coverage of 4300 -- 7100\,Å and velocity resolution of $\approx$ 90\,km\,s$^{-1}$. The gas excitation is Seyfert like everywhere but show excitation, but show excitation gradients that are correlated with the gas kinematics, reddening and/or the gas density. The gas kinematics show in all cases two components: a rotation one similar to that observed in the stellar velocity field, and an outflow component. In the case of Mrk607, the gas is counter-rotating relative to the stars. Enhanced gas velocity dispersion is observed in association to the outflows according to two patterns: at the locations of the highest outflow velocities along the ionization axis or perpendicularly to it in a strip centered at the nucleus that we attribute to an equatorial outflow. Bipolar outflows are observed in Mrk\,348 and Mrk\,79, while in Mrk\,1058 only the blueshifted part is clearly observed, while in the cases of Mrk\,6 and Mrk\,607 the geometry of the outflow needs further constraints from modeling to be presented in a forthcoming study, where the mass flow rate and powers will also be obtained.

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arXiv2017

Inferring Compton-thick AGN candidates at z>2 with Chandra using the >8 keV restframe spectral curvature

To fully understand cosmic black hole growth we need to constrain the population of heavily obscured active galactic nuclei (AGN) at the peak of cosmic black hole growth ($z\sim$1-3). Sources with obscuring column densities higher than $\mathrm{10^{24}}$ atoms $\mathrm{cm^{-2}}$, called Compton-thick (CT) AGN, can be identified by excess X-ray emission at $\sim$20-30 keV, called the "Compton hump". We apply the recently developed Spectral Curvature (SC) method to high-redshift AGN (2 5\times 10^{43}}$ erg $\mathrm{s^{-1}}$. In the Cosmological evolution survey (COSMOS), we find an observed CT fraction of $\mathrm{15^{+4}_{-3}\%}$ (40/272) or $\mathrm{32\pm11 \%}$ when corrected for the survey sensitivity. When comparing to low redshift AGN with similar X-ray luminosities, our results imply the CT AGN fraction is consistent with having no redshift evolution. Finally, we provide SC equations that can be used to find high-redshift CT AGN (z>1) for current (XMM-Newton) and future (eROSITA and ATHENA) X-ray missions.

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arXiv2017

The weak neutral Fe fluorescence line and long-term X-ray evolution of the Compton-thick AGN in NGC 7674

We present $NuSTAR$ X-ray observations of the active galactic nucleus (AGN) in NGC 7674. The source shows a flat X-ray spectrum, suggesting that it is obscured by Compton-thick gas columns. Based upon long-term flux dimming, previous work suggested the alternate possibility that the source is a recently switched-off AGN with the observed X-rays being the lagged echo from the torus. Our high-quality data show the source to be reflection-dominated in hard X-rays, but with a relatively weak neutral Fe K$α$ emission line (equivalent width [EW] of $\approx$ 0.4 keV) and a strong Fe XXVI ionised line (EW $\approx$ 0.2 keV). We construct an updated long-term X-ray light curve of NGC 7674 and find that the observed 2-10 keV flux has remained constant for the past $\approx$ 20 years, following a high flux state probed by $Ginga$. Light travel time arguments constrain the minimum radius of the reflector to be $\sim$ 3.2 pc under the switched-off AGN scenario, $\approx$ 30 times larger than the expected dust sublimation radius, rendering this possibility unlikely. A patchy Compton-thick AGN (CTAGN) solution is plausible, requiring a minimum line-of-sight column density ($N_{\rm H}$) of 3 $\times$ 10$^{24}$ cm$^{-2}$ at present, and yields an intrinsic 2-10 keV luminosity of (3-5) $\times$ 10$^{43}$ erg s$^{-1}$. Realistic uncertainties span the range of $\approx$ (1-13) $\times$ 10$^{43}$ erg s$^{-1}$. The source has one of the weakest fluorescence lines amongst {\em bona fide} CTAGN, and is potentially a local analogue of bolometrically luminous systems showing complex neutral and ionised Fe emission. It exemplifies the difficulty of identification and proper characterisation of distant CTAGN based on the strength of the neutral Fe K$α$ line.

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arXiv2017

Observational evidence that positive and negative AGN feedback depends on galaxy mass and jet power

Several studies support the existence of a link between the AGN and star formation activity. Radio jets have been argued to be an ideal mechanism for direct interaction between the AGN and the host galaxy. A drawback of previous surveys of AGN is that they are fundamentally limited by the degeneracy between redshift and luminosity in flux-density limited samples. To overcome this limitation, we present far-infrared Herschel observations of 74 radio-loud quasars (RLQs), 72 radio-quiet quasars (RQQs) and 27 radio galaxies (RGs), selected at 0.9<z<1.1 which span over two decades in optical luminosity. By decoupling luminosity from evolutionary effects, we investigate how the star formation rate (SFR) depends on AGN luminosity, radio-loudness and orientation. We find that: 1) the SFR shows a weak correlation with the bolometric luminosity for all AGN sub-samples, 2) the RLQs show a SFR excess of about a factor of 1.4 compared to the RQQs, matched in terms of black hole mass and bolometric luminosity, suggesting that either positive radio-jet feedback or radio AGN triggering are linked to star-formation triggering and 3) RGs have lower SFRs by a factor of 2.5 than the RLQ sub-sample with the same BH mass and bolometric luminosity. We suggest that there is some jet power threshold at which radio-jet feedback switches from enhancing star formation (by compressing gas) to suppressing it (by ejecting gas). This threshold depends on both galaxy mass and jet power.

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arXiv2017

Discovery of Kiloparsec Extended Hard X-ray Continuum and Fe K alpha from the Compton Thick AGN ESO428-G014

We report the discovery of kpc-scale diffuse emission in both the hard continuum (3-6 keV) and in the Fe K alpha line in the Compton Thick (CT) Seyfert galaxy ESO428-G014. This extended hard component contains at least ~24% of the observed 3-8 keV emission, and follows the direction of the extended optical line emission (ionization cone) and radio jet. The extended hard component has ~0.5% of the intrinsic 2-10 keV luminosity within the bi-cones. A uniform scattering medium of density 1 cm-3 would produce this luminosity in a 1kpc path length in the bi-cones. Alternatively, higher column density molecular clouds in the disk of ESO428-G014 may be responsible for these components. The continuum may also be enhanced by the acceleration of charged particles in the radio jet. The steeper spectrum (Gamma ~1.7 +-0.4) of the hard continuum outside of the central 1.5" radius nuclear region suggests a contribution of scattered/fluorescent intrinsic Seyfert emission. Ultrafast nuclear outflows cannot explain the extended F K alpha emission. This discovery suggests that we may need to revise the picture at the base of our interpretation of CT AGN spectra.

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arXiv2017

Spectral analysis of four 'hypervariable' AGN: a microneedle in the haystack?

We analyze four extreme active galactic nuclei (AGN) transients to explore the possibility that they are caused by rare, high-amplitude microlensing events. These previously unknown type-I AGN are located in the redshift range 0.6-1.1 and show changes of > 1.5 mag in the g-band on a time-scale of ~years. Multi-epoch optical spectroscopy, from the William Herschel Telescope, shows clear differential variability in the broad line fluxes with respect to the continuum changes and also evolution in the line profiles. In two cases, a simple point-source, point-lens microlensing model provides an excellent match to the long-term variability seen in these objects. For both models, the parameter constraints are consistent with the microlensing being due to an intervening stellar mass object but as yet there is no confirmation of the presence of an intervening galaxy. The models predict a peak amplification of 10.3/13.5 and an Einstein time-scale of 7.5/10.8 yr, respectively. In one case, the data also allow constraints on the size of the CIII] emitting region, with some simplifying assumptions, to to be ~1.0-6.5 light-days and a lower limit on the size of the MgII emitting region to be > 9 light-days (half-light radii). This CIII] radius is perhaps surprisingly small. In the remaining two objects, there is spectroscopic evidence for an intervening absorber but the extra structure seen in the light curves requires a more complex lensing scenario to adequately explain.

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arXiv2016

A Decade of WHIM Searches: Where do we Stand and Where do we Go?

In this article we first review the past decade of efforts in detecting the missing baryons in the Warm Hot Intergalactic Medium (WHIM) and summarize the current state of the art by updating the baryon census and physical state of the detected baryons in the local Universe. We then describe observational strategies that should enable a significant step forward in the next decade, while waiting for the step-up in quality offered by future missions. In particular we design a multi-mega-second and multiple cycle XMM-Newton legacy program (which we name the Ultimate Roaming Baryon Exploration, or URBE) aimed to secure detections of the peaks in the density distribution of the Universe missing baryons over their entire predicted range of temperatures.

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