arXiv subjects

Sylvain Veilleux

Publications and source records attributed to Sylvain Veilleux.

At least 163 records · Page 9Linked to original sources

arXiv2011

Chandra Discovery of a Binary Active Galactic Nucleus in Mrk 739

We have discovered a binary AGN in the galaxy Mrk 739 using Chandra and Swift BAT. We find two luminous L_2-10 keV=1.1*10^43 and 1.0*10^42 erg/s, unresolved nuclei with a projected separation of 3.4 kpc (5.8\pm0.1) coincident with two bulge components in the optical image. The western X-ray source (Mrk 739W) is highly variable (2.5x) during the 4-hour Chandra observation and has a very hard spectrum consistent with an AGN. While the eastern component was already known to be an AGN based on the presence of broad optical recombination lines, Mrk 739W shows no evidence of being an AGN in optical, UV, and radio observations, suggesting the critical importance of high spatial resolution hard X-ray observations (>2 keV) in finding these binary AGN. A high level of star formation combined with a very low L_[O III]/L_2-10 keV ratio cause the AGN to be missed in optical observations. CO observations of the (3-2) and (2-1) lines indicate large amounts of molecular gas in the system that could be driven towards the black holes during the violent galaxy collision and be key to fueling the binary AGN. Mrk 739E has a high Eddington ratio of 0.71 and a small black hole (log M_BH=7.05\pm0.3) consistent with an efficiently accreting AGN. Other than NGC 6240, this stands as the nearest case of a binary AGN discovered to date.

astro-ph.CO↗

arXiv2011

Host Galaxy Properties of the Swift BAT Ultra Hard X-ray Selected AGN

We have assembled the largest sample of ultra hard X-ray selected (14-195 keV) AGN with host galaxy optical data to date, with 185 nearby (z<0.05), moderate luminosity AGN from the Swift BAT sample. The BAT AGN host galaxies have intermediate optical colors (u-r and g-r) that are bluer than a comparison sample of inactive galaxies and optically selected AGN from the Sloan Digital Sky Survey (SDSS) which are chosen to have the same stellar mass. Based on morphological classifications from the RC3 and the Galaxy Zoo, the bluer colors of BAT AGN are mainly due to a higher fraction of mergers and massive spirals than in the comparison samples. BAT AGN in massive galaxies (log M_*>10.5) have a 5 to 10 times higher rate of spiral morphologies than in SDSS AGN or inactive galaxies. We also see enhanced far-IR emission in BAT AGN suggestive of higher levels of star formation compared to the comparison samples. BAT AGN are preferentially found in the most massive host galaxies with high concentration indexes indicative of large bulge-to-disk ratios and large supermassive black holes. The narrow-line BAT AGN have similar intrinsic luminosities as the SDSS NL Seyferts based on measurements of [O III]. There is also a correlation between the stellar mass and X-ray emission. The BAT AGN in mergers have bluer colors and greater ultra hard X-ray emission compared to the BAT sample as whole. In agreement with the Unified Model of AGN, and the relatively unbiased nature of the BAT sources, the host galaxy colors and morphologies are independent of measures of obscuration such as X-ray column density or Seyfert type. The high fraction of massive spiral galaxies and galaxy mergers in BAT AGN suggest that host galaxy morphology is related to the activation and fueling of local AGN.

astro-ph.CO↗

arXiv2011

Star Formation Efficiency in the Cool Cores of Galaxy Clusters

We have assembled a sample of high spatial resolution far-UV (Hubble Space Telescope Advanced Camera for Surveys Solar Blind Channel) and Halpha (Maryland-Magellan Tunable Filter) imaging for 15 cool core galaxy clusters. These data provide a detailed view of the thin, extended filaments in the cores of these clusters. Based on the ratio of the far-UV to Halpha luminosity, the UV spectral energy distribution, and the far-UV and Halpha morphology, we conclude that the warm, ionized gas in the cluster cores is photoionized by massive, young stars in all but a few (Abell 1991, Abell 2052, Abell 2580) systems. We show that the extended filaments, when considered separately, appear to be star-forming in the majority of cases, while the nuclei tend to have slightly lower far-UV luminosity for a given Halpha luminosity, suggesting a harder ionization source or higher extinction. We observe a slight offset in the UV/Halpha ratio from the expected value for continuous star formation which can be modeled by assuming intrinsic extinction by modest amounts of dust (E(B-V) ~ 0.2), or a top-heavy IMF in the extended filaments. The measured star formation rates vary from ~ 0.05 Msun/yr in the nuclei of non-cooling systems, consistent with passive, red ellipticals, to ~ 5 Msun/yr in systems with complex, extended, optical filaments. Comparing the estimates of the star formation rate based on UV, Halpha and infrared luminosities to the spectroscopically-determined X-ray cooling rate suggests a star formation efficiency of 14(+18)(-8)%. This value represents the time-averaged fraction, by mass, of gas cooling out of the intracluster medium which turns into stars, and agrees well with the global fraction of baryons in stars required by simulations to reproduce the stellar mass function for galaxies. This result provides a new constraint on the efficiency of star formation in accreting systems.

astro-ph.CO↗

arXiv2011

Integral Field Spectroscopy of Massive, Kiloparsec-Scale Outflows in the Infrared-Luminous QSO Mrk 231

The quasi-stellar object (QSO)/merger Mrk 231 is arguably the nearest and best laboratory for studying QSO feedback. It hosts several outflows, including broad-line winds, radio jets, and a poorly-understood kpc scale outflow. In this Letter, we present integral field spectroscopy from the Gemini telescope that represents the first unambiguous detection of a wide-angle, kpc scale outflow from a powerful QSO. Using neutral gas absorption, we show that the nuclear region hosts an outflow with blueshifted velocities reaching 1100 km/s, extending 2-3 kpc from the nucleus in all directions in the plane of the sky. A radio jet impacts the outflow north of the nucleus, accelerating it to even higher velocities (up to 1400 km/s). Finally, 3.5 kpc south of the nucleus, star formation is simultaneously powering an outflow that reaches more modest velocities of only 570 km/s. Blueshifted ionized gas is also detected around the nucleus at lower velocities and smaller scales. The mass and energy flux from the outflow are >~2.5 times the star formation rate and >~0.7% of the active galactic nucleus luminosity, consistent with negative feedback models of QSOs.

astro-ph.GA↗

arXiv2011

The Effect of Environment on the Formation of Halpha Filaments and Cool Cores in Galaxy Groups and Clusters

We present the results of a combined X-ray and Halpha study of 10 galaxy groups and 17 galaxy clusters using the Chandra X-ray Observatory and the Maryland Magellan Tunable Filter. We find no difference in the morphology or detection frequency of Halpha filaments in groups versus clusters, over the mass range 10^13 < M_500 < 10^15 Msun. The detection frequency of Halpha emission is shown to be only weakly dependent on the total mass of the system, at the 52% confidence level. In contrast, we find that the presence of Halpha filaments is strongly correlated with both the global (89% confidence level) and core (84%) ICM entropy, as well as the X-ray cooling rate (72%). The Halpha filaments are therefore an excellent proxy for the cooling ICM. The Halpha filaments are more strongly correlated with the cooling properties of the ICM than with the radio properties of the BCG; this further supports the scenario where these filaments are directly associated with a thermally-unstable, rapidly cooling ICM, rather than radio bubbles. The ICM cooling efficiency, defined as the X-ray cooling rate per unit gas mass, is shown to correlate with the total system mass, indicating that groups are more efficient at cooling than clusters. This result implies that, in systems with cool cores, AGN feedback scales with the total mass of the system, in agreement with earlier suggestions.

astro-ph.HE↗

arXiv2011

Identification of a Complete 160 micron Flux-Limited Sample of Infrared Galaxies in the ISO Lockman Hole 1-Deg^2 Deep Fields: Source Properties and Evidence for Strong Evolution in the FIR Luminosity Function for ULIRGs

We have identified a complete, flux-limited, (S_160>120 mJy), sample of 160 micron-selected sources from Spitzer observations of the 1-deg^2 ISO Deep Field region in the Lockman Hole. Ground-based UV, optical and near-infrared (NIR) photometry and optical spectroscopy have been used to determine colors, redshifts and masses for the complete sample of 40 galaxies. Spitzer-IRAC+MIPS photometry, supplemented by ISOPHOT data at 90 micron and 170 micron, has been used to calculate accurate total infrared luminosities, LIR(8-1000 micron), and to determine the IR luminosity function (LF) of luminous infrared galaxies (LIRGs). The maximum observed redshift is z~0.80 and the maximum total infrared luminosity is log(L_IR/L_Sun)=12.74. Over the luminosity range log(L_IR/L_Sun)=10-12, the LF for LIRGs in the Lockman Hole Deep Field is similar to that found previously for local sources at similar infrared luminosities. The mean host galaxy mass, log(M/M_Sun)=10.7, and dominance of HII-region spectral types, is also similar to what has been found for local LIRGs, suggesting that intense starbursts likely power the bulk of the infrared luminosity for sources in this range of LIR. However for the most luminous sources, log(L_IR/L_Sun)>12.0, we find evidence for strong evolution in the LF \propto (1+z)6\pm1, assuming pure number density evolution. These ultraluminous infrared galaxies (ULIRGs) have a larger mean host mass, log(M/M_Sun)=11.0, and exhibit disturbed morphologies consistent with strong-interactions/mergers, and they are also more likely to be characterized by starburst-AGN composite or AGN spectral types.

astro-ph.CO↗

arXiv2010

X-QUEST: A Comprehensive X-ray Study of Local ULIRGs and QSOs

We present results from the X-ray portion of a multi-wavelength study of local ULIRGs and QSOs called QUEST (Quasar-ULIRG Evolution STudy). The data consist of new and archival X-ray data on 40 ULIRGs and 26 PG QSOs taken with Chandra and XMM-Newton. A combination of traditional and hardness ratio spectral fitting methods is used to characterize the X-ray properties of these objects. The absorption-corrected 2-10 keV to bolometric luminosity ratios of the ULIRGs and PG QSOs suggest that the likelihood for dominant nuclear activity increases along the merger sequence from "cool" ULIRGs, "warm" ULIRGs, infrared-bright QSOs, and infrared-faint QSOs. The starburst dominates the total power in ULIRGs prior to the merger, and this is followed by rapid black hole growth during and after coalescence. These results are in general agreement with those obtained in the mid-infrared with Spitzer and recent numerical simulations.

astro-ph.GA↗

arXiv2010

The Luminosity Function of Lyman alpha Emitters at Redshift z=7.7

Lyman alpha (Lya) emission lines should be attenuated in a neutral intergalactic medium (IGM). Therefore the visibility of Lya emitters at high redshifts can serve as a valuable probe of reionization at about the 50% level. We present an imaging search for z=7.7 Lya emitting galaxies using an ultra-narrowband filter (filter width= 9A) on the NEWFIRM imager at the Kitt Peak National Observatory. We found four candidate Lya emitters in a survey volume of 1.4 x 10^4 Mpc^3, with a line flux brighter than 6x10^-18 erg/cm^2/s (5 sigma in 2" aperture). We also performed a detailed Monte-Carlo simulation incorporating the instrumental effects to estimate the expected number of Lya emitters in our survey, and found that we should expect to detect one Lya emitter, assuming a non-evolving Lya luminosity function (LF) between z=6.5 and z=7.7. Even if one of the present candidates is spectroscopically confirmed as a z~8 Lya emitter, it would indicate that there is no significant evolution of the Lya LF from z=3.1 to z~8. While firm conclusions would need both spectroscopic confirmations and larger surveys to boost the number counts of galaxies, we successfully demonstrate the feasibility of sensitive near-infrared (1.06 um) narrow-band searches using custom filters designed to avoid the OH emission lines that make up most of the sky background.

astro-ph.CO↗

arXiv2010

On the Origin of the Extended Halpha Filaments in Cooling Flow Clusters

We present a high spatial resolution Halpha survey of 23 cooling flow clusters using the Maryland Magellan Tunable Filter (MMTF), covering 1-2 orders of magnitude in cooling rate, dM/dt, temperature and entropy. We find 8/23 (35%) of our clusters have complex, filamentary morphologies at Halpha, while an additional 7/23 (30%) have marginally extended or nuclear Halpha emission, in general agreement with previous studies of line emission in cooling flow cluster BCGs. A weak correlation between the integrated near-UV luminosity and the Halpha luminosity is also found for our complete sample, with a large amount of scatter about the expected relation for photoionization by young stars. We detect Halpha emission out to the X-ray cooling radius, but no further, in several clusters and find a strong correlation between the Halpha luminosity contained in filaments and the X-ray cooling flow rate of the cluster, suggesting that the warm ionized gas is linked to the cooling flow. Furthermore, we detect a strong enhancement in the cooling properties of the ICM coincident with the Halpha emission, compared to the surrounding ICM at the same radius. While the filaments in a few clusters may be entrained by buoyant radio bubbles, in general, the radially-infalling cooling flow model provides a better explanation for the observed trends. The correlation of the Halpha and X-ray properties suggests that conduction may be important in keeping the filaments ionized. The thinness of the filaments suggests that magnetic fields are an important part of channeling the gas and shielding it from the surrounding hot ICM.

astro-ph.HE↗

arXiv2010

Merging and Clustering of the Swift BAT AGN Sample

We discuss the merger rate, close galaxy environment, and clustering on scales up to a Mpc of the SWIFT BAT hard X-ray sample of nearby (z<0.05), moderate-luminosity active galactic nuclei (AGN). We find a higher incidence of galaxies with signs of disruption compared to a matched control sample (18% versus 1%) and of close pairs within 30 kpc (24% versus 1%). We also find a larger fraction with companions compared to normal galaxies and optical emission line selected AGN at scales up to 250 kpc. We hypothesize that these merging AGN may not be identified using optical emission line diagnostics because of optical extinction and dilution by star formation. In support of this hypothesis, in merging systems we find a higher hard X-ray to [OIII] flux ratio, as well as emission line diagnostics characteristic of composite or star-forming galaxies, and a larger IRAS 60 um to stellar mass ratio.

astro-ph.CO↗

arXiv2010

The Great Observatories All-Sky LIRG Survey: Comparison of Ultraviolet and Far-Infrared Properties

The Great Observatories All-sky LIRG Survey (GOALS) consists of a complete sample of 202 Luminous Infrared Galaxies (LIRGs) selected from the IRAS Revised Bright Galaxy Sample (RBGS). The galaxies span the full range of interaction stages, from isolated galaxies to interacting pairs to late stage mergers. We present a comparison of the UV and infrared properties of 135 galaxies in GOALS observed by GALEX and Spitzer. For interacting galaxies with separations greater than the resolution of GALEX and Spitzer (2-6"), we assess the UV and IR properties of each galaxy individually. The contribution of the FUV to the measured SFR ranges from 0.2% to 17.9%, with a median of 2.8% and a mean of 4.0 +/- 0.4%. The specific star formation rate of the GOALS sample is extremely high, with a median value (3.9*10^{-10} yr^{-1}) that is comparable to the highest specific star formation rates seen in the Spitzer Infrared Nearby Galaxies Survey sample. We examine the position of each galaxy on the IR excess-UV slope (IRX-beta) diagram as a function of galaxy properties, including IR luminosity and interaction stage. The LIRGs on average have greater IR excesses than would be expected based on their UV colors if they obeyed the same relations as starbursts with L_IR < 10^{11}L_0 or normal late-type galaxies. The ratio of L_IR to the value one would estimate from the IRXg-beta relation published for lower luminosity starburst galaxies ranges from 0.2 to 68, with a median value of 2.7. A minimum of 19% of the total IR luminosity in the RBGS is produced in LIRGs and ULIRGs with red UV colors (beta > 0). Among resolved interacting systems, 32% contain one galaxy which dominates the IR emission while the companion dominates the UV emission. Only 21% of the resolved systems contain a single galaxy which dominates both wavelengths.

astro-ph.GA↗

arXiv2010

MMTF-Halpha and HST-FUV Imaging of the Filamentary Complex in Abell 1795

We have obtained deep, high spatial resolution images of the central region of Abell 1795 at Halpha and [NII] (6583A) with the Maryland Magellan Tunable Filter (MMTF), and in the far-ultraviolet (FUV) with the Advanced Camera for Surveys Solar Blind Channel on the Hubble Space Telescope (HST). The superb image quality of the MMTF data has made it possible to resolve the known SE filament into a pair of thin, intertwined filaments extending for ~50 kpc, with a width < 1 kpc. The presence of these thin, tangled strands is suggestive of a cooling wake where runaway cooling is taking place, perhaps aided by an enhanced magnetic field in this region. The HST data further resolve these strands into chains of FUV-bright stellar clusters, indicating that these filaments are indeed sites of on-going star formation, but at a rate ~2 orders of magnitude smaller than the mass-deposition rates predicted from the X-ray data. The elevated [NII]/Halpha ratio and large spatial variations of the FUV/Halpha flux ratio across the filaments indicate that O-star photoionization is not solely responsible for the ionization. The data favor collisional heating by cosmic rays either produced in-situ by magnetohydrodynamical processes or conducted in from the surrounding intracluster medium.

astro-ph.CO↗

arXiv2009

Neutral Gas Outflows and Inflows in Infrared-Faint Seyfert Galaxies

Previous studies of the Na I D interstellar absorption line doublet have shown that galactic winds occur in most galaxies with high infrared luminosities. However, in infrared-bright composite systems where a starburst coexists with an active galactic nucleus (AGN), it is unclear whether the starburst, the AGN, or both are driving the outflows. The present paper describes the results from a search for outflows in 35 infrared-faint Seyferts with 10^9.9 < L_IR/L_sun < 10^11, or, equivalently, star formation rates (SFR) of ~0.4 -- 9 solar masses per year, to attempt to isolate the source of the outflow. We find that the outflow detection rates for the infrared-faint Seyfert 1s (6%) and Seyfert 2s (18%) are lower than previously reported for infrared-luminous Seyfert 1s (50%) and Seyfert 2s (45%). The outflow kinematics of infrared-faint and infrared-bright Seyfert 2 galaxies resemble those of starburst galaxies, while the outflow velocities in Seyfert 1 galaxies are significantly larger. Taken together, these results suggest that the AGN does not play a significant role in driving the outflows in most infrared-faint and infrared-bright systems, except the high-velocity outflows seen in Seyfert 1 galaxies. Another striking result of this study is the high rate of detection of inflows in infrared-faint galaxies (39% of Seyfert 1s, 35% of Seyfert 2s), significantly larger than in infrared-luminous Seyferts (15%). This inflow may be contributing to the feeding of the AGN in these galaxies, and potentially provides more than enough material to power the observed nuclear activity over typical AGN lifetimes.

astro-ph.GA↗

arXiv2009

Optical Spectral Properties of Swift BAT Hard X-ray Selected Active Galactic Nuclei Sources

The Swift Burst Alert Telescope (BAT) survey of Active Galactic Nuclei (AGN) is providing an unprecedented view of local AGNs ( = 0.03) and their host galaxy properties. In this paper, we present an analysis of the optical spectra of a sample of 64 AGNs from the 9-month survey, detected solely based on their 14-195 keV flux. Our analysis includes both archived spectra from the Sloan Digital Sky Survey and our own observations from the 2.1-m Kitt Peak National Observatory telescope. Among our results, we include line ratio classifications utilizing standard emission line diagnostic plots, [O III] 5007 A luminosities, and H-beta derived black hole masses. As in our X-ray study, we find the type 2 sources to be less luminous (in [O III] 5007 A and 14-195 keV luminosities) with lower accretion rates than the type 1 sources. We find that the optically classified LINERs, H II/composite galaxies, and ambiguous sources have the lowest luminosities, while both broad line and narrow line Seyferts have similar luminosities. From a comparison of the hard X-ray (14-195 keV) and [O III] luminosities, we find that both the observed and extinction-corrected [O III] luminosities are weakly correlated with X-ray luminosity. In a study of the host galaxy properties from both continuum fits and measurements of the stellar absorption indices, we find that the hosts of the narrow line sources have properties consistent with late type galaxies.

astro-ph.CO↗

arXiv2009

The Maryland-NOAO Instrument Partnership (2003-2009)

Seven years ago, with the encouragement of the NSF and AURA, NOAO requested proposals from the community to partner with the national observatory to improve instrumentation and/or telescope capabilities at KPNO and CTIO. Of the proposals that were selected, one came from the University of Maryland with the goals of helping NOAO complete the development, construction, and deployment of a new, wide-field, near-IR imager (NEWFIRM) and of working with NOAO to develop data reduction pipelines and data archiving capabilities at NOAO. By all measures, the Maryland-NOAO instrument partnership has been a resounding success. In this article, we briefly describe the positive impact this partnership has had on Maryland, NOAO, and the astronomical community.

astro-ph.IM↗

arXiv2008

Suzaku Observations of Local Ultraluminous Infrared Galaxies

We report the results from our analysis of {\it Suzaku} XIS (0.5-10 keV) and HXD/PIN (15-40 keV) observations of five well-known local ULIRGs: {\em IRAS} F05189-2524, {\em IRAS} F08572+3915, Mrk 273, PKS 1345+12, and Arp 220. The XIS observations of F05189-2524 and Mrk 273 reveal strong iron lines consistent with Fe K$α$ and changes in spectral shapes with respect to previous {\it Chandra} and {\it XMM-Newton} observations. Mrk 273 is also detected by the HXD/PIN at $\sim$1.8-$σ$. For F05189-2524, modeling of the data from the different epochs suggests that the change in spectral shape is likely due to the central source switching off, leaving behind a residual reflection spectrum, or an increase in the absorbing column. An increase in the covering fraction of the absorber can describe the spectral variations seen in Mrk 273, although a reduction in the intrinsic AGN luminosity cannot be formally ruled out. The {\it Suzaku} spectra of Mrk 273 are well fit by a ~94% covering fraction model with a column density of $\sim10^{24}$ cm$^{-2}$. The absorption-corrected log[$L_{\rm 2-10 keV}$ / $L_{\rm IR}$] ratio is consistent with those found in PG Quasars. The 0.5-10 keV spectrum of PKS 1345+12 and Arp 220 seem unchanged from previous observations and their hard X-ray emission is not convincingly detected by the HXD/PIN. The large column density derived from CO observations and the large equivalent width of an ionized Fe line in Arp 220 can be reconciled by an ionized reflection model. F08572+3915 is undetected in both the XIS and HXD/PIN, but the analysis of unpublished {\em Chandra} data provides a new measurement at low energies.

astro-ph↗

arXiv2008

AGN Host Galaxies

In this series of four lectures, I discuss four important aspects of AGN host galaxies. In Lecture #1, I address the starburst-AGN connection. First, I briefly review the primary diagnostic tools that are used to quantify and distinguish star formation and nuclear activity. Next I describe the best evidence for a connection between these two processes, first at low luminosity and then at high luminosity. In the last section, I summarize the main results and offer possible explanations. In Lecture #2, I discuss our current understanding of ultraluminous infrared galaxies. First, I describe the general properties of ULIRGs, comparing the local sample with their distant counterparts. Then I discuss the role of ULIRGs in the formation and evolution of spheroids and their massive black holes. The discussion of their possible role in the metal enrichment of the IGM through superwinds is postponed until Lecture #3. In this third lecture, I discuss the importance of feedback processes in the local and distant universe. The emphasis is on mechanical feedback. I describe the basic physics of winds, a few classic examples of winds in the local universe, the statistical properties of winds, near and far, and their impact on galaxy formation and evolution. A list of potential thesis projects is given at the end. The fourth and final lecture is on elemental abundances as tracers of star formation. First, I explain the basic principles behind chemical evolution, and describe three simple models whose predictions are compared with observations in the Milky Way. Next I discuss and give an interpretation of the results of abundance determinations in local quiescent and starburst galaxies before discussing elemental abundances in the more distant universe.

astro-ph↗

arXiv2007

A Connection between Star Formation in Nuclear Rings and their Host Galaxies

We present results from a photometric H-alpha survey of 22 nuclear rings, aiming to provide insight into their star formation properties, including age distribution, dynamical timescales, star formation rates, and galactic bar influence. We find a clear relationship between the position angles and ellipticities of the rings and those of their host galaxies, which indicates the rings are in the same plane as the disk and circular. We use population synthesis models to estimate ages of each H-alpha emitting HII region, which range from 1 Myr to 10 Myrs throughout the rings. We find that approximately half of the rings contain azimuthal age gradients that encompass at least 25% of the ring, although there is no apparent relationship between the presence or absence of age gradients and the morphology of the rings or their host galaxies. NGC1343, NGC1530, and NGC4321 show clear bipolar age gradients, where the youngest HII regions are located near the two contact points of the bar and ring. We speculate in these cases that the gradients are related to an increased mass inflow rate and/or an overall higher gas density in the ring, which would allow for massive star formation to occur on short timescales, after which the galactic rotation would transport the HII regions around the ring as they age. Two-thirds of the barred galaxies show correlation between the locations of the youngest HII region(s) in the ring and the location of the contact points, which is consistent with predictions from numerical modeling.

astro-ph↗