Near-infrared Adaptive Optics Imaging Research Articles

Direct Imaging and Spectroscopy of a Planetary-Mass Candidate Companion to a Young Solar Analog

We present Gemini near-infrared adaptive optics imaging and spectroscopy of a planetary-mass candidate companion to 1RXS J160929.1–210524, a roughly solar-mass member of the 5 Myr old Upper Scorpius association. The object, separated by 2.22 -->'' or 330 AU at ~150 pc, has infrared colors and spectra suggesting a temperature of -->1800−100+200 K, and spectral type of L4 -->−2+1. The H- and K-band spectra provide clear evidence of low surface gravity, and thus youth. Based on the widely used DUSTY models, we infer a mass of -->8−2+4 MJup. If gravitationally bound, this would be the lowest mass companion imaged around a normal star thus far, and its existence at such a large separation would pose a serious challenge to theories of star and planet formation.

Adaptive optics imaging and optical spectroscopy of a multiple merger in a luminous infrared galaxy★

(abridged) We present near-infrared (NIR) adaptive optics imaging obtained with VLT/NACO and optical spectroscopy from the Southern African Large Telescope (SALT) of a luminous infrared galaxy (LIRG) IRAS 19115-2124. These data are combined with archival HST imaging and Spitzer imaging and spectroscopy, allowing us to study this disturbed interacting/merging galaxy, dubbed the Bird, in extraordinary detail. In particular, the data reveal a triple system where the LIRG phenomenon is dominated by the smallest of the components. One nucleus is a regular barred spiral with significant rotation, while another is highly disturbed with a surface brightness distribution intermediate to that of disk and bulge systems, and hints of remaining arm/bar structure. We derive dynamical masses in the range 3-7x10^10 M_solar for both. The third component appears to be a 1-2x10^10 M_solar mass irregular galaxy. The total system exhibits HII galaxy-like optical line ratios and strengths, and no evidence for AGN activity is found from optical or mid-infrared data. The star formation rate is estimated to be 190 M_solar/yr. We search for SNe, super star clusters, and detect 100-300 km/s outflowing gas from the Bird. Overall, the Bird shows kinematic, dynamical, and emission line properties typical for cool ultra luminous IR galaxies. However, the interesting features setting it apart for future studies are its triple merger nature, and the location of its star formation peak - the strongest star formation does not come from the two major K-band nuclei, but from the third irregular component. Aided by simulations, we discuss scenarios where the irregular component is on its first high-speed encounter with the more massive components.

The (quite dark) stellar cluster around the supermassive black hole Sagittarius A* at the center of the Milky Way

AbstractHigh-resolution seeing limited and adaptive optics near-infrared imaging observations of the stellar cluster within about one parsec of the massive black hole Sagittarius A* allow us to obtain a detailed picture of the structure of the nuclear star cluster of the Milky Way. We find that the stellar number counts and the diffuse light of the unresolved stellar population can be described very well by a stellar density function in the form of a broken-power law. This agrees well with theoretical predictions on the structure of a dynamically relaxed star cluster around a massive black hole. However, the cusp slope is found to be too shallow, which may be related to mixing of different stellar populations and continuous star formation, phenomena that are not taken into account by current theory. Mass densities larger than 107 solar masses per pc3 are reached within 0.1 pc of the central black hole. Intriguingly, up to several tens of percent of the total cluster mass in the central parsec may be in the form of dark stellar remnants.

Near‐Infrared Adaptive Optics Imaging of QSO Host Galaxies

We report near-infrared (primarily H band) adaptive optics (AO) imaging with the Gemini-N and Subaru Telescopes, of a representative sample of 32 nearby (z < 0.3) QSOs selected from the Palomar-Green (PG) Bright Quasar Survey (BQS), in order to investigate the properties of the host galaxies. Two-dimensional modeling and visual inspection of the images shows that ~36% of the hosts are ellipticals, ~39% contain a prominent disk component, and ~25% are of undetermined type. Thirty percent show obvious signs of disturbance. The mean MH(host) = -24.82 (2.1L), with a range -23.5 to -26.5 (~0.63L to 10L). At <L, all hosts have a dominant disk component, while at >2L most are ellipticals. "Disturbed" hosts are found at all MH(host), while "strongly disturbed" hosts appear to favor the more luminous hosts. Hosts with prominent disks have less luminous QSOs, while the most luminous QSOs are almost exclusively in ellipticals or in mergers (which presumably shortly will be ellipticals). At z < 0.13, where our sample is complete at B band, we find no clear correlation between MB(QSO) and MH(host). However, at z > 0.15, the more luminous QSOs (MB < -24.7), and four of five of the radio-loud QSOs, have the most luminous H-band hosts (>7L), most of which are ellipticals. Finally, we find a strong correlation between the "infrared excess," LIR/LBB, of QSOs with host type and degree of disturbance. Disturbed and strongly disturbed hosts and hosts with dominant disks have LIR/LBB twice that of nondisturbed and elliptical hosts, respectively. QSOs with disturbed and strongly disturbed hosts are also found to have morphologies and mid/far-infrared colors that are similar to what is found for "warm" ultraluminous infrared galaxies, providing further evidence for a possible evolutionary connection between both classes of objects.

The Central Regions of M31 in the 3-5 μm Wavelength Region

Images obtained with NIRI on the Gemini North telescope are used to investigate the photometric properties of the central regions of M31 in the 3-5 μm wavelength range. The light distribution in the central arcsecond differs from what is seen in the near-infrared in the sense that the difference in peak brightness between P1 and P2 is larger in M' than in K'; no obvious signature of P3 is detected in M'. These results can be explained if there is a source of emission that contributes ~20% of the peak M' light of P1, has an effective temperature of no more than a few hundred K, and is located between P1 and P2. Based on the red K - M' color of this source, it is suggested that the emission originates in a circumstellar dust shell surrounding a single bright asymptotic giant branch (AGB) star. Tests of this hypothesis are described. A bright source that is ~8'' from the center of the galaxy is also detected in M'. This object has red colors and an absolute brightness in M' that is similar to the most highly evolved AGB stars in the solar neighborhood; hence, it is likely to be a very evolved AGB star embedded in a circumstellar envelope. The K-band brightness of this star is close to the peak expected for AGB evolution, and an age of only a few hundred million years is estimated, which is comparable to that of the P3 star cluster. Finally, using high angular resolution near-infrared adaptive optics images as a guide, a sample of unblended AGB stars outside of the central few arcseconds is defined in L'. The (L', K - L') color-magnitude diagram of these sources shows a dominant AGB population with a peak L' brightness and a range of K - L' colors that are similar to those of the most luminous M giants in the Galactic bulge.

Subaru Near Infrared Coronagraphic Images of T Tauri

Abstract High angular resolution near-infrared (JHK) adaptive optics images of T Tau were obtained with the infrared camera Coronagraphic Imager with Adaptive Optics (CIAO) mounted on the 8.2 m Subaru Telescope in 2002 and 2004. The images resolve a complex circumstellar structure around a multiple system. We resolved T Tau Sa and Sb as well as T Tau N and S. The estimated orbit of T Tau Sb indicates that it is probably bound to T Tau Sa. The $K$ band flux of T Tau S decreased by $\sim 1.7 \,\mathrm{Jy}$ in 2002 November compared with that in 2001 mainly because T Tau Sa became fainter. The arc-like ridge detected in our near-infrared images is consistent with what is seen at visible wavelengths, supporting the interpretation in previous studies that the arc is part of the cavity wall seen relatively pole-on. Halo emission is detected out to $\sim 2^{\prime\prime}$ from T Tau N. This may be light scattered off the common envelope surrounding the T Tauri multiple system.

Near-Infrared Images of Protoplanetary Disk Surrounding HD 142527

We discovered a unique morphology in a disk around the Herbig Ae star HD 142527 by near-infrared (H and K bands) adaptive optics imaging observations. The almost face-on disk consists of two bright arcs facing one another along the east-west direction (banana-split structure) and one spiral arm extending to the north from the western arc. The eastern arc is located at ~100-400 AU in radius from the star, and the western one is detected at ~150-490 AU. The stellar position is displaced from the center of the disk by about 20 AU to the north, and also from the center of the inner hole. The two arcs show an asymmetry in their size and brightness; the larger western arc is brighter than the east one by about 2 mag. The morphology of the disk, consisting of a banana-split structure and a spiral arm, most likely suggests the presence of an unseen eccentric binary and a recent stellar encounter.

Dynamics of cloud features on Uranus

Near-infrared adaptive optics imaging of Uranus by the Keck 2 telescope during 2003 and 2004 has revealed numerous discrete cloud features, 70 of which were used to extend the zonal wind profile of Uranus up to 60° N. We confirmed the presence of a north–south asymmetry in the circulation [Karkoschka, E., 1998. Science 280, 570–572], and improved its characterization. We found no clear indication of long term change in wind speed between 1986 and 2004, although results of Hammel et al. [Hammel, H.B., Rages, K., Lockwood, G.W., Karkoschka, E., de Pater, I., 2001. Icarus 153, 229–235] based on 2001 HST and Keck observations average ∼10 m/s less westward than earlier and later results, and 2003 observations by Hammel et al. [Hammel, H.B., de Pater, I., Gibbard, S., Lockwood, G.W., Rages, K., 2005. Icarus 175, 534–545] show increased wind speeds near 45° N, which we do not see in our 2003–2004 observations. We observed a wide range of lifetimes for discrete cloud features: some features evolve within ∼1 h, many have persisted at least one month, and one feature near 34° S (termed S34) seems to have persisted for nearly two decades, a conclusion derived with the help of Voyager 2 and HST observations. S34 oscillates in latitude between 32° S and 36.5° S, with a period of ∼1000 days, which may be a result of a non-barotropic Rossby wave. It also varied its longitudinal drift rate between −20°/day and −31°/day in approximate accord with the latitudinal gradient in the zonal wind profile, exhibiting behavior similar to that of the DS2 feature observed on Neptune [Sromovsky, L.A., Limaye, S.S., Fry, P.M., 1993. Icarus 105, 110–141]. S34 also exhibits a superimposed rapid oscillation with an amplitude of 0.57° in latitude and period of 0.7 days, which is approximately consistent with an inertial oscillation.

Near-infrared adaptive optics imaging of the satellites and individual rings of Uranus

We present the first Earth-based images of several of the individual faint rings of Uranus, as observed with the adaptive optics system on the W.M. Keck II telescope on four consecutive days in October 2003. We derive reflectivities based on multiple measurements of 8 minor moons of Uranus as well as Ariel and Miranda in filters centered at wavelengths of 1.25(J), 1.63(H), and 2.1(Kp) μm. These observations have a phase angle of 1.84°–1.96°. We find that the small satellites are somewhat less bright than in observations made by the HST at smaller phase angles, confirming an opposition surge effect. We calculate albedoes for the ring groups and for each ring separately. We find that the ε ring particles, as well as the particles in the three other ring groups, have albedoes near 0.043 at these phase angles. The equivalent depths of some of the individual rings are different than predicted based upon ring widths from occultation measurements (assuming a constant particle ring brightness); in particular the γ ring is fainter and the η ring brighter than expected. Our results indicate that q, the ratio of ε ring intensity at apoapse vs. periapse, is close to 3.2 ± 0.16 . This agrees well with a model that has a filling factor for the ε ring of 0.06 (Karkoschka, 2001, Icarus 151, 78–83). We also determine values of the north to south brightness ratio for the individual rings and find that in most cases they are close to unity.

Keck Adaptive Optics Imaging of 0.5 &lt; z &lt; 1 Field Galaxies from the Hubble Space Telescope Archive

We have employed natural guide star adaptive optics (AO) on the Keck II telescope to obtain near-infrared (H and K') images of three field galaxies, each of redshift greater than 0.5. These are among the highest-redshift non-active disk galaxies to be imaged with AO. Each of the galaxies was chosen because it had been observed previously with the Hubble Space Telescope (HST) Wide Field Planetary Camera 2 (WFPC2) by others. Our AO images in the near-infrared (NIR) closely match both the depth and high spatial resolution of those optical data. Combining the archival V and I data with our new H and K' images potentially produces a long-wavelength baseline at uniform resolution. The NIR data probe emission well longward of the 4000 Å break at these redshifts and provide stellar fluxes less contaminated by dust. We fitted two-dimensional galaxy bulge+disk models simultaneously in all bands and compare stellar population synthesis modeling to the photometry of these separated components. This is an initial foray into combining HST and AO imaging to produce a high spatial resolution multicolor data set for a large sample of faint galaxies. Our pilot program shows that NIR AO images from large ground-based observatories, augmented by HST images in the optical, can in principle provide a powerful tool for the analysis of faint field galaxies. However, the AO data signal-to-noise ratio will have to be increased, and AO PSFs need to be controlled more carefully than they were here.

Near-infrared adaptive optics imaging of nuclear spiral structure in the Seyfert galaxy NGC 3227

We present high spatial resolution, near-IR images in J, H, K of the nucleus of NGC3227, obtained with the Adaptive Optics bonnette on CFHT. The ~0.15 arcsec (17pc) resolution allows structures to be probed in the core region. Dust obscuration becomes significantly less pronounced at longer wavelengths, revealing the true geometry of the core region. We are able to identify two main features in our maps: (i) a spiraling association of knots with a counterpart in an HST F606W image; (ii) a smaller scale annulus, orthogonal to the spiral of knots. These features may provide a means to transport material inwards to fuel the active nucleus.

Near-Infrared Adaptive Optics Imaging of the Central Regions of Nearby S[CLC]c[/CLC] Galaxies. II. NGC 247 and NGC 2403

J, H, and K' images obtained with the Canada-France-Hawaii Telescope adaptive optics system are used to investigate the star-forming histories of the central regions of the Sc galaxies NGC 247 and NGC 2403. The brightest resolved red stars within 15'' of the nucleus of each galaxy are red supergiants (RSGs), indicating that the central few hundred parsecs of these galaxies experienced star formation within the last ~0.1 Gyr. While there are indications of galaxy-to-galaxy differences in the recent (t ≤ 0.1 Gyr) star-forming histories, a comparison of the K luminosity functions of stars near the centers of NGC 2403 and M33 indicates that, when averaged over gigayear timescales, the star-forming histories of the inner disks of these galaxies have been remarkably similar. This is consistent with suggestions that the long-term evolution of disks is defined by local characteristics such as mass density. It is demonstrated that NGC 247 and NGC 2403, like M33, harbor nuclear star clusters with stellar contents that differ from the surrounding central light concentrations, which in turn have near-infrared spectral energy distributions that are similar to old stellar systems. The nucleus of NGC 2403 is significantly bluer than that of the other two galaxies. If the nuclei of NGC 247, NGC 2403, and M33 are subject to similar amounts of extinction, then this indicates that NGC 2403 harbors the youngest nuclear star cluster in the sample. The K-band surface brightnesses near the centers of NGC 247 and NGC 2403 are 1–2 mag arcsec-2 lower than in M33. Finally, it is noted that young or intermediate-age nuclear star clusters are a common occurrence in nearby spirals, indicating that nuclear star formation in these objects is either continuous or episodic on timescales of 0.1–1 Gyr. This is consistent with models that have been proposed to explain the properties of the Galactic center.

Adaptive optics near-infrared imaging of NGC 2992 -- unveiling core structures related to radio figure-of-8 loops

We present near-infrared adaptive optics, Very Large Array (VLA) radio and Hubble Space Telescope (HST) optical imaging of the nearby Seyfert galaxy NGC 2992. Spiral structure and an extension to the west are traced down to the core region at the limiting resolution of our near-infrared images. A faint, diffuse loop of near-infrared and radio emission is also observed to the north, embedded within the prominent 2-arcsec radio loop previously observed to the north-west. Near-infrared colour maps and CO narrow-band imaging are then used to identify which regions may not be purely reddened stellar populations. Our new data provide evidence that the VLA radio-loop morphology in the shape of a figure of 8 represents two components superimposed: (1) outflow bubbles out of the plane of the disc, coincident with the extended emission-line region (EELR); (2) star formation along the spiral arm within the galaxy disc and through the dust lane. The near-infrared continuum emission associated with the outflowing radio bubbles suggests that the radio loops are driven by the active nucleus.

Near-Infrared Adaptive Optics Imaging of the Central Regions of Nearby S[CLC]c[/CLC] Galaxies. I. M33

Near-infrared images obtained with the Canada-France-Hawaii Telescope (CFHT) Adaptive Optics Bonnette (AOB) are used to investigate the stellar content within 18 arcsec of the center of the Local Group spiral galaxy M33. AGB stars with near-infrared spectral-energy distributions similar to those of giants in the solar neighborhood and Baade's Window are detected over most of the field. The bolometric luminosity function (LF) of these stars has a discontinuity near M_{bol} = -5.25, and comparisons with evolutionary tracks suggest that most of the AGB stars formed in a burst of star formation 1 - 3 Gyr in the past. The images are also used to investigate the integrated near-infrared photometric properties of the nucleus and the central light concentration. The nucleus is bluer than the central light concentration, in agreement with previous studies at visible wavelengths. The CO index of the central light concentration 0.5 arcsec from the galaxy center is 0.05, which corresponds to [Fe/H] = -1.2 for simple stellar systems. Hence, the central light concentration could not have formed from the chemically-enriched material that dominates the present-day inner disk of M33.

Stellar Content of the Galactic Starburst Template NGC 3603 from Adaptive Optics Observations

We present near-infrared adaptive optics imaging of the Galactic starburst template NGC 3603 and its stellar center HD 97950. There is clear evidence for the presence of stars down to 1 ${s}$ --> or less. No cutoff or turnover in the initial mass function is evident. Applying theoretical models of the pre-main-sequence evolution of intermediate-mass stars to the observed color-color diagram, the color-magnitude diagram, and the luminosity function, we constrain both the age distribution and the initial mass function. Within the systematic errors, this initial mass function follows a Salpeter power law with index ? ? -0.73 down to the observational limit of less than 1 ${s}$ -->. The stars with less than 4 ${s}$ --> appear to be younger than 106 yr, in contrast to previous age determinations of the high-mass content of HD 97950.

3.11. Resolved structure in the nuclear region of the ultraluminous infrared galaxy Mrk 273

As an example of the power of near-infrared (NIR) Adaptive Optics imaging in the detailed study of central regions of galaxies, we present high-resolution K-band imaging of Mrk 273, in combination with interferometric radio continuum data.

The Nuclear Stellar Core, the Hot Dust Source, and the Location of the Nucleus of NGC 1068

We present new near-infrared speckle and adaptive optics imaging and integral field spectroscopy of the nuclear region of NGC 1068. Ninety-four percent of the K-band light in the central 1'' originates from a ≤30 milliarcsecond diameter source whose position we determine to coincide within ±015 with the apex of the cone structure seen in the optical narrow emission lines, as well as the location of the flat spectrum radio component S1 and the 12 μm emission peak. We interpret the compact source as hot dust near the sublimation temperature within ~1 pc of the true nucleus of the galaxy. The remaining 6% of the light in the central 1'' comes from a moderately extincted stellar core centered on the nuclear position and of intrinsic size ~50 pc. We show that this nuclear stellar core is probably 5-16 × 108 yr in age and contributes at least 7% of the total nuclear luminosity of ~1 × 1011 L☉.

The Nuclear Stellar Cluster in NGC 1068

We present new near-infrared integral field spectroscopy and adaptive optics imaging of the nucleus of NGC 1068. Using the stellar CO absorption features in the H and K bands, we have identified a moderately extincted stellar core centered on the nuclear position and of intrinsic size ~50 pc. We show that this nuclear stellar core is probably 5-16 × 108 years in age and contributes at least 7% of the total nuclear luminosity of ~1 × 1011 L⊙.

Adaptive Optics Near-Infrared Imaging of R136 in 30 Doradus: The Stellar Population of a Nearby Starburst

view Abstract Citations (176) References (56) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Adaptive Optics Near-Infrared Imaging of R136 in 30 Doradus: The Stellar Population of a Nearby Starburst Brandl, B. ; Sams, B. J. ; Bertoldi, F. ; Eckart, A. ; Genzel, R. ; Drapatz, S. ; Hofmann, R. ; Loewe, M. ; Quirrenbach, A. Abstract We report 0".15 resolution near-infrared (NIR) imaging of R136, the central region of 30 Doradus in the large Magellanic Cloud. Our 12".8 x 12".8 images were recorded with the MPE camera SHARP II at the 3.6 m ESO telescope, using the adaptive optics system COME ON+. The high spatial resolution and sensitivity (20th magnitude in K) of our observations allow our H- and K-band images to be compared and combined with recent Hubble Space Telescope (HST) WFPC2 data of R136. We fit theoretical models with variable foreground extinction to the observed magnitudes of ∼1000 stars (roughly half of which were detected in HST and NIR bands) and derive the stellar population in this starburst region. We find no red giants or supergiants; however, we detect ∼110 extremely red sources which are probably young, pre-main-sequence low- or intermediate-mass stars. We obtained narrow-band images to identify known and new Wolf-Rayet stars by their He 11(2.189 μm) and Bry (2.166 μm) emission lines. The presence of W-R stars and absence of red supergiants narrow the cluster age to ∼3-5 Myr, while the derived ratio of W-R to 0 stars of 0.05 in the central region favors an age of 3.5 Myr, with a relatively short starburst duration. For the 0 stars, the core radius is found to be 0.1 pc and appears to decrease with increasing stellar mass. The slope of the mass function function is Γ = -1.6 on average, but it steepens with increasing distance from the cluster center from Γ = -1.3 in the inner 0.4 pc to Γ = -2.2 outside 0.8 pc for stars more massive than 12 Msun. The radial variation of the mass function reveals strong mass segregation that is probably due to the cluster's dynamical evolution. Publication: The Astrophysical Journal Pub Date: July 1996 DOI: 10.1086/177507 Bibcode: 1996ApJ...466..254B Keywords: ISM: H II REGIONS; INFRARED: STARS; ISM: INDIVIDUAL NAME: 30 DORADUS; GALAXIES: MAGELLANIC CLOUDS; STARS: EARLY-TYPE; TECHNIQUES: IMAGE PROCESSING full text sources ADS | data products SIMBAD (161) MAST (1) ESA (1) CDS (1)