Peter J. McGregor

Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts, United States

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Publications (73)231.97 Total impact

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    ABSTRACT: We map the kinematics of the inner (200 pc) narrow-line region (NLR) of the Seyfert 2 galaxy NGC 1068 using the instrument Near-infrared Integral Field Spectrograph and adaptive optics at the Gemini North telescope. Channel maps and position-velocity diagrams are presented at a spatial resolution of ≅8 pc and spectral resolution ̃5300 in the emission lines [Fe II] λ1.644 μm, H2 λ2.122 μm and Brγ. The [Fe II] emission line provides a better coverage of the NLR outflow than the previously used [O III] λ5007 emission line, extending beyond the area of the bipolar cone observed in Brγ and [O III]. This is mainly due to the contribution of the redshifted channels to the north-east of the nucleus, supporting its origin in a partial ionized zone with additional contribution from shocks of the outflowing gas with the galactic disc. We modelled the kinematics and geometry of the [Fe II] emitting gas finding good agreement with the data for outflow models with conical and lemniscate (or hourglass) geometry. We calculate a mass outflow rate of 1.9^{+2}_{-1} M☉ yr-1 but a power for the outflow of only 0.08 per cent LBol. The molecular (H2) gas kinematics is completely distinct from that of [Fe II] and Brγ, showing radial expansion in an off-centred ̃100 pc radius ring in the galaxy plane. The expansion velocity decelerates from ≈200 km s-1 in the inner border of the ring to approximately zero at the outer border where our previous studies found a 10 Myr stellar population.
    Monthly Notices of the Royal Astronomical Society 11/2014; 445(3). DOI:10.1093/mnras/stu1637 · 5.23 Impact Factor
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    ABSTRACT: We map the kinematics of the inner (200 pc) narrow-line region (NLR) of the Seyfert 2 galaxy NGC 1068 using the instrument NIFS and adaptative optics at the Gemini North Telescope. Channel maps and position-velocity diagrams are presented at a spatial resolution of $\sim$ 10 pc and spectral resolution $\sim$ 5300 in the emission lines [Fe II] {\lambda} 1.644 {\mu}m, H$_2$ {\lambda} 2.122 {\mu}m and Br{\gamma}. The [Fe II] emission line provides a better coverage of the NLR outflow than the previously used [O III] {\lambda} 5007 emission line, extending beyond the area of the bi-polar cone observed in Br{\gamma} and [O III]. This is mainly due to the contribution of the redshifted channels to the NE of the nucleus, supporting its origin in a partial ionized zone with additional contribution from shocks of the outflowing gas with the galactic disc. We modeled the kinematics and geometry of the [Fe II] emitting gas finding good agreement with the data for outflow models with conical and lemniscate (or hourglass) geometry. We calculate a mass outflow rate $1.9^{+1.9}_{-0.7}$ M$_{\odot}~$yr$^{-1}$ but a power for the outflow of only 0.08% L$_{Bol}$. The molecular (H$_2$) gas kinematics is completely distinct from that of [Fe II] and Br{\gamma}, showing radial expansion in an off-centered $\sim$ 100 pc radius ring in the galaxy plane. The expansion velocity decelerates from $\sim$ 200 km/s in the inner border of the ring to approximately zero at the outer border where our previous studies found a 10 Myr stellar population.
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    ABSTRACT: To achieve the high adaptive optics sky coverage necessary to allow the GMT Integral-Field Spectrograph to access key scientific targets, the on-instrument adaptive-optics wavefront-sensing system must patrol the full 180 arcsecond diameter guide field passed to the instrument. Starlight must be held stationary on the wavefront sensor (accounting for flexure, differential refraction and non-sidereal tracking rates) to ~ 1 milliarcsecond to provide the stable position reference signal for deep AO observations and avoid introducing image blur. Hence a tight tolerance of 1/180,000 is placed on the positioning and encoding accuracy for the cryogenic On-Instrument Wave-Front Sensor feed. GMTIFS will achieve this requirement using a beam-steering mirror system as an optical relay for starlight from across the accessible guide field. The system avoids hysteresis and backlash by eliminating friction and avoiding gearing while maintaining high setting speed and accuracy with a precision feedback loop. Here we present the design of the relay system and the technical solution deployed to meet the challenging specifications for drive rate, accuracy and positional encoding of the beam-steering system.
    SPIE Astronomical Telescopes + Instrumentation; 07/2014
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    ABSTRACT: The Gemini High-Resolution Optical SpecTrograph (GHOST) is the newest instrument being developed for the Gemini telescopes, in a collaboration between the Australian Astronomical Observatory (AAO), the NRC - Herzberg in Canada and the Australian National University (ANU). We describe the process of design optimisation that utilizes the unique strengths of the new partner, NRC - Herzberg, the design and need for the slit viewing camera system, and we describe a simplification for the lenslet-based slit reformatting. Finally, we out- line the updated project plan, and describe the unique scientific role this instrument will have in an international context, from exoplanets through to the distant Universe.
    SPIE Astronomical Telescopes + Instrumentation; 07/2014
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    ABSTRACT: We study the spatially resolved stellar kinematics of two star-forming galaxies at z similar to 0.1 from the larger DYnamics of Newly Assembled Massive Objects (DYNAMO) sample. These galaxies, which have been characterized by high levels of star formation and large ionized-gas velocity dispersions, are considered possible analogues to high-redshift clumpy discs. They were observed using the Gemini Multi-Object Spectrograph instrument in integral field spectroscopy (IFS) mode at the Gemini Observatory with high spectral resolution (R similar or equal to 5400, equivalent to sigma similar or equal to 24 km s(-1) at the observed wavelengths) and similar to 6 h exposure times in order to measure the resolved stellar kinematics via absorption lines. We also obtain higher quality emission-line kinematics than previous observations. The spatial resolution (1.2 kpc) is sufficient to show that the ionized gas in these galaxies (as traced by H beta emission) is morphologically irregular, forming multiple giant clumps while stellar continuum light is smooth and well described by an exponential profile. Clumpy gas morphologies observed in IFS data are confirmed by complementary narrow-band H alpha imaging from the Hubble Space Telescope. Morphological differences between the stars and ionized gas are not reflected dynamically as stellar kinematics are found to be closely coupled to the kinematics of the ionized gas: both components are smoothly rotating with large velocity dispersions (similar to 40 km s(-1)) suggesting that the high gas dispersions are not primarily driven by star formation feedback. In addition, the stellar population ages of these galaxies are estimated to be quite young (60-500 Myr). The large velocity dispersions measured for these young stars suggest that we are seeing the formation of thick discs and/or stellar bulges in support of recent models which produce these from clumpy galaxies at high redshift.
    Monthly Notices of the Royal Astronomical Society 06/2014; 442(4):3206-3221. DOI:10.1093/mnras/stu1029 · 5.23 Impact Factor
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    ABSTRACT: We present a revised measurement of the mass of the central black hole (Mbh) in the Seyfert 1 galaxy NGC 4151. The new stellar dynamical mass measurement is derived by applying an axisymmetric orbit-superposition code to near-infrared integral field data obtained using adaptive optics with the Gemini NIFS spectrograph. When our models attempt to fit both the NIFS kinematics and additional low spatial resolution kinematics, our results depend sensitively on how chi-squared is computed--probably a consequence of complex bar kinematics that manifest immediately outside the nuclear region. The most robust results are obtained when only the high spatial resolution kinematic constraints in the nuclear region are included in the fit. Our best estimates for the BH mass and H-band mass-to-light ratio are Mbh~(3.76+/-1.15)E7 Msun (1-sigma error) and M/L(H-band)~0.34+/-0.03 Msun/Lsun (3-sigma error), respectively (the quoted errors reflect the model uncertainties). Our BH mass measurement is consistent with estimates from both reverberation mapping (3.57[+0.45/-0.37]E7 Msun) and gas kinematics (3.0[+0.75/-2.2]E7 Msun; 1-sigma errors), and our best-fit mass-to-light ratio is consistent with the photometric estimate of M/L(H-band)=0.4+/-0.2 Msun/Lsun. The NIFS kinematics give a central bulge velocity dispersion sigma_c=116+/-3 km/s, bringing this object slightly closer to the M-sigma relation for quiescent galaxies. Although NGC 4151 is one of only a few Seyfert 1 galaxies in which it is possible to obtain a direct dynamical BH mass measurement--and thus, an independent calibration of the reverberation mapping mass scale--the complex bar kinematics makes it less than ideally suited for this purpose.
    The Astrophysical Journal 06/2014; 791(1). DOI:10.1088/0004-637X/791/1/37 · 6.28 Impact Factor
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    ABSTRACT: In this letter we report the discovery of CO fluxes, suggesting very high gas fractions in three disk galaxies seen in the nearby Universe (z ~ 0.1). These galaxies were investigated as part of the DYnamics of Newly Assembled Massive Objects (DYNAMO) survey. High-resolution Hubble Space Telescope imaging of these objects reveals the presence of large star forming clumps in the bodies of the galaxies, while spatially resolved spectroscopy of redshifted Halpha reveals the presence of high dispersion rotating disks. The internal dynamical state of these galaxies resembles that of disk systems seen at much higher redshifts (1 < z < 3). Using CO(1-0) observations made with the Plateau de Bure Interferometer, we find gas fractions of 20-30% and depletion times of tdep ~ 0.5 Gyr (assuming a Milky Way-like CO conversion factor). These properties are unlike those expected for low- redshift galaxies of comparable specific star formation rate, but they are normal for their high-z counterparts. DYNAMO galaxies break the degeneracy between gas fraction and redshift, and we show that the depletion time per specific star formation rate for galaxies is closely tied to gas fraction, independent of redshift. We also show that the gas dynamics of two of our local targets corresponds to those expected from unstable disks, again resembling the dynamics of high-z disks. These results provide evidence that DYNAMO galaxies are local analogues to the clumpy, turbulent disks, which are often found at high redshift.
    The Astrophysical Journal Letters 05/2014; 790(2). DOI:10.1088/2041-8205/790/2/L30 · 5.60 Impact Factor
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    ABSTRACT: We study the spatially resolved stellar kinematics of two star-forming galaxies at z = 0.1 from the larger DYnamics of Newly Assembled Massive Objects (DYNAMO) sample. These galaxies, which have been characterized by high levels of star formation and large ionized gas velocity dispersions, are considered possible analogs to high-redshift clumpy disks. They were observed using the GMOS instrument in integral field spectroscopy (IFS) mode at the Gemini Observatory with high spectral resolution (R=5400, equivalent to 24 km/s at the observed wavelengths) and 6 hour exposure times in order to measure the resolved stellar kinematics via absorption lines. We also obtain higher-quality emission line kinematics than previous observations. The spatial resolution (1.2 kpc) is sufficient to show that the ionized gas in these galaxies (as traced by H-beta emission) is morphologically irregular, forming multiple giant clumps while stellar continuum light is smooth and well described by an exponential profile. Clumpy gas morphologies observed in IFS data are confirmed by complementary narrow band H-alpha imaging from the Hubble Space Telescope. Morphological differences between the stars and ionized gas are not reflected dynamically as stellar kinematics are found the be closely coupled to the kinematics of the ionized gas: both components are smoothly rotating with large velocity dispersions (~40 km/s) suggesting that the high gas dispersions are not primarily driven by star-formation feedback. In addition, the stellar population ages of these galaxies are estimated to be quite young (60-500 Myr). The large velocity dispersions measured for these young stars suggest that we are seeing the formation of thick disks and/or stellar bulges in support of recent models which produce these from clumpy galaxies at high redshift.
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    ABSTRACT: We present emission-line flux distributions and ratios for the inner 200pc of the narrow-line region of the Seyfert2 galaxy NGC1068, using observations obtained with the Gemini Near-infrared Integral Field Spectrograph (NIFS) in the J, H and K bands at a spatial resolution of 10pc and spectral resolution of 5300. The molecular gas emission - traced by the K-band H_2 emission lines - outlines an off-centered circumnuclear ring with a radius of 100pc showing thermal excitation. The ionized gas emission lines show flux distributions mostly outlining the previously known [OIII]5007 ionization bicone. But while the flux distributions in the HI and HeII emission lines are very similar to that observed in [OIII], the flux distribution in the [FeII] emission lines is more extended and broader than a cone close to the nucleus, showing a "double bowl" or `hourglass" structure". This difference is attributed to the fact that the [FeII] emission, besides coming from the fully ionized region, comes also from the more extended partially ionized regions, in gas excited mainly by X-rays from the active galactic nucleus. A contribution to the [FeII] emission from shocks along the bicone axis to NE and SW of the nucleus is also supported by the enhancement of the [FeII](1.2570)/[PII](1.1885) and [FeII](1.2570)/Pabeta emission-line ratios at these locations and is attributed to the interaction of the radio jet with the NLR. The mass of ionized gas in the inner 200pc of NGC1068 is MHII~2.2E4 M_Sun, while the mass of the H2 emitting gas is only M_{H2}~29M_Sun. Taking into account the dominant contribution of the cold molecular gas, we obtain an estimate of the total molecular gas mass of Mcold~2E7 M_Sun.
    Monthly Notices of the Royal Astronomical Society 04/2014; 442(1). DOI:10.1093/mnras/stu843 · 5.23 Impact Factor
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    ABSTRACT: The origin of bipolar outflow asymmetry in young stellar objects (YSOs) remains poorly understood. It may be due to an intrinsically asymmetric outflow launch mechanism, or it may be caused by the effects of the ambient medium surrounding the YSO. Answering this question is an important step in understanding outflow launching. We have investigated the bipolar outflows driven by the T Tauri star DG Tauri on scales of hundreds of AU, using the Near-infrared Integral Field Spectrograph (NIFS) on Gemini North. The approaching outflow consists of a well-collimated jet, nested within a lower-velocity disc wind. The receding outflow is composed of a single-component bubble-like structure. We analyse the kinemat- ics of the receding outflow using kinetic models, and determine that it is a quasi-stationary bubble with an expanding internal velocity field. We propose that this bubble forms because the receding counterjet from DG Tau is obstructed by a clumpy ambient medium above the circumstellar disc surface, based on similarities between this structure and those found in the modeling of active galactic nuclei outflows. We find evidence of interaction between the obscured counterjet and clumpy ambient material, which we attribute to the large molecular envelope around the DG Tau system. An analytical model of a momentum-driven bubble is shown to be consistent with our interpretation. We conclude that the bipolar outflow from DG Tau is intrinsically symmetric, and the observed asymmetries are due to environmental effects. This mechanism can potentially be used to explain the observed bipolar asymmetries in other YSO outflows.
    Monthly Notices of the Royal Astronomical Society 04/2014; 442(1). DOI:10.1093/mnras/stu788 · 5.23 Impact Factor
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    ABSTRACT: Investigating the outflows emanating from young stellar objects (YSOs) on sub-arcsecond scales provides important clues to the nature of the underlying accretion-ejection process occurring near the central protostar. We have investigated the structures and kinematics of the outflows driven by the YSO DG Tauri, using the Near-infrared Integral Field Spectrograph (NIFS) on Gemini North. The blueshifted outflow shows two distinct components in [Fe II] 1.644 micron emission, which are separated using multi-component line fitting. A stationary recollimation shock is observed, in agreement with previous X-ray and FUV observations. The presence of this shock indicates that the innermost streamlines of the high-velocity component are launched at a very small radius, 0.01-0.15 AU, from the central star. The jet accelerates and expands downstream of the recollimation shock; the 'acceleration' is likely a sign of velocity variations in the jet. No evidence of rotation is found, and we compare this non-detection to previous counter-claims. Moving jet knots, likely the result of the jet velocity variations, are observed. One of these knots moves more slowly than previously observed knots, and the knot ejection interval appears to be non-periodic. An intermediate-velocity component surrounds this central jet, and is interpreted as the result of a turbulent mixing layer along the jet boundaries. Such lateral entrainment requires the presence of a magnetic field of strength a few mG or less at hundreds of AU above the disc surface, which is argued to be a reasonable proposition. In H2 1-0 S(1) 2.1218 micron emission, a wide-angle, intermediate-velocity blueshifted outflow is observed. Both outflows are consistent with being launched by a magnetocentrifugal disc wind, although an X-wind origin for the high-velocity jet cannot be ruled out.
    Monthly Notices of the Royal Astronomical Society 04/2014; 441(2). DOI:10.1093/mnras/stu654 · 5.23 Impact Factor
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    ABSTRACT: The origin of bipolar outflow asymmetry in young stellar objects (YSOs) remains poorly understood. It may be due to an intrinsically asymmetric outflow launch mechanism, or it may be caused by the effects of the ambient medium surrounding the YSO. Answering this question is an important step in understanding outflow launching. We have investigated the bipolar outflows driven by the T Tauri star DG Tauri on scales of hundreds of AU, using the Near-infrared Integral Field Spectrograph (NIFS) on Gemini North. The approaching outflow consists of a well-collimated jet, nested within a lower-velocity disc wind. The receding outflow is composed of a single-component bubble-like structure. We analyse the kinemat- ics of the receding outflow using kinetic models, and determine that it is a quasi-stationary bubble with an expanding internal velocity field. We propose that this bubble forms because the receding counterjet from DG Tau is obstructed by a clumpy ambient medium above the circumstellar disc surface, based on similarities between this structure and those found in the modeling of active galactic nuclei outflows. We find evidence of interaction between the obscured counterjet and clumpy ambient material, which we attribute to the large molecular envelope around the DG Tau system. An analytical model of a momentum-driven bubble is shown to be consistent with our interpretation. We conclude that the bipolar outflow from DG Tau is intrinsically symmetric, and the observed asymmetries are due to environmental effects. This mechanism can potentially be used to explain the observed bipolar asymmetries in other YSO outflows.
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    ABSTRACT: The Gemini Multi-conjugate Adaptive Optics System - GeMS, a facility instrument mounted on the Gemini South telescope, delivers a uniform, near diffraction limited images at near infrared wavelengths (0.95 microns- 2.5 microns) over a field of view of 120 arc seconds. GeMS is the first sodium layer based multi laser guide star adaptive optics system used in astronomy. It uses five laser guide stars distributed on a 60 arc seconds square constellation to measure for atmospheric distortions and two deformable mirrors to compensate for it. In this paper, the second devoted to describe the GeMS project, we present the commissioning, overall performance and operational scheme of GeMS. Performance of each sub-system is derived from the commissioning results. The typical image quality, expressed in full with half maximum, Strehl ratios and variations over the field delivered by the system are then described. A discussion of the main contributor to performance limitation is carried-out. Finally, overheads and future system upgrades are described.
    Monthly Notices of the Royal Astronomical Society 02/2014; 440(2). DOI:10.1093/mnras/stu403 · 5.23 Impact Factor
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    ABSTRACT: (abridged) DYNAMO is a multi-wavelength, spatially-resolved survey of local ($z \sim 0.1$) star-forming galaxies designed to study evolution through comparison with samples at z~2. Half of the sample has integrated H-alpha luminosities of >$10^{42}$ erg/s, the typical lower limit for resolved spectroscopy at z~2. The sample covers a range in stellar mass ($10^9$-$10^{11}$ Msun) and star-formation rate (0.2-100 Msun/yr). In this first paper of a series, we present integral-field spectroscopy of H-alpha emission for the sample of 67 galaxies. We infer gas fractions in our sample as high as ~0.8, higher than typical for local galaxies. Gas fraction correlates with stellar mass in galaxies with star-formation rates below 10 Msun/yr, as found by COLDGASS, but galaxies with higher star-formation rates have higher than expected gas fractions. There is only a weak correlation, if any, between gas fraction and gas velocity dispersion. Galaxies in the sample visually classified as disc-like are offset from the local stellar-mass Tully-Fisher relation to higher circular velocities, but this offset vanishes when both gas and stars are included in the baryonic Tully-Fisher relation. The mean gas velocity dispersion of the sample is ~50 km/s, and V/sigma ranges from 2 to 10 for most of the discs, similar to 'turbulent' galaxies at high redshift. Half of our sample show disc-like rotation, while ~20 percent show no signs of rotation. The division between rotating and non-rotating is approximately...
    Monthly Notices of the Royal Astronomical Society 10/2013; 437(2). DOI:10.1093/mnras/stt1882 · 5.23 Impact Factor
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    ABSTRACT: The outflows driven by young stellar objects provide important clues to the nature of the underlying accretion-ejection mechanism, as well as probing the physical conditions around the object. We present sub-arcsecond-resolution spectroimaging data of the outflows of the young stellar object DG Tauri, obtained from 2005-2013 in four distinct epochs using the Near-infrared Integral Field Spectrograph (NIFS) on Gemini North. These data allow us to simultaneously probe the kinematics and structure of the outflows. We rigorously separate the two [Fe II] 1.644 μm emission-line components in the approaching outflow for the first time. The high-velocity approaching jet is dominated by moving shock-excited 'knots', which emerge with a period of ~5 years and may be linked to observed bursts of accretion activity (see poster by Chou et al). The presence of a stationary recollimation shock implies a jet terminal velocity of 400-700 km s-1 and a jet launch radius of 0.02-0.07 AU. Jet acceleration is observed well beyond the height where magnetocentrifugal acceleration should cease. This is successfully modeled as a form of magnetic acceleration internal to the jet. No jet rotation is observed. The low-velocity approaching component is successfully modeled as a turbulent entrainment layer along the jet boundary, which requires the presence of a ~20-60 mG magnetic field around the jet. The receding outflow takes the form of a large bubble. We determine that this is due to the receding counter-jet being blocked by ambient material. Further analysis of our multi-epoch data set will allow us to track the evolution of the outflows over multiple accretion-ejection events.
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    ABSTRACT: We present optical spectroscopic/spectrophotometric monitoring of four active T Tauri stars (DG Tau, RY Tau, XZ Tau, RW Aur A) at high spectral resolution (R > 10^4) and wide spectral coverage (?10500Å) using CFHT-ESPaDOnS. The goal of the study is to investigate the correlation between time variable mass ejection seen in the jet/wind structure of the driving source and time variable mass accretion probed by optical emission lines. Through the observations for 10-20 years, this may allow us to constrain the understanding of the jet/wind launching mechanism, the location of the launching region, and the physical link with magnetospheric mass accretion. Our initial results in 2010-2012 have confirmed the presence of long-term time variability separates from the daily and monthly variability. This is so far consistent with the idea that these line profiles have a long-term variability (3-20 year) related to episodic mass ejection suggested by the structures in the extended flow components. We also investigate the correlations between equivalent widths and between luminosities for different lines. We find that these correlations are consistent with the present paradigm of steady magnetospheric mass accretion and emission line regions that are close to the star. Monitoring observations of extended flow components are also in progress using Gemini-NIFS.
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    ABSTRACT: The Gemini South Adaptive Optics Imager (GSAOI) is the imaging camera to be used with the Multi-Conjugate Adaptive Optics system (GeMS) at Gemini South. GeMS and GSAOI are capable of delivering a diffraction limited images in the Near-Ifrared (0.9-2.5 micrometers) over an 85" square field of view. The focal plane of the instrument is covered by 2 x 2 array of HAWAII 2RG detectors and has a plate scale of 0.02". The instrument optics are all-refractive and coupled with the superb spatial resolution take a full advantage of the unprecedented image quality delivered by GeMS. GSAOI went through several commissioning runs during the southern summer of 2011/2012. In this presentation a brief summary of the system is provided, along with relevant commissioning information and some preliminary science results.
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    ABSTRACT: We present adaptive optics-assisted J- and K-band integral field spectroscopy of the inner 300 x 300 pc of the Seyfert 2 galaxy NGC1068. The data were obtained with the Gemini NIFS integral field unit spectrometer, which provided us with high-spatial and -spectral resolution sampling. The wavelength range covered by the observations allowed us to study the [CaVIII], [SiVI], [SiVII], [AlIX] and [SIX] coronal-line (CL) emission, covering ionization potentials up to 328 eV. The observations reveal very rich and complex structures, both in terms of velocity fields and emission-line ratios. The CL emission is elongated along the NE-SW direction, with the stronger emission preferentially localized to the NE of the nucleus. CLs are emitted by gas covering a wide range of velocities, with maximum blueshifts/redshifts of ~ -1600/1000 km/s. There is a trend for the gas located on the NE side of the nucleus to be blueshifted while the gas located towards the SW is redshifted. The morphology and the kinematics of the near-infrared CLs are in very good agreement with the ones displayed by low-ionization lines and optical CLs, suggesting a common origin. The line flux distributions, velocity maps, ionization structure (traced by the [SiVII]/[SiVI] emission-line ratio) and low ionization emission-line ratios (i.e., [FeII]/Pa\beta\ and [FeII]/[PII]) suggest that the radio jet plays an important role in the structure of the coronal line region of this object, and possibly in its kinematics.
    Monthly Notices of the Royal Astronomical Society 12/2012; 430(3). DOI:10.1093/mnras/stt064 · 5.23 Impact Factor
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    ABSTRACT: We report the results of high spatial and spectral resolution integral-field spectroscopy of the central ~3 x 3 arcsec^2 of the active galaxy NGC 1275 (Perseus A), based on observations with the Near-infrared Integral Field Spectrograph (NIFS) and the ALTAIR adaptive-optics system on the Gemini North telescope. The circum-nuclear disc in the inner R~50 pc of NGC 1275 is seen in both the H2 and [FeII] lines. The disc is interpreted as the outer part of a collisionally-excited turbulent accretion disc. The kinematic major axis of the disc at a position angle of 68 deg is oriented perpendicular to the radio jet. A streamer-like feature to the south-west of the disc, detected in H2 but not in [FeII], is discussed as one of possibly several molecular streamers, presumably falling into the nuclear region. Indications of an ionization structure within the disc are deduced from the HeI and Br gamma emission lines, which may partially originate from the inner portions of the accretion disc. The kinematics of these two lines agrees with the signature of the circum-nuclear disc, but both lines display a larger central velocity dispersion than the H2 line. The rovibrational H2 transitions from the core of NGC 1275 are indicative of thermal excitation caused by shocks and agree with excitation temperatures of ~1360 and ~4290 K for the lower- and higher-energy H2 transitions, respectively. The data suggest X-ray heating as the dominant excitation mechanism of [FeII] emission in the core, while fast shocks are a possible alternative. The [FeII] lines indicate an electron density of ~4000 cm^{-3}. The H2 disc is modelled using simulated NIFS data cubes of H2 emission from inclined discs in Keplerian rotation around a central mass. Assuming a disc inclination of 45 deg +/- 10 deg, the best-fitting models imply a central mass of (8^{+7}_{-2}) x 10^8 Msun. (abridged)
    Monthly Notices of the Royal Astronomical Society 11/2012; 429(3). DOI:10.1093/mnras/sts502 · 5.23 Impact Factor
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    ABSTRACT: The Gemini South Adaptive-Optics Imager (GSAOI) has recently been commissioned on the Gemini South telescope. Designed for use with the Gemini GeMS Multi-Conjugate Adaptive Optics System, GSAOI makes use of the HAWAII- 2RG (H2RG) On-Detector Guide Window (ODGW) feature where guide windows positioned in each of the four H2RG detectors provide GeMS with tip-tilt and flexure corrections. This paper concentrates on the complex software and firmware required for operating the ODGWs and for delivering the performance required by GeMS. Software architecture, algorithms, performance and the implementation platform for the current on-telescope solution are detailed.
    Proceedings of SPIE - The International Society for Optical Engineering 09/2012; DOI:10.1117/12.925273 · 0.20 Impact Factor

Publication Stats

647 Citations
231.97 Total Impact Points

Institutions

  • 2014
    • Harvard-Smithsonian Center for Astrophysics
      Cambridge, Massachusetts, United States
  • 2000–2014
    • Australian National University
      • • Research School of Astronomy & Astrophysics
      • • Mount Stromlo Observatory
      Canberra, Australian Capital Territory, Australia
  • 2012
    • Universidade Federal Fluminense
      Vila Real da Praia Grande, Rio de Janeiro, Brazil
  • 2008–2010
    • Space Telescope Science Institute
      Baltimore, Maryland, United States