ORCID Profile
0000-0003-0303-3855
Current Organisation
University of Tasmania
Does something not look right? The information on this page has been harvested from data sources that may not be up to date. We continue to work with information providers to improve coverage and quality. To report an issue, use the Feedback Form.
In Research Link Australia (RLA), "Research Topics" refer to ANZSRC FOR and SEO codes. These topics are either sourced from ANZSRC FOR and SEO codes listed in researchers' related grants or generated by a large language model (LLM) based on their publications.
Stellar Astronomy and Planetary Systems | Astronomical and Space Sciences | Galactic Astronomy | Astronomical and Space Instrumentation
Expanding Knowledge in the Physical Sciences | Climate Variability (excl. Social Impacts) |
Publisher: Oxford University Press (OUP)
Date: 09-12-2016
Publisher: Cambridge University Press (CUP)
Date: 12-2006
Publisher: American Astronomical Society
Date: 11-11-2013
Publisher: American Astronomical Society
Date: 15-07-2021
Abstract: We present Keck/NIRC2 adaptive optics imaging of planetary microlensing event MOA-2007-BLG-400 that resolves the lens star system from the source. We find that the MOA-2007-BLG-400L planetary system consists of a 1.71 ± 0.27 M Jup planet orbiting a 0.69 ± 0.04 M ⊙ K-dwarf host star at a distance of 6.89 ± 0.77 kpc from the Sun. So, this planetary system probably resides in the Galactic bulge. The planet–host star projected separation is only weakly constrained due to the close-wide light-curve degeneracy the 2 σ projected separation ranges are 0.6–1.0 au and 4.7–7.7 au for close and wide solutions, respectively. This host mass is at the top end of the range of masses predicted by a standard Bayesian analysis. Our Keck follow-up program has now measured lens-source separations for six planetary microlensing events, and five of these six events have host star masses above the median prediction under the assumption that assumes that all stars have an equal chance of hosting planets detectable by microlensing. This suggests that more massive stars may be more likely to host planets of a fixed mass ratio that orbit near or beyond the snow line. These results also indicate the importance of host star mass measurements for exoplanets found by microlensing. The microlensing survey imaging data from NASA’s Nancy Grace Roman Space Telescope (formerly WFIRST) mission will be doing mass measurements like this for a huge number of planetary events.
Publisher: American Astronomical Society
Date: 21-05-2021
Abstract: The microlensing event OGLE-2017-BLG-1434 features a cold super-Earth planet that is 1 of 11 microlensing planets with a planet–host-star mass ratio of q 1 × 10 −4 . We provide an additional mass–distance constraint on the lens host using near-infrared adaptive optics photometry from Keck/NIRC2. We are able to determine a flux excess of K L = 16.96 ± 0.11, which most likely comes entirely from the lens star. Combining this with constraints from the large Einstein ring radius, θ E = 1.40 ± 0.09 mas, and OGLE parallax we confirm this event as a super-Earth with a mass of m p = 4.43 ± 0.25 M ⊕ . This system lies at a distance of D L = 0.86 ± 0.05 kpc from Earth and the lens star has a mass of M L = 0.234 ± 0.012 M ⊙ . We confirm that with a star–planet mass ratio of q = 0.57 × 10 −4 , OGLE-2017-BLG-1434 lies near the inflexion point of the planet–host mass-ratio power law.
Publisher: American Astronomical Society
Date: 10-06-2014
Publisher: Oxford University Press (OUP)
Date: 25-05-2017
Abstract: We report that the serendipitous young Large Magellanic Cloud cluster NGC 1971 exhibits an extended main-sequence turn-off (eMSTO) possibly originated mostly by a real age spread. We used CT1 Washington photometry to produce a colour–magnitude diagram (CMD) with the fiducial cluster features. From its eMSTO, we estimated an age spread of ∼170 Myr (observed age range 100–280 Myr), once observational errors, stellar binarity, overall metallicity variations and stellar rotation effects were subtracted in quadrature from the observed age width.
Publisher: EDP Sciences
Date: 05-2012
Publisher: Oxford University Press (OUP)
Date: 11-2001
Publisher: American Astronomical Society
Date: 16-08-2011
Publisher: American Astronomical Society
Date: 02-02-2010
Publisher: American Astronomical Society
Date: 07-10-2010
Publisher: American Astronomical Society
Date: 10-2022
Abstract: We measure homogeneous distances to M31 and 38 associated stellar systems (−16.8 ≤ M V ≤ −6.0), using time-series observations of RR Lyrae stars taken as part of the Hubble Space Telescope Treasury Survey of M31 Satellites. From orbits of new/archival Advanced Camera for Surveys imaging, we identify RR Lyrae stars and determine their periods and mean magnitudes to a typical precision of 0.01 day and 0.04 mag. Based on period–Wesenheit–metallicity relationships consistent with the Gaia eDR3 distance scale, we uniformly measure heliocentric and M31-centric distances to a typical precision of ∼20 kpc (3%) and ∼10 kpc (8%), respectively. We revise the 3D structure of the M31 galactic ecosystem and: (i) confirm a highly anisotropic spatial distribution such that ∼80% of M31's satellites reside on the near side of M31 this feature is not easily explained by observational effects (ii) affirm the thin (rms 7–23 kpc) planar “arc” of satellites that comprises roughly half (15) of the galaxies within 300 kpc from M31 (iii) reassess the physical proximity of notable associations such as the NGC 147/185 pair and M33/AND xxii and (iv) illustrate challenges in tip-of-the-red-giant branch distances for galaxies with M V − 9.5, which can be biased by up to 35%. We emphasize the importance of RR Lyrae for accurate distances to faint galaxies that should be discovered by upcoming facilities (e.g., Rubin Observatory). We provide updated luminosities and sizes for our s le. Our distances will serve as the basis for future investigation of the star formation and orbital histories of the entire known M31 satellite system.
Publisher: Cambridge University Press (CUP)
Date: 08-2006
DOI: 10.1017/S1743921307007181
Abstract: The United Nations Office for Outer Space Affairs and the International Heliophysical Year (IHY) community have joined hands to deploy arrays of small, inexpensive instruments such as magnetometers, radio telescopes, GPS receivers, all-sky cameras, and particle detectors around the world to provide global measurements of ionospheric, magnetospheric and heliospheric phenomena. The small instrument programme is envisioned as a partnership between instrument providers, and instrument hosts in developing countries as one of United Nations Basic Space Science (UNBSS) activity. The lead scientist will provide the instruments (or fabrication plans for instruments) in the array the host country will provide manpower, facilities, and operational support to obtain data with the instrument, located typically at a local university. This paper provides an overview of the IHY/UNBSS programme, its achievements and future plans.
Publisher: American Astronomical Society
Date: 16-10-2015
Publisher: American Astronomical Society
Date: 11-2013
Publisher: American Astronomical Society
Date: 06-09-2013
Publisher: American Astronomical Society
Date: 03-2003
DOI: 10.1086/346279
Publisher: American Astronomical Society
Date: 17-08-2020
Publisher: American Astronomical Society
Date: 17-07-2012
Publisher: American Astronomical Society
Date: 04-04-2013
Publisher: American Astronomical Society
Date: 14-02-2020
Publisher: Cambridge University Press (CUP)
Date: 08-2010
DOI: 10.1017/S1743921310003200
Abstract: We present the first results of a comprehensive HST study of the star-formation history of Fornax dSph, based on WFPC2 imaging of 7 Fornax fields. Our observations reach the oldest main-sequence turnoffs, allowing us to address fundamental questions of dwarf galaxy evolution, such as the spatial variations in the stellar content, and whether the old stellar population is made up of stars formed in a very early burst or the result of a more continuous star formation.
Publisher: American Astronomical Society
Date: 23-09-2015
Publisher: American Astronomical Society
Date: 15-06-2016
Publisher: Oxford University Press (OUP)
Date: 15-10-2010
Publisher: Oxford University Press (OUP)
Date: 11-01-2004
Publisher: American Astronomical Society
Date: 06-07-2012
Publisher: Oxford University Press (OUP)
Date: 11-02-2009
Publisher: EDP Sciences
Date: 07-2010
Publisher: American Astronomical Society
Date: 06-01-2021
Publisher: American Astronomical Society
Date: 22-11-2004
DOI: 10.1086/427388
Publisher: EDP Sciences
Date: 12-04-2011
Publisher: American Astronomical Society
Date: 24-08-2023
Abstract: We present the JWST Resolved Stellar Populations Early Release Science (ERS) program. We obtained 27.5 hr of NIRCam and NIRISS imaging of three targets in the Local Group (Milky Way globular cluster M92, ultrafaint dwarf galaxy Draco II , and star-forming dwarf galaxy WLM), which span factors of ∼10 5 in luminosity, ∼10 4 in distance, and ∼10 5 in surface brightness. We describe the survey strategy, scientific and technical goals, implementation details, present select NIRCam color–magnitude diagrams (CMDs), and validate the NIRCam exposure time calculator (ETC). Our CMDs are among the deepest in existence for each class of target. They touch the theoretical hydrogen-burning limit in M92 ( .08 M ⊙ M F090W ∼ +13.6), include the lowest-mass stars observed outside the Milky Way in Draco II (0.09 M ⊙ M F090W ∼ +12.1), and reach ∼1.5 mag below the oldest main-sequence turnoff in WLM ( M F090W ∼ +4.6). The PARSEC stellar models provide a good qualitative match to the NIRCam CMDs, though they are ∼0.05 mag too blue compared to M92 F090W − F150W data. Our CMDs show detector-dependent color offsets ranging from ∼0.02 mag in F090W – F150W to ∼0.1 mag in F277W – F444W these appear to be due to differences in the zero-point calibrations among the detectors. The NIRCam ETC (v2.0) matches the signal-to-noise ratios based on photon noise in uncrowded fields, but the ETC may not be accurate in more crowded fields, similar to what is known for the Hubble Space Telescope. We release the point-source photometry package DOLPHOT, optimized for NIRCam and NIRISS, for the community.
Publisher: Oxford University Press (OUP)
Date: 02-07-2012
Publisher: American Astronomical Society
Date: 10-03-2016
Publisher: Oxford University Press (OUP)
Date: 05-2013
DOI: 10.1093/MNRAS/STT655
Publisher: American Astronomical Society
Date: 23-02-2012
Publisher: American Astronomical Society
Date: 20-09-2001
DOI: 10.1086/323723
Publisher: American Astronomical Society
Date: 27-01-2014
Publisher: EDP Sciences
Date: 08-10-2009
Publisher: American Astronomical Society
Date: 08-03-2017
Publisher: American Astronomical Society
Date: 10-02-2002
DOI: 10.1086/337985
Publisher: American Astronomical Society
Date: 12-10-2011
Publisher: American Astronomical Society
Date: 23-04-2013
Publisher: American Astronomical Society
Date: 08-03-2010
Publisher: American Astronomical Society
Date: 28-01-2011
Publisher: American Astronomical Society
Date: 06-2002
DOI: 10.1086/340356
Publisher: American Astronomical Society
Date: 27-11-2017
Publisher: Oxford University Press (OUP)
Date: 11-11-2010
Publisher: Oxford University Press (OUP)
Date: 12-01-2018
DOI: 10.1093/MNRAS/STY087
Publisher: EDP Sciences
Date: 28-03-2012
Publisher: American Astronomical Society
Date: 02-03-2017
Publisher: American Astronomical Society
Date: 19-04-2023
Abstract: We measured the precise masses of the host and planet in the OGLE-2003-BLG-235 system, when the lens and source were resolving, with 2018 Keck high resolution images. This measurement is in agreement with the observation taken in 2005 with the Hubble Space Telescope (HST). In the 2005 data, the lens and sources were not resolved and the measurement was made using color-dependent centroid shift only. The Nancy Grace Roman Space Telescope will measure masses using data typically taken within 3–4 yr of the peak of the event, which is a much shorter baseline when compared to most of the mass measurements to date. Hence, the color-dependent centroid shift will be one of the primary methods of mass measurements for the Roman telescope. Yet, mass measurements of only two events (OGLE-2003-BLG-235 and OGLE-2005-BLG-071) have been done using the color-dependent centroid shift method so far. The accuracy of the measurements using this method are neither completely known nor well studied. The agreement of the Keck and HST results, as shown in this paper, is very important because this agreement confirms the accuracy of the mass measurements determined at a small lens-source separation using the color-dependent centroid shift method. It also shows that with high resolution images, the Roman telescope will be able to use color-dependent centroid shift at a 3–4 yr time baseline and produce mass measurements. We find that OGLE-2003-BLG-235 is a planetary system that consists of a 2.34 ± 0.43 M Jup planet orbiting a 0.56 ± 0.06 M ⊙ K-dwarf host star at a distance of 5.26 ± 0.71 kpc from the Sun.
Publisher: American Astronomical Society
Date: 25-03-2022
Abstract: Measurements of starlight polarized by aligned interstellar dust grains are used to probe the relation between the orientation of the ambient interstellar magnetic field (ISMF) and the ISMF traced by the ribbons of energetic neutral atoms discovered by the Interstellar Boundary Explorer spacecraft. We utilize polarization data, many acquired specifically for this study, to trace the configuration of the ISMF within 40 pc. A statistical analysis yields a best-fit ISMF orientation, B magpol , aligned with Galactic coordinates ℓ = 42°, b = 49°. Further analysis shows the ISMF is more orderly for “downfield” stars located over 90° from B magpol . The data subset of downfield stars yields an orientation for the nearby ISMF at ecliptic coordinates λ , β ≈ 219° ± 15°, 43° ± 9° (Galactic coordinates l , b ≈ 40°, 56°, ±17°). This best-fit ISMF orientation from polarization data is close to the field direction obtained from ribbon models. This agreement suggests that the ISMF shaping the heliosphere belongs to an extended ordered magnetic field. Extended filamentary structures are found throughout the sky. A previously discovered filament traversing the heliosphere nose region, “Filament A,” extends over 300° of the sky, and crosses the upwind direction of interstellar dust flowing into the heliosphere. Filament A overlaps the locations of the Voyager kilohertz emissions, three quasar intraday variables, cosmic microwave background (CMB) components, and the inflow direction of interstellar grains s led by Ulysses and Galileo. These features are likely located in the upstream outer heliosheath where ISMF drapes over the heliosphere, suggesting Filament A coincides with a dusty magnetized plasma. A filament 55° long is aligned with a possible shock interface between local interstellar clouds. A dark spot in the CMB is seen within 5° of the filament and within 10° of the downfield ISMF direction. Two large magnetic arcs are centered on the directions of the heliotail. The overlap between CMB components and the aligned dust grains forming Filament A indicates the configuration of dust entrained in the ISMF interacting with the heliosphere provides a measurable foreground to the CMB.
Publisher: American Astronomical Society
Date: 22-01-2018
Publisher: American Association for the Advancement of Science (AAAS)
Date: 18-08-2000
DOI: 10.1126/SCIENCE.289.5482.1149
Abstract: The Large Magellanic Cloud (LMC), a satellite of the Milky Way, is an important yardstick by which most intergalactic distances are measured. But as Cole explains in this Perspective, how far away the LMC is remains a matter of dispute, with far reaching implications in cosmology. But observations of Cepheids and of eclipsing binaries, two types of stars that allow absolute luminosity and thus absolute distances to be determined, are promising to resolve this important issue in the not too distant future.
Publisher: American Astronomical Society
Date: 13-04-2012
Publisher: Cambridge University Press (CUP)
Date: 07-2008
DOI: 10.1017/S174392130802855X
Abstract: We have obtained metallicities from near-infrared calcium triplet spectroscopy for nearly a thousand red giants in 28 fields spanning a range of radial distances from the center of the bar to near the tidal radius. We have used these data to investigate the radius-metallicity and age-metallicity relations. A powerful application of these data is in conjunction with the analysis of deep HST color–magnitude diagrams (CMDs). Most of the power in determining a robust star-formation history from a CMD comes from the main-sequence turnoff and subgiant branches. The age-metallicity degeneracy that results is largely broken by the red giant branch color, but theoretical model RGB colors remain uncertain. By incorporating the observed metallicity distribution function into the modelling process, a star-formation history with massively increased precision and accuracy can be derived. We incorporate the observed metallicity distribution of the LMC bar into a maximum-likelihood analysis of the bar CMD, and present a new star formation history and age–metallicity relation for the bar. The bar is certainly younger than the disk as a whole, and the most reliable estimates of its age are in the 5–6 Gyr range, when the mean gas abundance of the LMC had already increased to [Fe/H] ≳ −0.6. There is no obvious metallicity gradient among the old stars in the LMC disk out to a distance of 8–10 kpc, but the bar is more metal-rich than the disk by ≈0.1–0.2 dex. This is likely to be the result of the bar's younger average age. In both disk and bar, 95% of the red giants are more metal-rich than [Fe/H] = −1.2.
Publisher: Oxford University Press (OUP)
Date: 12-10-2017
Publisher: American Astronomical Society
Date: 17-11-2011
Publisher: Cambridge University Press (CUP)
Date: 06-2008
DOI: 10.1017/S174392130802499X
Abstract: Dwarf galaxies offer an opportunity to understand the properties of low metallicity star formation both today and at the earliest times at the epoch of the formation of the first stars. Here we concentrate on two galaxies in the Local Group: the dwarf irregular galaxy Leo A, which has been the recent target of deep HST/ACS imaging (Cole et al . 2007) and the Sculptor dwarf spheroidal, which has been the target of significant wide field spectroscopy with VLT/FLAMES (Battaglia 2007).
Publisher: American Astronomical Society
Date: 22-12-2016
Publisher: American Astronomical Society
Date: 17-08-2010
Publisher: American Astronomical Society
Date: 15-04-2014
Publisher: Oxford University Press (OUP)
Date: 08-08-2017
Publisher: American Astronomical Society
Date: 07-04-2014
Publisher: American Astronomical Society
Date: 26-10-2022
Abstract: We report new results for the gravitational microlensing target OGLE-2011-BLG-0950 from adaptive optics images using the Keck Observatory. The original analysis by Choi et al. and reanalysis by Suzuki et al. report degenerate solutions between planetary and stellar binary lens systems. This particular case is the most important type of degeneracy for exoplanet demographics because the distinction between a planetary mass or stellar binary companion has direct consequences for microlensing exoplanet statistics. The 8 and 10 yr baselines allow us to directly measure a relative proper motion of 4.20 ± 0.21 mas yr −1 , confirming the detection of the lens star system and ruling out the planetary companion models that predict a ∼4× smaller relative proper motion. The Keck data also rule out the wide stellar binary solution unless one of the components is a stellar remnant. The combination of the lens brightness and close stellar binary light-curve parameters yields primary and secondary star masses of M A = 1.12 − 0.09 + 0.11 and M B = 0.47 − 0.10 + 0.13 M ☉ at a distance of D L = 6.70 − 0.30 + 0.55 kpc and a projected separation of 0.39 − 0.04 + 0.05 au. Assuming that the predicted proper motions are measurably different, the high-resolution imaging method described here can be used to disentangle this degeneracy for events observed by the Roman exoplanet microlensing survey using Roman images taken near the beginning or end of the survey.
Publisher: American Astronomical Society
Date: 15-03-2007
DOI: 10.1086/516711
Publisher: American Astronomical Society
Date: 13-08-2012
Publisher: American Astronomical Society
Date: 05-10-2010
Publisher: American Astronomical Society
Date: 20-07-2002
DOI: 10.1086/342278
Publisher: American Astronomical Society
Date: 18-08-2010
Publisher: American Astronomical Society
Date: 16-05-2016
Publisher: American Astronomical Society
Date: 02-2012
Publisher: American Astronomical Society
Date: 07-01-2009
Publisher: Oxford University Press (OUP)
Date: 08-03-2013
DOI: 10.1093/MNRAS/STT165
Publisher: EDP Sciences
Date: 12-2013
Publisher: Springer Berlin Heidelberg
Date: 2009
Publisher: American Astronomical Society
Date: 16-09-2009
DOI: 10.1088/0004-637X/703/2/2082
Abstract: We analyze the extreme high-magnification microlensing event OGLE-2008-BLG-279, which peaked at a maximum magnification of A ∼ 1600 on 2008 May 30. The peak of this event exhibits both finite-source effects and terrestrial parallax, from which we determine the mass of the lens, M l = 0.64 ± 0.10 M ☉ , and its distance, D l = 4.0 ± 0.6 kpc. We rule out Jupiter-mass planetary companions to the lens star for projected separations in the range 0.5–20 AU. More generally, we find that this event was sensitive to planets with masses as small as with projected separations near the Einstein ring (∼3 AU).
Publisher: Springer Berlin Heidelberg
Date: 2009
Publisher: American Astronomical Society
Date: 30-05-2012
Publisher: American Astronomical Society
Date: 06-03-2018
Publisher: American Astronomical Society
Date: 19-12-2008
Publisher: Oxford University Press (OUP)
Date: 25-07-2017
Publisher: American Astronomical Society
Date: 08-09-2017
Publisher: American Astronomical Society
Date: 20-10-2016
Publisher: Springer Science and Business Media LLC
Date: 13-10-2021
Publisher: American Astronomical Society
Date: 28-04-2015
Publisher: American Astronomical Society
Date: 31-07-2012
Publisher: American Astronomical Society
Date: 27-04-2015
Publisher: American Astronomical Society
Date: 18-02-2010
Publisher: EDP Sciences
Date: 11-03-2011
Publisher: American Astronomical Society
Date: 07-2003
DOI: 10.1086/375761
Publisher: American Astronomical Society
Date: 20-06-2002
DOI: 10.1086/340769
Publisher: IOP Publishing
Date: 25-10-2016
Publisher: American Astronomical Society
Date: 19-09-2022
Abstract: We use globular cluster data from the Resolved Stellar Populations Early Release Science (ERS) program to validate the flux calibration for the Near Infrared Camera (NIRCam) on the James Webb Space Telescope. We find a significant flux offset between the eight short wavelength detectors, ranging from 1% to 23% (∼0.01–0.2 mag) that affects all NIRCam imaging observations. We deliver improved zero-points for the ERS filters and show that alternate zero-points derived by the community also improve the calibration significantly. We also find that the detector offsets appear to be time variable by up to at least 0.1 mag.
Publisher: American Astronomical Society
Date: 26-08-2011
Publisher: American Astronomical Society
Date: 20-09-1998
DOI: 10.1086/306169
Publisher: EDP Sciences
Date: 17-12-2012
Publisher: Cambridge University Press (CUP)
Date: 06-2008
DOI: 10.1017/S1743921308025118
Abstract: We introduce the SMC in space and time , a large coordinated space and ground-based program to study star formation processes and history, as well as variable stars, structure, kinematics and chemical evolution of the whole SMC. Here, we present the Colour-Magnitude Diagrams (CMDs) resulting from HST/ACS photometry, aimed at deriving the star formation history (SFH) in six fields of the SMC. The fields are located in the central regions, in the stellar halo, and in the wing toward the LMC. The CMDs are very deep, well beyond the oldest Main Sequence Turn-Off, and will allow us to derive the SFH over the entire Hubble time.
Publisher: Springer Science and Business Media LLC
Date: 11-2003
DOI: 10.1038/NATURE10684
Abstract: Most known extrasolar planets (exoplanets) have been discovered using the radial velocity or transit methods. Both are biased towards planets that are relatively close to their parent stars, and studies find that around 17-30% (refs 4, 5) of solar-like stars host a planet. Gravitational microlensing, on the other hand, probes planets that are further away from their stars. Recently, a population of planets that are unbound or very far from their stars was discovered by microlensing. These planets are at least as numerous as the stars in the Milky Way. Here we report a statistical analysis of microlensing data (gathered in 2002-07) that reveals the fraction of bound planets 0.5-10 AU (Sun-Earth distance) from their stars. We find that 17(+6)(-9)% of stars host Jupiter-mass planets (0.3-10 M(J), where M(J) = 318 M(⊕) and M(⊕) is Earth's mass). Cool Neptunes (10-30 M(⊕)) and super-Earths (5-10 M(⊕)) are even more common: their respective abundances per star are 52(+22)(-29)% and 62(+35)(-37)%. We conclude that stars are orbited by planets as a rule, rather than the exception.
Publisher: EDP Sciences
Date: 25-10-2012
Publisher: American Astronomical Society
Date: 25-06-2009
Publisher: American Astronomical Society
Date: 14-11-2012
Publisher: EDP Sciences
Date: 11-05-2011
Publisher: EDP Sciences
Date: 27-03-2013
Publisher: American Astronomical Society
Date: 27-11-2013
Publisher: American Astronomical Society
Date: 15-02-2023
Abstract: We present criteria for separately classifying stars and unresolved background galaxies in photometric catalogs generated with the point-spread function fitting photometry software DOLPHOT from images taken of Draco II, WLM, and M92 with the Near Infrared Camera (NIRCam) on JWST. Photometric quality metrics from DOLPHOT in one or two filters can recover a pure s le of stars. Conversely, colors formed between short-wavelength and long-wavelength filters can be used to effectively identify pure s les of galaxies. Our results highlight that the existing DOLPHOT output parameters can be used to reliably classify stars in our NIRCam data without the need to resort to external tools or more complex heuristics.
Publisher: EDP Sciences
Date: 09-01-2008
Publisher: American Astronomical Society
Date: 20-03-2006
DOI: 10.1086/499914
Publisher: Cambridge University Press (CUP)
Date: 12-2007
Publisher: Oxford University Press (OUP)
Date: 16-06-2014
DOI: 10.1093/MNRAS/STU910
Publisher: Cambridge University Press (CUP)
Date: 07-2008
DOI: 10.1017/S1743921308028597
Abstract: We have carried out a large-scale investigation of the metallicity and kinematics for a number of LMC and SMC star clusters using Ca ii triplet spectra obtained at the VLT . Our s le includes 28 LMC and 16 SMC clusters, covering a wide range of ages and spatial extent of the host galaxy. We determine mean cluster velocities to about 2 km s −1 and metallicities to 0.05 dex (random error), from about 7 members per cluster. Herein we present the main results for this study for the cluster metallicity distributions, metallicity gradients, age-metallicity relations and kinematics.
Publisher: American Astronomical Society
Date: 17-01-2013
Publisher: American Astronomical Society
Date: 06-05-2013
Publisher: American Astronomical Society
Date: 07-04-2008
DOI: 10.1086/588285
Publisher: Cambridge University Press (CUP)
Date: 08-2006
DOI: 10.1017/S1743921306005278
Abstract: We present results from a project aimed at better understanding the kinematics and metallicities of populous clusters in the LMC. In an effort to update previous [Fe/H] determinations, we have utilized FORS2 on the VLT to obtain infrared spectra for more than 200 stars in 28 LMC clusters. The absorption lines of the calcium II triplet were then used to calculate radial velocities and [Fe/H] for a s le of clusters spanning a large range of ages (~ 1-13 Gyr) and metallicities (−0.3 [ Fe / H ] − 2.0). We determine mean cluster velocities to typically 1.6 km s −1 and mean metallicities to 0.04 dex (random error). For eight of these clusters, we report the first spectroscopically determined metallicities based on in idual cluster stars, and six of these eight have no published radial velocity measurements. Combining our data with archival HST/WFPC2 photometry, we find the newly measured cluster, NGC 1718, is one of the most metal-poor ([Fe/H] ~ −0.80), intermediate age (~ 2 Gyr) inner disk clusters in the LMC. Similar to what was found by previous authors, this cluster s le has motions consistent with that of a single rotating disk system, with no indication that the newly reported clusters exhibit halo kinematics. Additionally, our findings confirm previous results which show that the LMC lacks the metallicity gradient typically seen in non-barred spiral galaxies, suggesting that the bar is driving the mixing of stellar populations in the LMC. However, in contrast to previous work, we find that the higher metallicity clusters (≥−1.0 dex) in our s le show a very tight distribution (mean [Fe/H] = −0.48, σ = 0.09), with no tail toward solar metallicities. The cluster distribution is similar to what has been found for red giant stars in the bar, which indicates that the bar and the intermediate age clusters have similar star formation histories. This is in good agreement with recent theoretical models that suggest the bar and intermediate age clusters formed as a result of a close encounter with the SMC ~ 4 Gyr ago.
Publisher: American Astronomical Society
Date: 07-2022
Abstract: We report the first unambiguous detection and mass measurement of an isolated stellar-mass black hole (BH). We used the Hubble Space Telescope (HST) to carry out precise astrometry of the source star of the long-duration ( t E ≃ 270 days), high-magnification microlensing event MOA-2011-BLG-191/OGLE-2011-BLG-0462 (hereafter designated as MOA-11-191/OGLE-11-462), in the direction of the Galactic bulge. HST imaging, conducted at eight epochs over an interval of 6 yr, reveals a clear relativistic astrometric deflection of the background star’s apparent position. Ground-based photometry of MOA-11-191/OGLE-11-462 shows a parallactic signature of the effect of Earth’s motion on the microlensing light curve. Combining the HST astrometry with the ground-based light curve and the derived parallax, we obtain a lens mass of 7.1 ± 1.3 M ⊙ and a distance of 1.58 ± 0.18 kpc. We show that the lens emits no detectable light, which, along with having a mass higher than is possible for a white dwarf or neutron star, confirms its BH nature. Our analysis also provides an absolute proper motion for the BH. The proper motion is offset from the mean motion of Galactic disk stars at similar distances by an amount corresponding to a transverse space velocity of ∼45 km s −1 , suggesting that the BH received a “natal kick” from its supernova explosion. Previous mass determinations for stellar-mass BHs have come from radial velocity measurements of Galactic X-ray binaries and from gravitational radiation emitted by merging BHs in binary systems in external galaxies. Our mass measurement is the first for an isolated stellar-mass BH using any technique.
Publisher: American Astronomical Society
Date: 09-2009
Publisher: American Astronomical Society
Date: 10-06-2009
Publisher: American Astronomical Society
Date: 24-02-2011
Publisher: American Astronomical Society
Date: 10-10-2003
DOI: 10.1086/377635
Publisher: American Astronomical Society
Date: 19-06-2009
Publisher: EDP Sciences
Date: 27-11-2012
Publisher: American Astronomical Society
Date: 03-2005
DOI: 10.1086/428007
Publisher: American Astronomical Society
Date: 02-05-2012
Publisher: American Astronomical Society
Date: 23-01-2020
Publisher: American Astronomical Society
Date: 10-2023
Publisher: Oxford University Press (OUP)
Date: 24-08-2018
Publisher: EDP Sciences
Date: 04-2009
Publisher: Oxford University Press (OUP)
Date: 18-11-2015
Publisher: Oxford University Press (OUP)
Date: 15-01-2016
Publisher: Oxford University Press (OUP)
Date: 16-06-2014
DOI: 10.1093/MNRAS/STU926
Publisher: American Astronomical Society
Date: 13-10-2014
Publisher: American Astronomical Society
Date: 12-09-2006
DOI: 10.1086/507303
Publisher: American Astronomical Society
Date: 08-01-2013
Publisher: Cambridge University Press (CUP)
Date: 2010
DOI: 10.1071/AS09066
Abstract: In this review I summarise recent advances in our understanding of the importance of starburst events to the evolutionary histories of nearby galaxies. Ongoing bursts are easily diagnosed in emission-line surveys, but assessing the timing and intensity of fossil bursts requires more effort, usually demanding color–magnitude diagrams or spectroscopy of in idual stars. For ages older than ∼1 Gyr, this type of observation is currently limited to the Local Group and its immediate surroundings. However, if the Local Volume is representative of the Universe as a whole, then studies of the age and metallicity distributions of star clusters and resolved stellar populations should give statistical clues as to the frequency and importance of bursts to the histories of galaxies in general. Based on starburst statistics in the literature and synthetic colour-magnitude diagram studies of Local Group galaxies, I attempt to distinguish between systemic starbursts that strongly impact galaxy evolution and stochastic bursts that can appear impressive but are ultimately of little significance on gigayear timescales. As a specific case, it appears as though IC 10, the only starburst galaxy in the Local Group, falls into the latter category and is not fundamentally different from other nearby dwarf irregular galaxies.
Publisher: American Astronomical Society
Date: 02-2002
DOI: 10.1086/324635
Publisher: American Astronomical Society
Date: 08-03-2016
Start Date: 02-2011
End Date: 03-2014
Amount: $275,000.00
Funder: Australian Research Council
View Funded ActivityStart Date: 2020
End Date: 11-2024
Amount: $465,000.00
Funder: Australian Research Council
View Funded Activity