We have been awarded a NASA grant to obtain followup photometry (and spectroscopy) of the Grid Giant Star Survey (GGSS) candidates we are establishing in our Space Interferometry Mission (SIM) Preparatory Science program. The GGSS will... more
We have been awarded a NASA grant to obtain followup photometry (and spectroscopy) of the Grid Giant Star Survey (GGSS) candidates we are establishing in our Space Interferometry Mission (SIM) Preparatory Science program. The GGSS will yield ~ 4000 metal-poor G-K giants as SIM Astrometric Grid candidates, based on single-epoch photometry and low resolution spectroscopy. Multi-epoch photometric followup observations of
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The Grid Giant Star Survey (GGSS) is a partially-filled, all-sky survey for metal-poor K giants as potential constituents of the Astrometric Grid for the Space Interferometry Mission (SIM). The goal of the GGSS is to find the most distant... more
The Grid Giant Star Survey (GGSS) is a partially-filled, all-sky survey for metal-poor K giants as potential constituents of the Astrometric Grid for the Space Interferometry Mission (SIM). The goal of the GGSS is to find the most distant K giants possible -- in order to minimize effects of binary companions, large planets, starspotting, and flaring on stability of astrometric
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We present a preliminary result of a modern CCD survey of M31 globular clusters (GCs) for ˜ 3^o × 3^o area centered on M31. Previous CCD surveys were performed only for small areas of M31, and our study is the first systematic GC survey... more
We present a preliminary result of a modern CCD survey of M31 globular clusters (GCs) for ˜ 3^o × 3^o area centered on M31. Previous CCD surveys were performed only for small areas of M31, and our study is the first systematic GC survey for a wide area of this galaxy. We have obtained optical spectra for the photometric GC candidates by using the KPNO/WIYN 3.5 m telescope and Hydra multifiber spectrograph to confirm membership in M31. We have found 126 new GCs and ˜ 500 new GC candidates together with 544 previously known GCs. We have plotted reddening-corrected (C-T_1)_0 color distributions and shown that the two-component Gaussian fitting is well matched. This is the first study which shows clear bimodality in the M31 GC color distribution.
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We have been awarded a NASA grant to obtain followup photometry and spectroscopy of the Grid Giant Star Survey (GGSS) candidates we are establishing in our Space Interferometry Mission (SIM) Preparatory Science program. The GGSS will... more
We have been awarded a NASA grant to obtain followup photometry and spectroscopy of the Grid Giant Star Survey (GGSS) candidates we are establishing in our Space Interferometry Mission (SIM) Preparatory Science program. The GGSS will yield ~ 4000 metal-poor G-K giants as SIM Astrometric Grid candidates, based on single-epoch photometry and low resolution spectroscopy. Multi-epoch photometric followup observations of
Research Interests:
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We show our results on followup photometry and spectroscopy of the Grid Giant Star Survey (GGSS) candidates we are establishing in our Space Interferometry Mission (SIM) Preparatory Science program. The GGSS has established thousands of... more
We show our results on followup photometry and spectroscopy of the Grid Giant Star Survey (GGSS) candidates we are establishing in our Space Interferometry Mission (SIM) Preparatory Science program. The GGSS has established thousands of metal-poor giants as SIM Astrometric Grid candidates, based on single-epoch photometric and low resolution spectroscopic observations. Metal-poor G-K giant stars are excellent Grid Candidates because,
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The Grid Giant Star Survey (GGSS) is a partially-filled, all-sky survey for metal-poor K giants as potential constituents of the Astrometric Grid for the Space Interferometry Mission (SIM). The goal of the GGSS is to find the most distant... more
The Grid Giant Star Survey (GGSS) is a partially-filled, all-sky survey for metal-poor K giants as potential constituents of the Astrometric Grid for the Space Interferometry Mission (SIM). The goal of the GGSS is to find the most distant K giants possible -- in order to minimize effects of binary companions, large planets, starspotting, and flaring on stability of astrometric
Research Interests:
We have been awarded a NASA grant to obtain followup photometry of the Grid Giant Star Survey (GGSS) candidates we are establishing in our Space Interferometry Mission (SIM) Preparatory Science program. The GGSS will yield ~ 4000... more
We have been awarded a NASA grant to obtain followup photometry of the Grid Giant Star Survey (GGSS) candidates we are establishing in our Space Interferometry Mission (SIM) Preparatory Science program. The GGSS will yield ~ 4000 metal-poor G-K giants as SIM Astrometric Grid candidates, based on single-epoch photometry and low resolution spectroscopy. %(being obtained at LCO). Multi-epoch photometric followup observations of these candidates are essential for verifying their photometric stability and thus guaranteeing their utility as SIM Grid stars. We propose here to continue our followup photometric observations which started in late 2000. These data are not only critical for the SIM project but will also allow us to improve our very limited knowledge of binary and planetary frequency in metal-poor giants. Because the kinematic properties of these stars will eventually be determined to unprecedented accuracy, a detailed understanding of their characteristics will not only be impo...
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The 10 SMC cluster fields were observed during four nights with the Cerro Tololo Inter-American Observatory (CTIO) 0.9-m telescope in 2002 October and 2003 December, with filters of the Washington photometric system (C and T1, effective... more
The 10 SMC cluster fields were observed during four nights with the Cerro Tololo Inter-American Observatory (CTIO) 0.9-m telescope in 2002 October and 2003 December, with filters of the Washington photometric system (C and T1, effective wavelength 391 and 633nm) (11 data files).
We present a preliminary result of a modern CCD survey of M31 globular clusters (GCs) for ˜ 3^o × 3^o area centered on M31. Previous CCD surveys were performed only for small areas of M31, and our study is the first systematic GC survey... more
We present a preliminary result of a modern CCD survey of M31 globular clusters (GCs) for ˜ 3^o × 3^o area centered on M31. Previous CCD surveys were performed only for small areas of M31, and our study is the first systematic GC survey for a wide area of this galaxy. We have obtained optical spectra for the photometric GC candidates by using the KPNO/WIYN 3.5 m telescope and Hydra multifiber spectrograph to confirm membership in M31. We have found 126 new GCs and ˜ 500 new GC candidates together with 544 previously known GCs. We have plotted reddening-corrected (C-T_1)_0 color distributions and shown that the two-component Gaussian fitting is well matched. This is the first study which shows clear bimodality in the M31 GC color distribution.
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The Nearby Galaxies Supernova Search (NGSS) campaigns have successfully discovered ~25 supernovae and strong supernovae candidates over the past 2 years. However, to obtain accurate statistics such as SN rates, it is important to know the... more
The Nearby Galaxies Supernova Search (NGSS) campaigns have successfully discovered ~25 supernovae and strong supernovae candidates over the past 2 years. However, to obtain accurate statistics such as SN rates, it is important to know the depth to which we can efficiently detect objects, and thus the effective limiting magnitudes of the campaigns. We have begun this analysis by conducting
We have performed a new systematic globular cluster (GC) survey of M31 for 3 3 area centered on M31. Using photometric data obtained from observations using the KPNO 0.9-m telescope + Washington CMT1 lters, and spectroscopic data obtained... more
We have performed a new systematic globular cluster (GC) survey of M31 for 3 3 area centered on M31. Using photometric data obtained from observations using the KPNO 0.9-m telescope + Washington CMT1 lters, and spectroscopic data obtained from observations using the KPNO/WIYN 3.5-m telescope + Hydra multib er spectrograph, we have conrmed 544 previously known GCs and found over 600 new GCs and candidates, of which more than one hundred are believed to be genuine GCs. We present the metallicity distribution of the previously known and new GCs in M31, which is better t with three components than with two components.
To perform wide-angle astrometry of stars to an accuracy of 4 mu as, NASA's Space Interferometry Mission (SIM) requires an astrometrically stable reference frame composed of relatively bright stars... more
To perform wide-angle astrometry of stars to an accuracy of 4 mu as, NASA's Space Interferometry Mission (SIM) requires an astrometrically stable reference frame composed of relatively bright stars (V<13), the ``Astrometric Grid''. Low metal-abundance K giants are good candidate stars for the SIM Astrometric Grid because they are the most distant stars brighter than V=13 that are also common
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We present a progress report on Washington photometry of several hundred new globular cluster (GC) candidates in M31 which were recently found from our new CCD survey of GCs. The Washington CMT1 filters that we used are very efficient to... more
We present a progress report on Washington photometry of several hundred new globular cluster (GC) candidates in M31 which were recently found from our new CCD survey of GCs. The Washington CMT1 filters that we used are very efficient to survey extragalactic GCs and to estimate the metallicity of GCs. Preliminary color-magnitude diagrams and color-color diagrams of the new GC candidates and known GCs in M31 are obtained.
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Searching for globular cluster candidates in nearby galaxies such as M31 is the first step to study the characteristics of extragalactic globular cluster systems. Previous searches for M31 globular clusters were mostly based on visual... more
Searching for globular cluster candidates in nearby galaxies such as M31 is the first step to study the characteristics of extragalactic globular cluster systems. Previous searches for M31 globular clusters were mostly based on visual inspection of photograpic plates. We have selected globular cluster candidates from a wide-field Washington CCD survey of M31, using various methods: color-magnitude diagrams, color-color diagrams, point spread function subtraction and visual inspection of the objects. The efficiency and accuracy of these methods for finding globular clusters are presented.
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We present a progress report of our wide field CCD survey of globular clusters in M31. We have covered a 3 deg × 3 deg area centered on M31, using the KPNO 0.9m and Washington CMT1 filters. Our survey is much deeper and more sensitive... more
We present a progress report of our wide field CCD survey of globular clusters in M31. We have covered a 3 deg × 3 deg area centered on M31, using the KPNO 0.9m and Washington CMT1 filters. Our survey is much deeper and more sensitive than previous surveys. We have found several hundred new globular cluster candidates in M31 in addition to confirming previously known globular clusters, and also have found a number of interlopers among previous globular cluster catalogs. We have also obtained spectra of about 500 objects among these candidates using HYDRA at the WIYN 3.5m telescope, which are used for classification and measuring the radial velocity of the candidate objects. When completed, a new master catalog of globular clusters in M31 will be made, combining the new globular clusters with the known globular clusters.
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NASA’s Space Interferometry Mission (SIM), scheduled for launch in 2009, will determine the positions of thousands of stars as faint as V = 20 to a precision better than 4 microarcseconds (µas). A key part of the mission is the... more
NASA’s Space Interferometry Mission (SIM), scheduled for launch in 2009, will determine the positions of thousands of stars as faint as V = 20 to a precision better than 4 microarcseconds (µas). A key part of the mission is the Astrometric Grid, which is a reference frame of several thousand stars with V ≤ 13 against which all relative measurements will be calibrated. To serve as a reliable inertial reference frame, the Grid must be astrometrically stable against photocenter jitter (from planets, binary companions, flaring or spotting) at the ~ 4µas level. Sub–solar metallicity giant stars, by virtue of their intrinsic luminosity, can probe the Galaxy to greater distances than almost any other stellar type at the same apparent magnitude. Thus, distant…
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ABSTRACT
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To perform wide-angle astrometry, SIM requires an astrometrically stable, precision reference frame of stars, the Astrometric Grid. The Grid must be composed of relatively bright stars (V < ~ 13) to minimize impact on SIM's... more
To perform wide-angle astrometry, SIM requires an astrometrically stable, precision reference frame of stars, the Astrometric Grid. The Grid must be composed of relatively bright stars (V < ~ 13) to minimize impact on SIM's observing schedule. Subsolar metallicity K giants are good candidate stars for the SIM Astrometric Grid, because they are both relatively common at V < ~ 13 and because they are luminous and therefore distant, so that any problems related to astrometric jitter (from large planets, starspotting, and flaring) is minimized. The goal of the GGSS is to discover the most distant metal-poor K giants in 1306 ``bricks'', each covering ~0.5 deg2 at a mean separation of ~6o, distributed over the entire sky. To date, photometric observations with the Washington M, T2 and the (gravity sensitive) DDO51 filters have been performed in 880 bricks at the Las Campanas 1-m Swope telescope and the 0.8-m telescope of McDonald Observatory. Semi-automated reduction pipelines generate a sample of giant candidates, along with photometric parallaxes and metallicities derived from the three-filter system. In each brick, up to four candidate Grid stars are selected as those K giants with M<13.5 having the largest distances. Preliminary results show that 93% of bricks have at least one Grid candidate, with median photometric distance and metallicity of d ~ 3.6 kpc and [Fe/H] ~ -1.0, respectively. Follow-up, low resolution spectroscopy enables us to verify the luminosity class and determine spectroscopic abundances and radial velocities of the candidate giants. At present, we have obtained spectra of over 1600 Grid candidates in the wavelength range 4800 -- 6800 Å by using the Modular Spectrograph on the Swope telescope. Here we present preliminary results of the GGSS and discuss several checks on the derived photometric properties of the Grid candidates.
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Previous surveys for M31 globular clusters (GCs) have been mainly done by using photographic plates. We have performed a new systematic survey for M31 GCs using imaging by KPNO 0.9 m telescope + 2K CCD + C,Ms, T 1 filters, and... more
Previous surveys for M31 globular clusters (GCs) have been mainly done by using photographic plates. We have performed a new systematic survey for M31 GCs using imaging by KPNO 0.9 m telescope + 2K CCD + C,Ms, T 1 filters, and spectroscopy by WIYN 3.5 m telescope + Hydra multifiber spectrograph.
ABSTRACT
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IAUC 7524 available at Central Bureau for Astronomical Telegrams.
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The Nearby Galaxies Supernova Search (NGSS) campaigns have successfully discovered ~25 supernovae and strong supernovae candidates over the past 2 years. However, to obtain accurate statistics such as SN rates, it is important to know the... more
The Nearby Galaxies Supernova Search (NGSS) campaigns have successfully discovered ~25 supernovae and strong supernovae candidates over the past 2 years. However, to obtain accurate statistics such as SN rates, it is important to know the depth to which we can efficiently detect objects, and thus the effective limiting magnitudes of the campaigns. We have begun this analysis by conducting
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To perform wide-angle astrometry, SIM requires an astrometrically stable, precision reference frame of stars, the Astrometric Grid. The Grid must be composed of relatively bright stars (V < ~ 13) to minimize impact on SIM's... more
To perform wide-angle astrometry, SIM requires an astrometrically stable, precision reference frame of stars, the Astrometric Grid. The Grid must be composed of relatively bright stars (V < ~ 13) to minimize impact on SIM's observing schedule. Subsolar metallicity K giants are good candidate stars for the SIM Astrometric Grid, because they are both relatively common at V < ~ 13 and because they are luminous and therefore distant, so that any problems related to astrometric jitter (from large planets, starspotting, and flaring) is minimized. The goal of the GGSS is to discover the most distant metal-poor K giants in 1306 ``bricks'', each covering ~0.5 deg2 at a mean separation of ~6o, distributed over the entire sky. To date, photometric observations with the Washington M, T2 and the (gravity sensitive) DDO51 filters have been performed in 880 bricks at the Las Campanas 1-m Swope telescope and the 0.8-m telescope of McDonald Observatory. Semi-automated reduction ...