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Gemini Near Infrared Spectrograph Observations of the Central Supermassive Black Hole in Centaurus A
Gebhardt, Karl; Richstone, Douglas; Bergmann, Marcel +1 more
The Gemini Near Infrared Spectrograph on Gemini South unlocks new possibilities to study the central black holes (BHs) in dusty galaxies that have been inaccessible to previous BH studies. We exploit good near-infrared seeing to measure the central BH of Centaurus A (NGC 5128). We measure the stellar kinematics of NGC 5128 using the region around …
A Change in the Physical State of η Carinae?
Weis, K.; Stahl, O.; Davidson, K. +8 more
During η Car's spectroscopic event in mid-2003, the stellar wind's bright Hα and Hβ emission lines temporarily had a distinctive shape unlike that reported on any previous occasion and particularly unlike the 1997-1998 event. Evidently the structure of the wind changed between 1997 and 2003. Combining this with other evidence, we suspect that the …
RX J0152.7-1357: Stellar Populations in an X-Ray Luminous Galaxy Cluster at z = 0.83
Crampton, David; Jørgensen, Inger; Takamiya, Marianne +3 more
We present a study of the stellar populations of galaxies in the cluster RX J0152.7-1357 at a redshift of 0.83. The study is based on new high signal-to-noise ratio spectroscopy of 29 cluster members covering the wavelength range 5000-10000 Å, as well as r'i'z' photometry of the cluster. We use scaling relations be…
The Metallicity Distribution Function of Field Stars in M31's Bulge
Sarajedini, Ata; Jablonka, Pascale
We have used Hubble Space Telescope Wide Field Planetary Camera 2 observations to construct a color-magnitude diagram (CMD) for the bulge of M31 at a location ~1.6 kpc from the galaxy's center. Using scaled solar abundance theoretical red giant branches with a range of metallicities, we have translated the observed colors of the stars in the CMD t…
Thermal Dust Emission from Proplyds, Unresolved Disks, and Shocks in the Orion Nebula
Smith, Nathan; Bally, John; Kassis, Marc +2 more
We present a new 11.7 µm mosaic image of the inner Orion Nebula obtained with the T-ReCS instrument on Gemini South. The map covers 2.7 arcmin 7×1.6 arcmin, with a diffraction-limited spatial resolution of 0.35" it includes the BN/KL region, the Trapezium, and OMC-1 South. Excluding BN/KL, we detect 91 thermal-IR point sources, with 27 known…
The Structural Properties of Isolated Galaxies, Spiral-Spiral Pairs, and Mergers: The Robustness of Galaxy Morphology during Secular Evolution
Conselice, C. J.; Hernández-Toledo, H. M.; Avila-Reese, V. +1 more
We present a structural analysis of nearby galaxies in spiral-spiral pairs in optical BVRI bands and compare them with the structures of isolated spiral galaxies and galaxies in ongoing mergers. We use these comparisons to determine how galaxy structure changes during galaxy interactions and mergers. We analyze light concentration (C), asymmetry (…
Old Globular Clusters Masquerading as Young in NGC 4365?
Forbes, Duncan A.; Brodie, Jean P.; Beasley, Michael A. +5 more
High signal-to-noise ratio, low-resolution spectra have been obtained for 22 globular clusters (GCs) in NGC 4365. Some of these were selected as probable representatives of an intermediate-age (2-5 Gyr), extremely metal-rich GC subpopulation. The presence of such a subpopulation had been inferred from the unusual optical and near-infrared color di…
On the Stellar Populations in NGC 185 and NGC 205 and the Nuclear Star Cluster in NGC 205 from Hubble Space Telescope Observations
Martínez-Delgado, D.; Butler, D. J.
We present the first detailed analysis of resolved stellar populations in the dwarf galaxies NGC 185 and NGC 205 based on archival V- and I-band WFPC2 pointings. For NGC 185 we deduce from the brightest main-sequence and blue-loop stars that star formation was probably still active about 4×108 yr ago and have three key abundance-related…
Color-Magnitude Diagrams and Luminosity Functions Down to the Hydrogen-Burning Limit. III. A Preliminary Hubble Space Telescope Study of NGC 6791
Anderson, Jay; Bedin, Luigi R.; Piotto, Giampaolo +2 more
Using Hubble Space Telescope Advanced Camera for Surveys Wide Field Channel images, we derive the color-magnitude diagram of the old, metal-rich open cluster NGC 6791 to nearly 29th magnitude in V, which is the neighborhood of the hydrogen-burning limit. Comparison with isochrones leads to a discussion of the distance modulus, the reddening, and t…
Massive Young Clusters in the Disk of M31
Bellazzini, M.; Galleti, S.; Federici, L. +3 more
We have studied the properties of a sample of 67 very blue and likely young massive clusters in M31 extracted from the Bologna Revised Catalog of globular clusters, selected according to their color [(B-V)0<=0.45] and/or the strength of their Hβ spectral index (Hβ>=3.5 Å). Their existence in M31 has been noted by several authors i…