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Near-Infrared Spectroscopy of Two Galaxies at z=2.3 and z=2.9: New Probes of Chemical and Dynamical Evolution at High Redshift
This study presents Keck optical and infrared spectroscopy of therest-frame ultraviolet and optical emission lines in twoLyα-emitting galaxies at z>2. These data provide insight on theevolution of fundamental galaxy scaling relations at early epochs,especially the luminosity-velocity and luminosity-metallicity relations.Spectral diagnostics suggest that the Coup Fourré galaxy at z=2.3and Lynx 2-9691, a serendipitously discovered, luminous Lyman dropgalaxy at z=2.9, are star-forming galaxies without active nuclei. Lynx2-9691 exhibits extended [O III] emission over a diameter of greaterthan 28 kpc, reminiscent of the Lyα nebulae discovered near Lymandrop galaxies. We estimate star formation rates of 59 and 111Msolar yr-1, respectively, from Balmerrecombination line luminosities, 2-3 times higher than inferred from theultraviolet continuum. The ratios of strong nebular emission linesindicate subsolar oxygen abundances in the range8.2<12+log(O/H)<8.8 (Z=0.25-0.95 Zsolar).Interestingly, Galactic metal-rich globular clusters have similarmetallicities, consistent with the idea that we could be seeing theformation of galaxies like the Milky Way at z~3. The measured gas-phaseoxygen abundances are greater than 4-10 times higher than the Z<0.1Zsolar metallicities found in damped Lyα (DLA)absorbers at similar redshifts, indicating that DLA systems tracefundamentally different environments than the vigorously star-formingobjects observed here. If this intense star formation activityrepresents the dominant formation episodes for stars in today's spiralbulges or ellipticals, then the evolved descendants in the localuniverse should exhibit similarly subsolar metallicities in theirdominant stellar populations that formed 8-10 Gyr ago. When these newdata are combined with a sample of four other high-redshiftspectroscopic results from the literature, we find that star-forminggalaxies at z~3 are 2-4 mag more luminous than local spiral galaxies ofsimilar metallicity and thus are offset from the localluminosity-metallicity relation. Their kinematic line widths areσv=65-130 km s-1, making this sample 1-3 magmore luminous than local galaxies of similar line width and mass. Lessluminous Lyman drop galaxies need to be studied to see if thesedeviations are universal or apply to only the most luminoushigh-redshift galaxies. Based on observations obtained at the W. M. KeckObservatory, which is operated jointly by the University of Californiaand the California Institute of Technology.
| Classification of Population II Stars in the Vilnius Photometric System. II. Results
The results of photometric classification of 848 true and suspectedPopulation II stars, some of which were found to belong to Population I,are presented. The stars were classified using a new calibrationdescribed in Paper I (Bartkevicius & Lazauskaite 1996). We combinethese results with our results from Paper I and discuss in greaterdetail the following groups of stars: UU Herculis-type stars and otherhigh-galactic-latitude supergiants, field red horizontal-branch stars,metal-deficient visual binaries, metal-deficient subgiants, stars fromthe Catalogue of Metal-deficient F--M Stars Classified Photometrically(MDPH; Bartkevicius 1993) and stars from one of the HIPPARCOS programs(Bartkevicius 1994a). It is confirmed that high galactic latitudesupergiants from the Bartaya (1979) catalog are giants or even dwarfs.Some stars, identified by Rose (1985) and Tautvaisiene (1996a) as fieldRHB stars, appear to be ordinary giants according to our classification.Some of the visual binaries studied can be considered as physical pairs.Quite a large fraction of stars from the MDPH catalog are found to havesolar metallicity. A number of new possible UU Herculis-type stars, RHBstars and metal-deficient subgiants are identified.
| Photoelectric Photometry of Metal-Poor and Other Peculiar Stars in the Vilnius System
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Osservazione e dati astrometrici
| Costellazione: | Giraffa |
| Ascensione retta: | 05h05m30.76s |
| Declinazione: | +52°48'36.6" |
| Magnitudine apparente: | 9.97 |
| Distanza: | 45.767 parsec |
| Moto proprio RA: | 13.7 |
| Moto proprio Dec: | -94 |
| B-T magnitude: | 11.245 |
| V-T magnitude: | 10.076 |
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