Browsing by Author "Jerjen, H"

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    Discovery of a high-redshift Einstein ring
    (2005) Cabanac, RA; Valls-Gabaud, D; Jaunsen, AO; Lidman, C; Jerjen, H
    We report the discovery of a partial Einstein ring of radius 1.''48 produced by a massive (and seemingly isolated) elliptical galaxy. The spectroscopic follow-up at the VLT reveals a 2L(star) galaxy at z = 0.986, which is lensing a post-starburst galaxy at z = 3.773. This unique configuration yields a very precise measure of the mass of the lens within the Einstein radius, (8.3 +/- 0.4) x 10(11)h(70)(-1) M-circle dot. The fundamental plane relation indicates an evolution rate of dlog(M/L)(B)/dz = -0.57 +/- 0.04, similar to other massive ellipticals at this redshift. The source galaxy shows strong interstellar absorption lines indicative of large gas-phase metallicities, with fading st phase populations after a burst stellar Higher resolution spectra and will allow the detailed imaging study of an unbiased representative of the galaxy population when the universe was just 12% of its current age.
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    Tip of the red giant branch distance for the Sculptor group dwarf ESO 540-032
    (2001) Jerjen, H; Rejkuba, M
    We present the first VI CCD photometry for the Sculptor group galaxy ESO 540-032 obtained at the Very Large Telescope UT1+FORS1. The (I, V - I) colour-magnitude diagram indicates that this intermediate-type dwarf galaxy is dominated by old, metal-poor ([Fe/H] approximate to -1.7 dex) stars, with a small population of slightly more metal-rich ([Fe/H] approximate to -1.3 dex), young (age 150-500 Myr) stars. A discontinuity in the I-band luminosity function is detected at I-0 = 23.44 +/-0.09 mag. Interpreting this feature as the tip of the red giant branch and adopting M-I = -4.20 +/-0.10 mag for its absolute magnitude, we have determined a Population II distance modulus of (m - M)(0) = 27.64 +/-0.14 mag (3.4 +/-0.2 Mpc). This distance confirms ESO 540-032 as a member of the nearby Sculptor group but is significantly larger than a previously reported value based on the Surface Brightness Fluctuation (SBF) method. The results from stellar population synthesis models suggest that the application of the SBF technique on dwarf galaxies with mixed morphology requires a detailed knowledge of the underlying stellar composition and thus offers no advantage over a direct distance measurement using the tip of the red giant branch as distance indicator. We produce the surface brightness profiles for ESO 540-032 and derive the photometric and structural parameters. The global properties follow closely the relations between metallicity and both absolute magnitude and central surface brightness defined by dwarf elliptical galaxies in the Local Group. Finally, we identify and discuss a non-stellar object near the galaxy center which may resemble a globular cluster.