| 1. |
- Bufano, Filomena, et al.
(författare)
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THE HIGHLY ENERGETIC EXPANSION OF SN 2010bh ASSOCIATED WITH GRB 100316D
- 2012
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Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 753:1, s. 67-
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Tidskriftsartikel (refereegranskat)abstract
- We present the spectroscopic and photometric evolution of the nearby (z = 0.059) spectroscopically confirmed Type Ic supernova, SN 2010bh, associated with the soft, long-duration gamma-ray burst (X-ray flash) GRB 100316D. Intensive follow-up observations of SN 2010bh were performed at the ESO Very Large Telescope (VLT) using the X-shooter and FORS2 instruments. Thanks to the detailed temporal coverage and the extended wavelength range (3000-24800 angstrom), we obtained an unprecedentedly rich spectral sequence among the hypernovae, making SN 2010bh one of the best studied representatives of this SN class. We find that SN 2010bh has a more rapid rise to maximum brightness (8.0 +/- 1.0 rest-frame days) and a fainter absolute peak luminosity (L-bol approximate to 3 x 10(42) erg s(-1)) than previously observed SN events associated with GRBs. Our estimate of the ejected Ni-56 mass is 0.12 +/- 0.02 M-circle dot. From the broad spectral features, we measure expansion velocities up to 47,000 km s(-1), higher than those of SNe 1998bw (GRB 980425) and 2006aj (GRB 060218). Helium absorption lines He I lambda 5876 and He I 1.083 mu m, blueshifted by similar to 20,000-30,000 km s(-1) and similar to 28,000-38,000 km s(-1), respectively, may be present in the optical spectra. However, the lack of coverage of the He I 2.058 mu m line prevents us from confirming such identifications. The nebular spectrum, taken at similar to 186 days after the explosion, shows a broad but faint [O I] emission at 6340 angstrom. The light curve shape and photospheric expansion velocities of SN 2010bh suggest that we witnessed a highly energetic explosion with a small ejected mass (E-k approximate to 10(52) erg and M-ej approximate to 3 M-circle dot). The observed properties of SN 2010bh further extend the heterogeneity of the class of GRB SNe.
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| 2. |
- Christensen, Lise, et al.
(författare)
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Gravitationally lensed galaxies at 2 < z < 3.5 : direct abundance measurements of Ly alpha emitters
- 2012
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 427:3, s. 1973-1982
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Tidskriftsartikel (refereegranskat)abstract
- Strong gravitational lensing magnifies the flux from distant galaxies, allowing us to detect emission lines that would otherwise fall below the detection threshold for medium-resolution spectroscopy. Here we present the detection of temperature-sensitive oxygen emission lines from three galaxies at 2 ? z ? 3.5, which enables us to directly determine the oxygen abundances and thereby double the number of galaxies at z > 2 for which this has been possible. The three galaxies have similar to 10?per?cent solar oxygen abundances in agreement with strong emission-line diagnostics. Carbon and nitrogen ratios relative to oxygen are subsolar as expected for young metal-poor galaxies. Two of the galaxies are Lyman a (Lya) emitters with rest-frame equivalent widths of 20 and 40 angstrom, respectively, and their high magnification factors allow us for the first time to gain insight into the physical characteristics of high-redshift Lya emitters. Using constraints from the physical properties of the galaxies, we accurately reproduce their line profiles with radiative transfer models. The models show a relatively small outflow in agreement with the observed small velocity offsets between nebular emission and interstellar absorption lines.
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| 3. |
- Christensen, Lise, et al.
(författare)
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The low-mass end of the fundamental relation for gravitationally lensed star-forming galaxies at 1 < z < 6
- 2012
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 427:3, s. 1953-1972
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Forskningsöversikt (refereegranskat)abstract
- We present Very Large Telescope/X-shooter spectra of 13 galaxies in the redshift range 1 ? z ? 6, which are strongly lensed by massive galaxy clusters. Spectroscopic redshifts are measured for nine galaxies, while three sources have redshifts determined from continuum breaks in their spectra. The stellar masses of the galaxies span four orders of magnitude between 107 and 1011?M? and have luminosities at 1500 angstrom rest frame between 0.004 and 9L* after correcting for the magnification. This allows us to probe a variety of galaxy types from young, low-mass starburst galaxies to massive evolved galaxies. The lensed galaxies with stellar masses less than 1010?M? have a large scatter compared to the fundamental relation between stellar mass, star formation rates and oxygen abundances. We provide a modified fit to the fundamental relation for low-mass, low-metallicity galaxies with a weaker dependence of the metallicity on either the star formation rate or stellar mass compared to low-redshift, high-mass and high-metallicity Sloan Digital Sky Survey galaxies.
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| 4. |
- Stark, Daniel P., et al.
(författare)
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Ultraviolet emission lines in young low-mass galaxies at z similar or equal to 2 : physical properties and implications for studies at z > 7
- 2014
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 445:3, s. 3200-3220
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Tidskriftsartikel (refereegranskat)abstract
- We present deep spectroscopy of 17 very low mass (M* similar or equal to 2.0 x 10(6)-1.4 x 10(9) M-circle dot) and low luminosity (M-UV similar or equal to -13.7 to -19.9) gravitationally lensed galaxies in the redshift range z similar or equal to 1.5-3.0. Deep rest-frame ultraviolet spectra reveal large equivalent width emission from numerous emission lines (N IV], O III], C IV, Si III], C III]) which are rarely seen in individual spectra of more massive star-forming galaxies. C III] is detected in 16 of 17 low-mass star-forming systems with rest-frame equivalent widths as large as 13.5 angstrom. Nebular C (IV) emission is present in the most extreme C III] emitters, requiring an ionizing source capable of producing a substantial component of photons with energies in excess of 47.9 eV. Photoionization models support a picture whereby the large equivalent widths are driven by the increased electron temperature and enhanced ionizing output arising from metal-poor gas and stars (0.04-0.13 Z(circle dot)), young stellar populations (6-50 Myr), and large ionization parameters (log U = -2.16 to -1.84). The young ages implied by the emission lines and continuum spectral energy distributions (SEDs) indicate that the extreme line emitters in our sample are in the midst of a significant upturn in their star formation activity. The low stellar masses, blue UV colours, and large specific star formation rates of our sample are similar to those of typical z greater than or similar to 6 galaxies. Given the strong attenuation of Ly alpha in z greater than or similar to 6 galaxies, we suggest that C III] is likely to provide our best probe of early star-forming galaxies with ground-based spectrographs and one off the most efficient means of confirming z greater than or similar to 10 galaxies with the James Webb Space Telescope.
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