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J. P. U. Fynbo,
C. Ledoux,
P. Noterdaeme,
L. Christensen,
P. Møller,
A. K. Durgapal,
P. Goldoni,
L. Kaper,
J.-K. Krogager,
P. Laursen,
J. R. Maund,
B. Milvang-Jensen,
K. Okoshi,
P. K. Rasmussen,
T. J. Thorsen, S. Toft,
T. Zafar
[show abstract]
[hide abstract]
ABSTRACT: This is the second paper of a series reporting on the results from a survey conducted with the ESO VLT/X-shooter spectrograph. We target high-metallicity damped Lyman α absorbers (DLAs) with the aim of investigating the relation between galaxies detected in emission and those detected in absorption. Here, we report on the discovery of the galaxy counterpart of the zabs= 2.58 DLA on the line-of-sight to the z= 3.07 quasar SDSS J 091826.16+163609.0 (hereafter Q 0918+1636). The galaxy counterpart of the DLA is detected in the [O iii]λ5007 and [O ii]λλ3726, 3729 emission lines redshifted into the NIR at an impact parameter of 2.0 arcsec (16 kpc at z= 2.58). Lyα emission is not detected down to a 3σ detection limit of 5 × 10−18 erg s−1 cm−2, which, compared to the strength of the oxygen lines, implies that Lyα emission from this galaxy is suppressed by more than an order of magnitude. The DLA has one of the highest metallicities measured so far at comparable redshifts. We find evidence for substantial depletion of refractory elements on to dust grains. Fitting the main metal line component of the DLA, which is located at zabs= 2.5832, we measure the metal abundances from Zn ii, S ii, Si ii, Cr ii, Mn ii, Fe ii and Ni ii to be −0.12 ± 0.05, −0.26 ± 0.05, −0.46 ± 0.05, −0.88 ± 0.05, −0.92 ± 0.05, −1.03 ± 0.05 and −0.78 ± 0.05, respectively. In addition, we detect absorption in the Lyman and Werner bands of molecular hydrogen (H2), which represents the first detection of H2 molecules with X-shooter. The background quasar Q 0918+1636 is amongst the reddest QSOs at redshifts 3.02 < z < 3.12 from the SDSS catalogue. Its UV to NIR spectrum is well fitted by a composite QSO spectrum reddened by SMC-/LMC-like extinction curves at zabs= 2.58 with a significant amount of extinction given by AV≈ 0.2 mag. This supports previous claims that there may be more metal-rich DLAs missing from current samples due to dust reddening of the background QSOs. The fact that there is evidence for dust both in the central emitting regions of the galaxy (as evidenced by the lack of Lyα emission) and at an impact parameter of 16 kpc (as probed by the DLA) suggests that dust is widespread in this system.
Monthly Notices of the Royal Astronomical Society 05/2011; 413(4):2481 - 2488. · 4.90 Impact Factor
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J. P. U. Fynbo,
C. Ledoux,
P. Noterdaeme,
L. Christensen,
P. Moller,
A. K. Durgapal,
P. Goldoni,
L. Kaper,
J. -K. Krogager,
P. Laursen,
J. R. Maund,
B. Milvang-Jensen,
K. Okoshi,
P. K. Rasmussen,
T. J. Thorsen, S. Toft,
T. Zafar
[show abstract]
[hide abstract]
ABSTRACT: [Abridged]. Here, we report on the discovery of the galaxy counterpart of the
z_abs=2.58 DLA on the line-of-sight to the z=3.07 quasar SDSS
J091826.16+163609.0. The galaxy counterpart of the DLA is detected in the OIII
5007 and OII 3726,3729 emission lines redshifted into the NIR at an impact
parameter of 16 kpc. Ly-alpha emission is not detected. The upper limit implies
that Ly-alpha emission from this galaxy is suppressed by more than an order of
magnitude. The DLA is amongst the most metal-rich DLAs studied so far at
comparable redshifts. We find evidence for substantial depletion of refractory
elements onto dust grains. Fitting the main metal line component of the DLA,
which is located at z_abs=2.5832 and accounts for at least 85% of the total
column density of low-ionisation species, we measure metal abundances from
ZnII, SII, SiII, CrII, MnII, FeII and NiII of -0.12, -0.26, -0.46, -0.88,
-0.92, -1.03 and -0.78, respectively. In addition, we detect absorption in the
Lyman and Werner bands of hydrogen, which represents the first detection of H_2
molecules with X-shooter. The background quasar Q0918+1636 is amongst the
reddest QSOs at redshifts 3.02<z<3.12 from the SDSS catalogue. Its UV to NIR
spectrum is well fitted by a composite QSO spectrum reddened by SMC/LMC-like
extinction curves at z_abs=2.58 with a significant amount of extinction given
by A_V = 0.2 mag. This supports previous claims that there may be more
metal-rich DLAs missing from current samples due to dust reddening of the
background QSOs. The fact that there is evidence for dust both in the central
emitting regions of the galaxy (as evidenced by the lack of Ly-alpha emission)
and at an impact parameter of 16 kpc (as probed by the DLA) suggests that dust
is widespread in this system.
11/2010;
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J. P. U. Fynbo,
P. Laursen,
C. Ledoux,
P. Møller,
A. K. Durgapal,
P. Goldoni,
B. Gullberg,
L. Kaper,
J. Maund,
P. Noterdaeme,
G. Östlin,
M. L. Strandet, S. Toft,
P. M. Vreeswijk,
T. Zafar
[show abstract]
[hide abstract]
ABSTRACT: We have initiated a survey using the newly commissioned X-shooter spectrograph to target candidate relatively metal-rich damped Lyα absorbers (DLAs). Our rationale is that high-metallicity DLAs due to the luminosity–metallicity relation likely will have the most luminous galaxy counterparts. In addition, the spectral coverage of X-shooter allows us to search for not only Lyα emission, but also rest-frame optical emission lines. We have chosen DLAs where the strongest rest-frame optical lines ([O ii], [O iii], Hβ and Hα) fall in the near-infrared atmospheric transmission bands. In this first paper resulting from the survey, we report on the discovery of the galaxy counterpart of the zabs= 2.354 DLA towards the z= 2.926 quasar Q 2222−0946. This DLA is amongst the most metal-rich z > 2 DLAs studied so far at comparable redshifts and there is evidence for substantial depletion of refractory elements on to dust grains. We measure metallicities from Zn ii, Si ii, Ni ii, Mn ii and Fe ii of −0.46 ± 0.07, − 0.51 ± 0.06, − 0.85 ± 0.06, − 1.23 ± 0.06 and −0.99 ± 0.06, respectively. The galaxy is detected in the Lyα, [O iii]λλ4959, 5007 and Hα emission lines at an impact parameter of about 0.8 arcsec (6 kpc at zabs= 2.354). Based on the Hα line, we infer a star formation rate of 10 M⊙ yr−1, which is a lower limit due to the possibility of slit loss. Compared to the recently determined Hα luminosity function for z= 2.2 galaxies, the DLA-galaxy counterpart has a luminosity of L∼ 0.1L*Hα. The emission-line ratios are 4.0 (Lyα/Hα) and 1.2 ([O iii]/Hα). In particular, the Lyα line shows clear evidence for resonant scattering effects, namely an asymmetric, redshifted (relative to the systemic redshift) component and a much weaker blueshifted component. The fact that the blueshifted component is relatively weak indicates the presence of a galactic wind.The properties of the galaxy counterpart of this DLA are consistent with the prediction that metal-rich DLAs are associated with the most luminous of the DLA-galaxy counterparts.
Monthly Notices of the Royal Astronomical Society 11/2010; 408(4):2128 - 2136. · 4.90 Impact Factor
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J. P. U. Fynbo,
P. Laursen,
C. Ledoux,
A. K. Durgapal,
P. Møller,
P. Goldoni,
B. Gullberg,
L. Kaper,
J. Maund,
P. Noterdaeme,
G. Ostlin,
M. L. Strandet, S. Toft,
P. M. Vreeswijk,
T. Zafar
[show abstract]
[hide abstract]
ABSTRACT: We have initiated a survey using the newly commissioned X-shooter
spectrograph to target candidate relatively metal-rich damped Lyman-alpha
absorbers (DLAs). The spectral coverage of X-shooter allows us to search for
not only Lyman-alpha emission, but also rest-frame optical emission lines. We
have chosen DLAs where the strongest rest-frame optical lines ([OII], [OIII],
Hbeta and Halpha) fall in the NIR atmospheric transmission bands. In this first
paper resulting from the survey, we report on the discovery of the galaxy
counterpart of the z_abs = 2.354 DLA towards the z=2.926 quasar Q2222$-0946.
This DLA is amongst the most metal-rich z>2 DLAs studied so far at comparable
redshifts and there is evidence for substantial depletion of refractory
elements onto dust grains. We measure metallicities from ZnII, SiII, NiII, MnII
and FeII of -0.46+/-0.07, -0.51+/-0.06, -0.85+/-0.06, -1.23+/-0.06, and
-0.99+/-0.06, respectively. The galaxy is detected in the Lyman-alpha, [OIII]
lambda4959,5007 Halpha emission lines at an impact parameter of about 0.8
arcsec (6 kpc at z_abs = 2.354). We infer a star-formation rate of 10 M_sun
yr^-1, which is a lower limit due to the possibility of slit-loss. Compared to
the recently determined Halpha luminosity function for z=2.2 galaxies the
DLA-galaxy counterpart has a luminosity of L~0.1L^*_Halpha. The emission-line
ratios are 4.0 (Lyalpha/Halpha) and 1.2 ([OIII]/Halpha). The Lyalpha line shows
clear evidence for resonant scattering effects, namely an asymmetric,
redshifted (relative to the systemic redshift) component and a much weaker
blueshifted component. The fact that the blueshifted component is relatively
weak indicates the presence of a galactic wind. The properties of the galaxy
counterpart of this DLA is consistent with the prediction that metal-rich DLAs
are associated with the most luminous of the DLA-galaxy counterparts.
02/2010;
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J. Hjorth,
P. Møller,
J. Gorosabel,
J. P. U. Fynbo, S. Toft,
A. O. Jaunsen,
A. A. Kaas,
T. Pursimo,
K. Torii,
T. Kato, [......],
N. Masetti,
E. Palazzi,
H. Pedersen,
E. Pian,
J. Rhoads,
E. Rol,
N. R. Tanvir,
P. M. Vreeswijk,
R. A. M. J. Wijers,
and E. P. J. van den Heuvel
[show abstract]
[hide abstract]
ABSTRACT: We present optical and near-infrared observations of the dim afterglow of GRB 020124, obtained between 2 and 68 hr after the gamma-ray burst. The burst occurred in a very faint (R 29.5) damped Lyα absorber (DLA) at a redshift of z = 3.198 ± 0.004. The derived column density of neutral hydrogen is log(N) = 21.7 ± 0.2, and the rest-frame reddening is constrained to be E(B-V) < 0.065, i.e., AV < 0.20 for standard extinction laws with RV ≈ 3. The resulting dust-to-gas ratio is less than 11% of that found in the Milky Way but consistent with the SMC and high-redshift QSO DLAs, indicating a low metallicity and/or a low dust-to-metal ratio in the burst environment. A gray extinction law (large RV), produced through preferential destruction of small dust grains by the gamma-ray burst, could increase the derived AV and dust-to-gas ratio. The dimness of the afterglow is, however, fully accounted for by the high redshift: if GRB 020124 had been at z = 1, it would have been approximately 1.8 mag brighter—in the range of typical bright afterglows.
The Astrophysical Journal 12/2008; 597(2):699. · 6.02 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: We present a survey of the extinction properties of 10 lensing galaxies, in the redshift range z = 0.04-1.01, using multiply lensed quasars imaged with the ESO VLT in the optical and near-infrared. The multiple images act as "standard light sources" shining through different parts of the lensing galaxy, allowing for extinction studies by comparison of pairs of images. We explore the effects of systematics in the extinction curve analysis, including extinction along both lines of sight and microlensing, using theoretical analysis and simulations. In the sample, we see variation in both the amount and type of extinction. Of the 10 systems, seven are consistent with extinction along at least one line of sight. The mean differential extinction for the most extinguished image pair for each lens is (V) = 0.56 ± 0.04, using Galactic extinction law parameterization. The corresponding mean V = 2.8 ± 0.4 is consistent with that of the Milky Way at RV = 3.1, where RV = A(V)/E(B - V). We do not see any strong evidence for evolution of extinction properties with redshift. Of the 10 systems, B1152+199 shows the strongest extinction signal of A(V) = 2.43 ± 0.09 and is consistent with a Galactic extinction law with RV = 2.1 ± 0.1. Given the similar redshift distribution of SN Ia hosts and lensing galaxies, a large space-based study of multiply imaged quasars would be a useful complement to future dark energy SN Ia surveys, providing independent constraints on the statistical extinction properties of galaxies up to z ~ 1.
The Astrophysical Journal Supplement Series 12/2008; 166(2):443. · 13.46 Impact Factor
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A. J. Castro-Tirado,
V. V. Sokolov,
J. Gorosabel,
J. M. Castro Cerón,
J. Greiner,
R. A. M. J. Wijers,
B. L. Jensen,
J. Hjorth, S. Toft,
H. Pedersen, [......],
G. Feulner,
S. Dreizler,
D Hartmann,
H. Boehnhardt,
J. M. Paredes,
J. Martí,
E. Xanthopoulos,
H. E. Kristen,
J. Smoker,
K. Hurley
[show abstract]
[hide abstract]
ABSTRACT: Broad-band optical observations of the extraordinarily bright optical afterglow of the intense gamma-ray burst GRB 991208 started ~2.1 days after the event and continued until 4 Apr. 2000. The flux decay constant of the optical afterglow in the $R$-band is $-$2.30 $\pm$ 0.07 up to ~5 days, which is very likely due to the jet e ffect, and it is followed by a much steeper decay with constant $-$3.2 $\pm$ 0.2, the fastest one ever seen in a GRB optical afterglow. A negative detection in several all-sky films taken simultaneously with the event, that otherwise would have reached naked eye brightness, implies either a previous additional break prior to ~2 days after the occurrence of the GRB (as expected from the jet effect) or a maximum, as observed in GRB 970508. The existence of a se cond break might indicate a steepening in the electron spectrum or the superposition of two events, resembling GRB 000301C. Once the afterglow emission vanished, contribution of a bright underlying supernova was found on the basis of the late-time $R$-band measurements, but the light curve is not sufficiently well sampled to rule out a dust echo explanation. Our redshift determination of $z = 0.706$ indicates that GRB 991208 is at 3.7 Gpc (for $H_{0}= 60$ km s$^{-1}$ Mpc$^{-1}$, $\Omega_{0}= 1$ and $\Lambda_{0}= 0$), implying an isotropic energy release of 1.15$ 10^{53}$ erg which may be relaxed by beaming by a factor $> $10$^{2}$. Precise astrometry indicates that the GRB coincides within 0.2$^{\prime\prime}$ with the host galaxy, thus supporting a massive star origin. The absolute magnitude of the galaxy is $M_{B}$ = $-$18.2, well below the knee of the galaxy luminosity function and we derive a star-forming rate of ($11.5 \pm 7.1$) $M_{\odot}$ yr$^{-1}$, which is much larger than the present-day rate in our Galaxy. The quasi-simultaneous broad-band photometric spectral energy distribution of the afterglow was determined ~3.5 day after the burst (Dec. 12.0) implying a cooling frequency $\nu_{\rm c}$ below the optical band, i.e. supporting a jet model with $p = -$2.30 as the index of the power-law electron distribution.
http://dx.doi.org/10.1051/0004-6361:20010247.
