We present dynamical and structural scaling relations of quiescent galaxies at z = 2, including the dynamical mass-size relation and the first constraints on the fundamental plane (FP). The backbone of the analysis is a new, very deep VLT/X-shooter spectrum of a massive, compact, quiescent galaxy at z = 2.0389. We detect the continuum between 3700-22000Å and several strong absorption features (Balmer series, Ca H+K, G-band), from which we derive a stellar velocity dispersion of 318 ± 53 km s −1 . We perform detailed modeling of the continuum emission and line indices and derive strong simultaneous constraints on the age, metallicity, and stellar mass. The galaxy is a dusty (A V = 0.77 +0.36 −0.32 ) solar metallicity (log(Z/Z ) = 0.02 +0.20 −0.41 ) post starburst galaxy, with a mean luminosity weighted log(age/yr) of 8.9 ± 0.1. The galaxy formed the majority of its stars at z > 3 and currently has little or no ongoing star formation. We compile a sample of three other z ∼ 2 quiescent galaxies with measured velocity dispersions, two of which are also post starburst like. Their dynamical masssize relation is offset significantly less than the stellar mass-size relation from the local early type relations, which we attribute to a lower central dark matter fraction. Recent cosmological merger simulations qualitatively agree with the data, but can not fully account for the evolution in the dark matter fraction. The z ∼ 2 FP requires additional evolution beyond passive stellar aging, to be in agreement with the local FP. The structural evolution predicted by the cosmological simulations is insufficient, suggesting that additional, possibly non-homologous structural evolution is needed.

Aims. We have studied the afterglow of the gamma-ray burst (GRB) of February 18, 2006. This is a nearby long GRB, with a very low peak energy, and is therefore classified as an X-ray Flash (XRF). XRF 060218 is clearly associated with a supernova -dubbed SN 2006aj. Methods. We present early spectra for SN 2006aj as well as optical lightcurves reaching out to 50 days past explosion. Results. Our optical lightcurves define the rise times, the lightcurve shapes and the absolute magnitudes in the U, V and R bands, and we compare these data with data for other relevant supernovae. SN 2006aj evolved quite fast, somewhat similarly to SN 2002ap, but not as fast as SN 1994I. Our spectra show the evolution of the supernova over the peak, when the U-band portion of the spectrum rapidly fades due to extensive line blanketing. We compare to similar spectra of very energetic type Ic supernovae. Our first spectra are earlier than spectra for any other GRB-SN. The spectrum taken 12 days after burst in the rest frame is similar to somewhat later spectra of both SN 1998bw and SN 2003dh, implying a rapid early evolution. This is consistent with the fast lightcurve. From the narrow emission lines from the host galaxy we derive a redshift of z = 0.0331 ± 0.0007. This makes XRF 060218 the second closest gamma-ray burst detected. The flux of these emission lines indicate a high-excitation state, and a modest metallicity and star formation rate of the host galaxy.

The results of analysis of HST I−band imaging of a sample of 41 radio galaxies spanning three orders of magnitude in radio luminosity at redshift z ≃ 0.5 are presented. These results represent the first stage in a coordinated programme to study the connection between radio luminosity and host-galaxy properties, black-hole masses and cluster environments in radio galaxies spanning a wide range in radio luminosity over a restricted range in redshift. The full sample is comprised of objects drawn from four complete, low-frequency selected radio samples with progressively fainter flux-density limits (3CRR, 6CE, 7CRS and the new TexOx-1000 sample). Modelling of the HST imaging data shows that the host galaxies have surface-brightness distributions consistent with those expected for classic ellipticals (Sérsic parameter, β ≃ 0.25), with β in the range 0.17 < β < 0.30, and a mean of < β >= 0.23 ± 0.01. The luminosities of the host galaxies are found to be comparable with those of galaxies drawn from the bright end of the local cluster galaxy luminosity function, spanning the range 0.7L ⋆ < L < 10L ⋆ , with a mean of 3.2 ± 0.3L ⋆ , after correcting for the effects of passive evolution. In addition, the radio galaxies are shown to follow a Kormendy (µ e −r e ) relation indistinguishable from that of both powerful low-redshift radio galaxies and local Abell brightest cluster galaxies. Combining our new results with those in the literature it is found that the scalelengths and Kormendy relations of 3C-class radio galaxies do not vary significantly over the redshift range 0.0 < z < 0.8, providing no evidence for dynamical evolution of this class of host galaxy within this redshift interval. Converting the host-galaxy luminosities into black-hole mass estimates, using the local M bh − M bulge correlation, predicts that the radio galaxies harbour central black holes with masses in the range 10 8.1 M ⊙ < M bh < 10 9.5 M ⊙ , with a geometric mean of < M bh >= 10 8.87±0.04 M ⊙ . Finally, a significant (≃ 3σ) correlation is found between black-hole mass and 151-MHz radio luminosity for those objects in the sample with either high-excitation nuclear spectra (HEG) or classical double (CD) radio structures.

A B S T R A C TWe have observed the galaxy environments around a sample of 21 radio-loud, steepspectrum quasars at 0X5 # z # 0X82Y spanning several orders of magnitude in radio luminosity. The observations also include background control fields used to obtain the excess number of galaxies in each quasar field. The galaxy excess was quantified using the spatial galaxy±quasar correlation amplitude, B gq , and an Abell-type measurement, N 0.5 . A few quasars are found in relatively rich clusters, but on average, they seem to prefer galaxy groups or clusters of approximately Abell class 0. We have combined our sample with literature samples extending down to z < 0X2 and covering the same range in radio luminosity. By using the Spearman statistic to disentangle redshift and luminosity dependences, we detect a weak, but significant, positive correlation between the richness of the quasar environment and the radio luminosity of the quasar. However, we do not find any epoch dependence in B gq , as has previously been reported for radio quasars and galaxies. We discuss the radio luminosity±cluster richness link and possible explanations for the weak correlation that is seen.

In order to investigate the dependence of quasar variability on fundamental physical parameters like black hole mass, we have matched quasars from the QUEST1 Variability Survey with broad-lined objects from the Sloan Digital Sky Survey. The matched sample contains approximately 100 quasars, and the Sloan spectra are used to estimate black hole masses and bolometric luminosities. Variability amplitudes are measured from the QUEST1 light curves. We find that black hole mass correlates with several measures of the variability amplitude at the 99% significance level or better. The correlation does not appear to be caused by obvious selection effects inherent to flux-limited quasar samples, host galaxy contamination or other well-known correlations between quasar variability and luminosity/redshift. We evaluate variability as a function of rest-frame time lag using structure functions, and find further support for the variability--black hole mass correlation. The correlation is strongest for time lags of the order a few months up to the QUEST1 maximum temporal resolution of approximately 2 years, and may provide important clues for understanding the long-standing problem of the origin of quasar optical variability. We discuss whether our result is a manifestation of a relation between characteristic variability timescale and black hole mass, where the variability timescale is typical for accretion disk thermal timescales, but find little support for this. Our favoured explanation is that more massive black holes have larger variability amplitudes, and we highlight the need for larger samples with more complete temporal sampling to test the robustness of this result.Comment: 12 pages, 6 figures. Accepted for publication in MNRA