The nature of the optical-radio correlations for powerful radio galaxies is investigated using spectroscopic observations of a complete sample of southern 2-Jy radio sources. In line with previous ...work, we find that significant correlations exist between the luminosities of the O IIIλ 5007, O IIλ 3727 and Hβ emission lines and the radio luminosity. However, our observations are not easily reconciled with the idea that these correlations are caused by the increase in the power of the photoionizing quasar as the jet power increases, with average ISM properties not changing appreciably with redshift or radio power: not only do we find that the scatter in the LO iii versus Lradio correlation is significantly larger than in LO ii versus Lradio and LHβ versus Lradio correlations, but the ionization state deduced from the emission lines does not increase with radio power as predicted by the simple, constant ISM, photoionization model. We conclude that (a) there exists a considerable range in the quasar ionizing luminosity at a given redshift, and (b) the mean density of the emission-line clouds is larger in the high-redshift/high-power radio sources. The latter density enhancement may be either a consequence of the increased importance of jet-cloud interactions or, alternatively, the result of a higher pressure in the confining hot ISM, in the high-redshift objects. Apart from the general scatter in the correlations, we identify a distinct group of objects with O IIIλ 5007 luminosities which are more than an order of magnitude lower than in the general population radio galaxies at similar redshift. These weak-line radio galaxies (WLRGs) are likely to be sources in which the central ionizing quasars are particularly feeble. Deep spectra show that many of the sources in our sample are broad-line radio galaxies (BLRGs). The fact that the BLRGs are observed out to the redshift limit of the survey, overlapping in redshift with the quasars, argues against the idea that BLRGs are simply the low-radio-power counterparts of high-power, high-redshift quasars. Either there exists a considerable range in the intrinsic luminosities of the broad-line AGN for a given redshift or radio power, or the BLRGs represent partially obscured quasars. The degree of scatter present in the LOiii versus Lradio correlation supports the former possibility.
ABSTRACT Due to stellar rotation, the observed radial velocity of a star varies during the transit of a planet across its surface, a phenomenon known as the Rossiter-McLaughlin (RM) effect. The ...amplitude of the RM effect is related to the radius of the planet which, because of differential absorption in the planetary atmosphere, depends on wavelength. Therefore, the wavelength-dependent RM effect can be used to probe the planetary atmosphere. We measure for the first time the RM effect of the Earth transiting the Sun using a lunar eclipse observed with the ESO High Accuracy Radial velocity Planet Searcher spectrograph. We analyze the observed RM effect at different wavelengths to obtain the transmission spectrum of the Earth's atmosphere after the correction of the solar limb-darkening and the convective blueshift. The ozone Chappuis band absorption as well as the Rayleigh scattering features are clearly detectable with this technique. Our observation demonstrates that the RM effect can be an effective technique for exoplanet atmosphere characterization. Its particular asset is that photometric reference stars are not required, circumventing the principal challenge for transmission spectroscopy studies of exoplanet atmospheres using large ground-based telescopes.
Due to stellar rotation, the observed radial velocity of a star varies during the transit of a planet across its surface, a phenomenon known as the Rossiter–McLaughlin (RM) effect. The amplitude of ...the RM effect is related to the radius of the planet which, because of differential absorption in the planetary atmosphere, depends on wavelength. Therefore, the wavelength-dependent RM effect can be used to probe the planetary atmosphere. We measure for the first time the RM effect of the Earth transiting the Sun using a lunar eclipse observed with the ESO High Accuracy Radial velocity Planet Searcher spectrograph. We analyze the observed RM effect at different wavelengths to obtain the transmission spectrum of the Earth’s atmosphere after the correction of the solar limb-darkening and the convective blueshift. The ozone Chappuis band absorption as well as the Rayleigh scattering features are clearly detectable with this technique. Our observation demonstrates that the RM effect can be an effective technique for exoplanet atmosphere characterization. Its particular asset is that photometric reference stars are not required, circumventing the principal challenge for transmission spectroscopy studies of exoplanet atmospheres using large ground-based telescopes.
Aims.The purpose of this study is to explore the relationship between galaxy stellar masses, based on multiwavelength photometry spectral template fitting and dynamical masses based on published ...velocity dispersion measurements, for a sample of 48 early-type galaxies at $z \sim 1$ with HST/ACS morphological information. Methods.We determine photometric-stellar masses and perform a quantitative morphological analysis of cluster and field galaxies at redshift $0.6< z < 1.2$, using ground- and space-based multiwavelength data available on the GOODS-S field and on the field around the X-ray luminous cluster RDCS1252.9-2927 at $z=1.24$. We use multi-band photometry over 0.4–8 μm from HST/ACS, VLT/ISAAC and Spitzer/IRAC to estimate photometric-stellar masses using Composite Stellar Population (CSP) templates computed with PEGASE.2 (Fioc & Rocca-Volmerange 1997) models. We compare stellar masses with those obtained using CSPs built with Bruzual & Charlot (2003, MNRAS, 344, 1000; BC03) and Maraston (2005, MNRAS, 362, 799; M05) models. We then compare photometric-stellar mass and dynamical mass estimates as a function of morphological parameters obtained from HST/ACS imaging. Results.Based on our sample, which spans the mass range $\log M_{\rm phot} \simeq 10,11.5$, we find that 1) PEGASE.2, BC03, M05 yield consistent photometric-stellar masses for early-type galaxies at $z \sim 1$ with a small scatter (0.15 dex rms); 2) adopting a Kroupa IMF, photometric-stellar masses match dynamical mass estimates for early-type galaxies with an average offset of 0.27 dex; 3) assuming a constant IMF, increasing dark matter fraction with the increasing galaxy mass can explain the observed trend; 4) we observe that early-type galaxies with significant disk components (Sa/Sab) or with signs of dynamical interaction tend to have the largest deviation from a one-to-one $M_{\rm dyn} \,{\rm vs}.\, M_{\rm phot}$ relation
PKSB2152-699, which has radio power characteristic of sources that dominate radio feedback, is exceptional in showing a wide range of features associated with radio-galaxy/gas interactions. We ...present new deep radio (Australia Telescope Compact Array), X-ray (Chandra) and ground-based optical observations, and test the energetics of the feedback model. We report the first high-resolution observations of the radio jet, finding that the inner jet extends 8.5kpc (10° viewing angle) in the direction of an optical emission-line high-ionization cloud (HIC) before taking a zigzag path to a position offset from the HIC. Jet synchrotron radiation to X-ray energies is seen. The HIC is associated with cool, kT 0.3keV, X-ray gas of anomalously low metallicity. On larger scales, the radio galaxy displays all three X-ray features that together confirm supersonic expansion of the lobes into the external medium: gas cavities, inverse Compton emission showing excess internal lobe pressure, and high-contrast arms of temperature above the kT 1keV ambient medium. The well-formed southern lobe on the counterjet side is expanding with a Mach number between 2.2 and 3. The lobe energy appears to be more gently dissipated in the north. We estimate a cavity power 3 × 1043ergs-1, which falls well below previously reported correlations with radio power. The total inferred time-averaged jet power, 4 × 1044ergs-1, is dominated by the kinetic and thermal energy of shocked gas, and if used instead would bring the source into better agreement with the correlations. The southern hotspot is the more complex, with a spiral polarization structure. Its bright peak emits synchrotron X-rays. The fainter northern hotspot is particularly interesting, with X-rays offset in the direction of the incoming jet by 1arcsec relative to the radio peak. Here modest (delta 6) relativistic beaming and a steep radio spectrum cause the jet to be X-ray bright through inverse Compton scattering before it decelerates. With such beaming, a modest proton content or small departure from minimum energy in the jet will align estimates of the instantaneous and time-averaged jet power. The hotspots suggest acceleration of electrons to a maximum energy 1013eV in the jet termination shocks. PUBLICATION ABSTRACT
Lyman-break galaxies are now regularly found in the high redshift Universe by searching for the break in the galaxy spectrum caused by the Lyman-limit redshifted into the optical or even near-IR. ...At lower redshift, this break is covered by the GALEX UV channels and small samples of z ~ 1 LBGs have been presented in the literature. Here we give results from fitting the spectral energy distributions of a small sub-set of low redshift LBGs and demonstrate the advantage of including photometric points derived from HST ACS slitless grism observations. The results show these galaxies to have very young, star forming populations, while still being massive and dusty. LBGs at low and high redshift show remarkable similarities in their properties, indicating that the LBG selection method picks similar galaxies throughout the Universe.
The nature of the optical–radio correlations for powerful radio galaxies is investigated using spectroscopic observations of a complete sample of southern 2‐Jy radio sources. In line with previous ...work, we find that significant correlations exist between the luminosities of the O IIIλ 5007, O IIλ 3727 and Hβ emission lines and the radio luminosity. However, our observations are not easily reconciled with the idea that these correlations are caused by the increase in the power of the photoionizing quasar as the jet power increases, with average ISM properties not changing appreciably with redshift or radio power: not only do we find that the scatter in the LO iii versus Lradio correlation is significantly larger than in LO ii versus Lradio and LHβ versus Lradio correlations, but the ionization state deduced from the emission lines does not increase with radio power as predicted by the simple, constant ISM, photoionization model. We conclude that (a) there exists a considerable range in the quasar ionizing luminosity at a given redshift, and (b) the mean density of the emission‐line clouds is larger in the high‐redshift/high‐power radio sources. The latter density enhancement may be either a consequence of the increased importance of jet–cloud interactions or, alternatively, the result of a higher pressure in the confining hot ISM, in the high‐redshift objects. Apart from the general scatter in the correlations, we identify a distinct group of objects with O IIIλ 5007 luminosities which are more than an order of magnitude lower than in the general population radio galaxies at similar redshift. These weak‐line radio galaxies (WLRGs) are likely to be sources in which the central ionizing quasars are particularly feeble. Deep spectra show that many of the sources in our sample are broad‐line radio galaxies (BLRGs). The fact that the BLRGs are observed out to the redshift limit of the survey, overlapping in redshift with the quasars, argues against the idea that BLRGs are simply the low‐radio‐power counterparts of high‐power, high‐redshift quasars. Either there exists a considerable range in the intrinsic luminosities of the broad‐line AGN for a given redshift or radio power, or the BLRGs represent partially obscured quasars. The degree of scatter present in the LOiii versus Lradio correlation supports the former possibility.
The great observatories origins deep survey Vanzella, E.; Cristiani, S.; Dickinson, M. ...
Astronomy and astrophysics (Berlin),
08/2006, Letnik:
454, Številka:
2
Journal Article
A programme has been started to investigate photon properties that are not currently exploited in astronomical instruments, namely second- and higher-order coherence functions encoded in their ...arrival time, and the orbital angular momentum. This paper expounds the first results achieved in the study of a novel astronomical photometer capable of pushing time tagging towards the picosecond region. This conceptual device has been developed as a possible focal plane instrument for the future OverWhelmingly Large Telescope (OWL) of the European Southern Observatory. This instrument has been named QuantEYE, that is, the Quantum Eye of OWL.
We present optical spectra for a complete sample of radio galaxies and quasars comprising all sources from the Wall & Peacock 2.7-GHz sample with redshifts z < 0.7 and declinations δ < + 10°; this ...sample is complete down to a flux density of 2 Jy. Although not all of the 2-Jy sources have spectroscopic redshifts, we argue that most of the unidentified objects are at high redshifts and that our z < 0.7 sample is largely complete. The optical data will be analysed in a future paper.
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