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Register a new userThe Water Vapor Spectrum of APM 08279+5255: X-Ray Heating and Infrared Pumping over Hundreds of Parsecs
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Charles M. Bradford
Publication date
2011
fields
Physics
and research's language is
English
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We present the rest-frame 200--320 mm spectrum of the z=3.91 quasar apm, obtained with Z-Spec at the Caltech Submillimeter Observatory. In addition to the jeight to jthirteen CO rotational transitions which dominate the CO cooling, we find six transitions of water originating at energy levels ranging up to 643 K. Most are first detections at high redshift, and we have confirmed one transition with CARMA. The CO cooling is well-described by our XDR model, assuming L$_{rm 1-100,keV}sim1times10^{46}rm,erg,s^{-1}$, and that the gas is distributed over a 550-pc sizescale, per the now-favored $mu$=4 lensing model. The total observed cooling in water corresponds to 6.5$times10^{9}$ ls, comparable to that of CO. We compare the water spectrum with that of Mrk 231, finding that the intensity ratios among the high-lying lines are similar, but with a total luminosity scaled up by a factor of $sim$50. Using this scaling, we estimate an average water abundance relative to hh of 1.4$times10^{-7}$, a good match to the prediction of the chemical network in the XDR model. As with Mrk 231, the high-lying water transitions are excited radiatively via absorption in the rest-frame far-infrared, and we show that the powerful dust continuum in apm is more than sufficient to pump this massive reservoir of warm water vapor.
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We report a detection of the excited 220-211 rotational transition of para-H2O in APM 08279+5255 using the IRAM Plateau de Bure interferometer. At z = 3.91, this is the highest-redshift detection of interstellar water to date. From LVG modeling, we conclude that this transition is predominantly radiatively pumped and on its own does not provide a good estimate of the water abundance. However, additional water transitions are predicted to be detectable in this source, which would lead to an improved excitation model. We also present a sensitive upper limit for the HF J = 1 - 0 absorption toward APM 08279+5255. While the face-on geometry of this source is not favorable for absorption studies, the lack of HF absorption is still puzzling and may be indicative of a lower fluorine abundance at z = 3.91 compared with the Galactic ISM.
The Infrared Spectrograph (IRS) onboard the Spitzer Space Telescope (SST) has been used to obtain low and moderate resolution spectra of the dust and gas-rich quasar APM08279+5255 (z=3.91). Broad Paschen $alpha$ and $beta$ recombination lines of hydrogen were detected at wavelengths of 9.235 and 6.315microns, as well as a strong, red continuum that is a smooth power law over the observed (rest frame) wavelength range 5.3-35microns (1.08 - 7.1microns). The observed P$alpha$/P$beta$ line flux ratio of 1.05$pm$0.2 is far from the case B value of ~2 and simple models of high density, high optical depth ionized gas regions (~1.8). This deviation is opposite in sense to the expected effect of reddening. No evidence is found in the spectrum for either the 3.3micron or 6.2micron emission features usually attributed to aromatic hydrocarbons in gas rich galaxies in the local Universe. This is consistent with the high luminosity AGN nature of APM08279+5255.
We present a detection of [CI] line emission in the lensed quasar APM 08279+5255 at z=3.91 using the IRAM Plateau de Bure interferometer. The [CI] line velocity and width are similar to the values of previously detected high-J CO and HCN lines in this source, suggesting that the emission from all of these species arises from the same region. The apparent luminosity of the [CI] line is L(CI) = (3.1 +/- 0.4)x10^10 K km/s pc^2, which implies a neutral carbon mass, M(CI) = (4.4+/-0.6)/m x10^7 M_sun, where m is the lensing magnification factor. The [CI] line luminosity is consistent with the large molecular gas mass inferred from the nuclear CO line luminosity ~10^11 /m M_sun. We also present an upper limit on the H2O line luminosity in APM 08279+5255 of, L(H2O) < 1.8x10^10 K km/s pc^2 (3-sigma).
Broad Absorption Lines indicate gas outflows with velocities from thousands km/s to about 0.2 the speed of light, which may be present in all quasars and may play a major role in the evolution of the host galaxy. The variability of absorption patterns can provide informations on changes of the density and velocity distributions of the absorbing gas and its ionization status. We collected 23 photometrical and spectro-photometrical observations at the 1.82m Telescope of the Asiago Observatory since 2003, plus other 5 spectra from the literature. We analysed the evolution in time of the equivalent width of the broad absorption feature and two narrow absorption systems, the correlation among them and with the R band magnitude. We performed a structure function analysis of the equivalent width variations. We present an unprecedented monitoring of a broad absorption line quasar based on 28 epochs in 14 years. The shape of broad absorption feature shows a relative stability, while its equivalent width slowly declines until it sharply increases during 2011. In the same time the R magnitude stays almost constant until it sharply increases during 2011. The equivalent width of the narrow absorption redwards of the systemic redshift only shows a decline. The broad absorption behaviour suggests changes of the ionisation status as the main cause of variability. We show for the first time a correlation of this variability with the R band flux. The different behaviour of the narrow absorption system might be due to recombination time delay. The structure function of the absorption variability has a slope comparable with typical optical variability of quasars. This is consistent with variations of the 200 A ionising flux originating in the inner part of the accretion disk.
We present Keck high-resolution near-IR (2.2 microns; FWHM~0.15) and mid-IR (12.5 microns; FWHM~0.4) images of APM08279+5255, a z=3.91 IR-luminous BALQSO with a prodigious apparent bolometric luminosity of 5x10^{15} Lsun, the largest known in the universe. The K-band image shows that this system consists of three components, all of which are likely to be the gravitationally lensed images of the same background object, and the 12.5 micron image shows a morphology consistent with such an image configuration. Our lens model suggests that the magnification factor is ~100 from the restframe UV to mid-IR, where most of the luminosity is released. The intrinsic bolometric luminosity and IR luminosity of APM08279+5255 are estimated to be 5x10^{13} Lsun and 1x10^{13} Lsun, respectively. This indicates that APM 08279+5255 is intriniscally luminous, but it is not the most luminous object known. As for its dust contents, little can be determined with the currently available data due to the uncertainties associated with the dust emissivity and the possible effects of differential magnification. We also suggest that the lensing galaxy is likely to be a massive galaxy at z~3.
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