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Register a new userStructure of the MgII and damped Lyman-alpha systems along the line of sight to APM 08279+5255
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A study of the absorption systems toward the gravitationally lensed quasar APM 08279+5255 is presented. Most of the MgII systems in the redshift range 1.2-2.07, although saturated, show large residuals at the bottom of the lines. The most likely interpretation is that individual clouds within MgII halos do cover only one of the two brightest QSO images. This reveals that MgII halos are made of a collection of clouds of radius smaller than about 1 kpc. Two strong MgII absorbers at z = 1.062 and 1.181 are studied in detail. This is the first time that the NaI3303 doublet is detected in such high redshift systems. Together with the detection of the MgI2852 transition, this strongly constrains the physical characteristics of the gas. The N(NaI)/N(MgI) ratio is found to be larger than unity, implying that the gas is cool and neutral. The column densities of NaI, CaII, MgI, TiII, MnII and FeII observed at z = 1.1801 are very close to that observed along the line of sight towards 23 Ori in our Galaxy. The shape of the QSO continuum and the relative depletion of Fe, Ti, Mn and Ca are consistent with the presence of dust at z = 1 (AV = 0.5 mag). Altogether it is found that the HI column density at z = 1 is of the order of 1 to 5 10**21 cm-2, the corresponding metallicity is in the range 1--0.3 Zsol. The objects associated with these two systems could both contribute to the lens together with another possible strong system at z = 1.1727 and the strong Lyman-alpha system at z = 2.974. The probable damped Ly-alpha system at z = 2.974 has 19.8 < log N(HI) < 20.3. The transverse dimension of the absorber is larger than 200 pc. Abundances relative to solar are -2.31, -2.26, -2.10, -2.35 and -2.37 for, respectively, Fe, Al, Si, C and O (for log N(HI) = 20.3). (Abridged)
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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.
New optical and infrared observations along the sight-line toward the quasar OI 363 (0738+313) are presented and discussed. Excluding systems which lack confirming UV spectroscopic observations of the actual Lyman alpha line, this sight-line presently contains the two lowest-redshift classical damped Lyman alpha (DLA) quasar absorption line systems known (i.e. with N(HI) ge 2 x 10^{20} atoms cm^{-2}), one at z(abs)=0.0912 and the other at z(abs)=0.2212. The z=0.09 DLA galaxy appears to be an extended low surface brightness galaxy which is easily visible only in infrared images and shows rich morphological structure. Subtraction of the quasar nuclear and host light yields L_K approx 0.08L_K* at z=0.09. The impact parameter between the galaxy and quasar sight-line is very small, b<3.6 kpc (<2 arcsec), which makes measurements difficult. The z=0.22 DLA galaxy is an early-type dwarf with a K-band luminosity of L_K approx 0.1L_K* at impact parameter b=20 kpc. In general, these results serve to support mounting evidence that DLA galaxies are drawn from a wide variety of gas-rich galaxy types. (Abridged)
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).
A very low primordial deuterium abundance of D/H = 1.5 10^{-5} has recently been proposed by Molaro et al. in the Lyman limit system with log(N_HI) = 18.1 cm^{-2} at z_a = 3.514 towards the quasar APM08279+5255. The D/H value was estimated through the standard Voigt fitting procedure utilizing a simple one-component model of the absorbing region. The authors assumed, however, that `a more complex structure for the hydrogen cloud with somewhat ad hoc components would allow a higher D/H. We have investigated this system using our new Monte Carlo inversion procedure which allows us to recover not only the physical parameters but also the velocity and density distributions along the line of sight. The absorption lines of HI, CII, CIV, SiIII, and SiIV were analyzed simultaneously. The result obtained shows a considerably lower neutral hydrogen column density log(N_HI) = 15.7 cm^{-2}. Hence, the measurement of the deuterium abundance in this system is rather uncertain. We find that the asymmetric blue wing of the hydrogen Ly-alpha absorption is readily explained by HI alone. Thus, up to now, deuterium was detected in only four QSO spectra (Q1937-1009, Q1009+2956, Q0130-4021, and Q1718+4807) and all of them are in concordance with D/H = 4 10^{-5}.
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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