Isotopic abundance of nitrogen and carbon in distant comets

in Astronomy and Astrophysics (2005), 432(Letters), 5-8

The [SUP]12[/SUP]C[SUP]14[/SUP]N/[SUP]12[/SUP]C[SUP]15[/SUP]N and [SUP]12[/SUP]C[SUP]14[/SUP]N/[SUP]13[/SUP]C[SUP]14[/SUP]N isotopic ratios have been determined in comets C/1995 O1 (Hale-Bopp), C/2001 Q4 ... [more ▼]

The [SUP]12[/SUP]C[SUP]14[/SUP]N/[SUP]12[/SUP]C[SUP]15[/SUP]N and [SUP]12[/SUP]C[SUP]14[/SUP]N/[SUP]13[/SUP]C[SUP]14[/SUP]N isotopic ratios have been determined in comets C/1995 O1 (Hale-Bopp), C/2001 Q4 (NEAT) and C/2003 K4 (LINEAR) at heliocentric distances of, respectively, 2.7, 3.7 and 2.6 AU. These ratios have also been measured at rË 1 AU. No significant differences were found between all determinations, nor with the value obtained for other comets. If confirmed, the discrepancy between the nitrogen isotopic ratios from optical and millimeter measurements on CN and HCN would rule out HCN as a major parent of the cometary CN radicals. Based on observations collected at the European Southern Observatory, Paranal, Chile (ESO Programmes 270.C-5043, 073.C-0525 and 274.C-5015). [less ▲]

Mapping extreme-scale alignments of quasar polarization vectors: evidence for photon-pseudoscalar mixing on cosmological scales?

Poster (2005)

Nitrogen isotopes in comets. Tracking organics from the interstellar medium to the Solar System

Poster (2005)

Polarization properties of broad absorption line QSOs: New statistical clues

in Astronomy and Astrophysics (2004), 427

We report the results of several statistical tests performed on a large sample of 139 broad absorption line (BAL) QSOs with good quality optical spectra and/or optical polarization data. Correlations ... [more ▼]

We report the results of several statistical tests performed on a large sample of 139 broad absorption line (BAL) QSOs with good quality optical spectra and/or optical polarization data. Correlations between ten optical indices and the polarization degree p[SUB]0[/SUB] are systematically searched for. We find six significant non-trivial correlations. In order to identify the most important correlations, we perform a principal component analysis with a sample of 30 BAL QSOs and eight quantities (including p[SUB]0[/SUB]). Most of the variance (Ë 57%) in the data is contained in two principal components called PC1 and PC2. PC1 is mainly dominated by the correlation between the balnicity index BI and the strength of the Fe II emission; it may be driven by the accretion rate of matter onto the central compact object. The variance in PC2 is essentially due to the anti-correlation between p[SUB]0[/SUB] and the detachment index DI, indicating that BAL QSOs with P Cygni profiles (DIâ ª) are usually more polarized than those objects with C IV absorption troughs well detached from the corresponding emission lines (DIâ «). We show that PC2 may be related to the orientation of the BAL QSOs with respect to the line of sight. We also present new spectropolarimetric observations of six BAL QSOs. By adding spectropolarimetric data from the literature, we build a sample of 21 BAL QSOs for which we define four spectropolarimetric indices describing the polarization properties of the absorption and emission lines. We find that the polarization of the C III]] emission line is systematically higher than the polarization of the C IV emission line, and that the highest polarization in the troughs is correlated to the balnicity index. Another important result emerging from the statistical tests performed on this spectropolarimetric sample is a possible anti-correlation between the detachment index and a quantity SI which measures the ratio of the depths of the C IV absorption in the polarized flux and in the total flux. This correlation indicates that in BAL QSOs with P cygni profiles, the BAL troughs in the polarized flux are nearly as deep as in the total flux while, in BAL QSOs with detached absorptions, the BAL troughs in the polarized flux are much weaker than in the total flux. We show that our main results may be explained in the framework of a ``two-component'' wind model which is a natural extension of the classical wind-from-disk models. In this model, the broad absorption occurs in a dense equatorial wind emerging from the accretion disk, while scattering and polarization mainly take place in a polar region. The orientation relative to the observer drives the correlations p[SUB]0[/SUB] - DI and DI - SI. While most of our observations can be explained within this framework, there are also several indications that other polarization mechanisms, and more particularly resonance scattering, may also be at work. Based on observations collected at the European Southern Observatory (ESO, La Silla). Table 1 is only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http: / / cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/427/107 [less ▲]

Polarization in BAL QSOs (Lamy+, 2004)

Textual, factual or bibliographical database (2004)

Table 1 contains optical properties of 139 BAL QSOs. It is essentially a compilation of 93 BAL QSOs coming from large polarization surveys. In addition, we also consider 46 BAL QSOs with good quality ... [more ▼]

Table 1 contains optical properties of 139 BAL QSOs. It is essentially a compilation of 93 BAL QSOs coming from large polarization surveys. In addition, we also consider 46 BAL QSOs with good quality optical (UV rest-frame) spectra but no polarization data. (1 data file). [less ▲]

An MHD-driven Disk Wind Outflow in SDSS J0300+0048?

in AGN Physics with the Sloan Digital Sky Survey. ASPC 311 (2004, June 01)

The outflow in SDSS J0300+0048 has the highest column density yet reported for a broad absorption line quasar. The absorption from different ions is also segregated as a function of velocity in a way that ... [more ▼]

The outflow in SDSS J0300+0048 has the highest column density yet reported for a broad absorption line quasar. The absorption from different ions is also segregated as a function of velocity in a way that can only be explained by a disk wind outflow. Furthermore, the presence of the such large column densities of gas at the high observed outflow velocities may be incompatible with purely radiative acceleration. MHD contributions to the acceleration should be considered seriously. [less ▲]

VLT + UVES spectroscopy of the low-ionization intrinsic absorber in SDSS J001130.56+005550.7

in Astronomy and Astrophysics (2004), 415

We analyse high-resolution VLT+UVES spectra of the low-ionization intrinsic absorber observed in the BAL QSO SDSS J001130.56+005550.7. Two narrow absorption systems at velocities -600 km s[SUP]-1[/SUP ... [more ▼]

We analyse high-resolution VLT+UVES spectra of the low-ionization intrinsic absorber observed in the BAL QSO SDSS J001130.56+005550.7. Two narrow absorption systems at velocities -600 km s[SUP]-1[/SUP] and -22 000 km s[SUP]-1[/SUP] are detected. The low-velocity system is part of the broad absorption line (BAL), while the high-velocity one is well detached. While most narrow absorption components are only detected in the high-ionization species, the lowest velocity component is detected in both high- and low-ionization species, including in the excited Si II[SUP]*[/SUP] and C II[SUP]*[/SUP] lines. From the analysis of doublet lines, we find that the narrow absorption lines at the low-velocity end of the BAL trough are completely saturated but do not reach zero flux, their profiles being dominated by a velocity-dependent covering factor. The covering factor is significantly smaller for Mg II than for Si IV and N V , which demonstrates the intrinsic nature of absorber. From the analysis of the excited Si II[SUP]*[/SUP] and C II[SUP]*[/SUP] lines in the lowest velocity component, we find an electron density ~=10[SUP]3[/SUP] cm[SUP]-3[/SUP]. Assuming photoionization equilibrium, we derive a distance ~=20 kpc between the low-ionization region and the quasar core. The correspondence in velocity of the high- and low-ionization features suggests that all these species must be closely associated, hence formed at the same distance of Ë 20 kpc, much higher than the distance usually assumed for BAL absorbers. Based on observations collected at the European Southern Observatory, Cerro Paranal, Chile (ESO 267.A-5698). [less ▲]

Anomalous Nitrogen Isotope Ratio in Comets

in Science (2003), 301

High-resolution spectra of the CN B[SUP]2[/SUP] Sigma[SUP]+[/SUP]-X[SUP]2[/SUP] Sigma[SUP]+[/SUP] (0,0) band at 390 nanometers yield isotopic ratios for comets C/1995 O1 (Hale-Bopp) and C/2000 WM1 (LINEAR ... [more ▼]

High-resolution spectra of the CN B[SUP]2[/SUP] Sigma[SUP]+[/SUP]-X[SUP]2[/SUP] Sigma[SUP]+[/SUP] (0,0) band at 390 nanometers yield isotopic ratios for comets C/1995 O1 (Hale-Bopp) and C/2000 WM1 (LINEAR) as follows: 165 +/- 40 and 115 +/- 20 for [SUP]12[/SUP]C/[SUP]13[/SUP]C, 140 +/- 35 and 140 +/- 30 for [SUP]14[/SUP]N/[SUP]15[/SUP]N. Our N isotopic measurements are lower than the terrestrial [SUP]14[/SUP]N/[SUP]15[/SUP]N = 272 and the ratio for Hale-Bopp from measurements of HCN, the presumed parent species of CN. This isotopic anomaly suggests the existence of other parent(s) of CN, with an even lower N isotopic ratio. Organic compounds like those found in interplanetary dust particles are good candidates. [less ▲]

VLT+UVES Spectroscopy of the Ca II Low-Ionization Broad Absorption Line Quasar SDSS J030000.56+004828.0

in Astrophysical Journal (2003), 593

We study high-resolution spectra of the ``overlapping-trough'' low-ionization broad absorption line (LoBAL) quasar SDSS J030000.56+004828.0. The Ca II, Mg II, and Mg I column densities in this object are ... [more ▼]

We study high-resolution spectra of the ``overlapping-trough'' low-ionization broad absorption line (LoBAL) quasar SDSS J030000.56+004828.0. The Ca II, Mg II, and Mg I column densities in this object are the largest reported to date for any BAL outflow. The broad Ca II absorption is mildly blended, but the blending can be disentangled to measure the Ca II column density, which is large enough that the outflow must include a strong hydrogen ionization front. The outflow begins at a blueshift of ~1650 km s[SUP]-1[/SUP] from the systemic redshift. The lowest velocity BAL region produces strong Ca II absorption but does not produce significant excited Fe II absorption, while the higher velocity excited Fe II absorption region produces very little Ca II absorption. We have found that only a disk wind outflow can explain this segregation. Whether the outflow is smooth or clumpy, we conclude that the Ca II BAL region has a density high enough to populate excited levels of Fe II but a temperature low enough to prevent them from being significantly populated. This requirement means the Ca II BAL region has T<~1100 K, and perhaps even T<~550 K. This quasar also has an associated absorption line system (AAL) that exhibits partial covering and therefore is likely located near the central engine. Its association with the BAL outflow is unclear. Blending of the AAL with the BAL trough shows that the spatial region covered by the BAL outflow can vary over velocity differences of ~1700 km s[SUP]-1[/SUP]. Based on observations from ESO Director's Discretionary Time program 267.A-5698. [less ▲]

Anomalous 14N/15N ratio in comets 122P/1995 S1 (de Vico) and 153P/2002 C1 (Ikeya-Zhang)

in Bulletin of the American Astronomical Society (2003, May 01), 35

High-resolution (R 60,000) spectra of the Halley-type comet 122P/1995 S1 de Vico (Period 74 years) and the ``intermediate-period" comet 153P/2002 C1 Ikeya-Zhang (P 370 yr) were obtained with the 2DCoude ... [more ▼]

High-resolution (R 60,000) spectra of the Halley-type comet 122P/1995 S1 de Vico (Period 74 years) and the ``intermediate-period" comet 153P/2002 C1 Ikeya-Zhang (P 370 yr) were obtained with the 2DCoude spectrograph at the 2.7-m Harlan J. Smith telescope of the McDonald Observatory. These comets were within 1 AU from the Sun (0.66 and 0.92 AU, respectively). The spectra display CN (0,0) bands indicating an anomalous [SUP]14[/SUP]N/[SUP]15[/SUP]N isotope ratio, in the sense that it is close to half the value in Earth's atmosphere (the so-called ``Solar system value") and about half that obtained in comet Hale-Bopp from sub-millimeter measurements on HCN, generally believed to be the main parent of CN. Similar conclusions had been reached for C/1995 O1 (Hale-Bopp), an ``old long-period", and for C/2000 WM1 (LINEAR), a ``young long-period" comet. As suggested by Arpigny et al. (2003), this apparent abundance anomaly points towards the existence of other unknown parent(s) of CN, with an even higher [SUP]15[/SUP]N excess. Organic compounds like those found in interplanetary dust particles (IDPs) are good candidates. The similarity between comets of different dynamical ages is pointed out. 1 Research Director FNRS (Belgium) 2 Research Associate FNRS (Belgium) [less ▲]