arXiv subjects

F. Hamann

Publications and source records attributed to F. Hamann.

45 records · Page 3Linked to original sources

arXiv2001

X-Ray Absorption Associated with High-Velocity UV Absorbers

We present Chandra observations of two radio-quiet QSOs, PG 2302+029 and PG 1254+047. PG 2302+029 has an ultra high-velocity UV absorption system -56,000 km/s, while PG 1254+047 is a Broad Absorption Line (BAL) QSO with detached troughs. Both objects are X-ray weak, consistent with the known correlation between alpha_ox and the strength of the UV absorption lines. The data suggest that there is evidence that both objects are intrinsically weak X-ray sources, in addition to being heavily X-ray absorbed. The X-ray absorption column densities are N_H > 10^22 cm^-2 for neutral gas and the intrinsic emission spectra have alpha_ox > 2. The data are fit best by including ionized (rather than neutral) absorbers, with column densities N_H(PG2302) > 2.98 x 10^22 cm^-2 and N_H(PG1254) > 17.3 x 10^22 cm^-2. The degrees of ionization are consistent with the UV lines, as are the total column densities if the strongest lines are saturated.

astro-ph↗

arXiv2001

Discovery of a 2 Kpc Binary Quasar

LBQS 0103$-$2753 is a binary quasar with a separation of only 0.3 arcsec. The projected spacing of 2.3 kpc at the distance of the source (z = 0.848) is much smaller than that of any other known binary QSO. The binary nature is demonstrated by the very different spectra of the two components and the low probability of a chance pairing. LBQS 0103$-$2753 presumably is a galaxy merger with a small physical separation between the two supermassive black holes. Such objects may provide important constraints on the evolution of binary black holes and the fueling of AGN.

astro-ph↗

arXiv2001

LBQS 0103-2753: A 0.3 Arcsec Binary Quasar

Imaging and spectroscopy with HST show that LBQS 0103-2753 (V = 17.8, z = 0.848) is a binary quasar with a separation of 0.3 arcsec or 2.3 kpc. This is by far the smallest separation binary quasar reported to date. The two components have very different spectra, including the presence of strong broad absorption lines (BALs) in component A only. The emission-line redshifts, based on the broad high ionization C IV lines, are z_A = 0.834 and z_B = 0.858; their difference is 3900 km/s in velocity units. The broad C IV lines, however, are probably not a good indicator of systemic redshift; and LBQS 0103-2753 A and B could have a much smaller systemic redshift difference, like the other known binary quasars. If the systemic redshift difference is small, then LBQS 0103-2753 would most likely be a galaxy merger that has led to a binary supermassive black hole. There is now one known 0.3 arcsec binary among roughly 500 QSOs that have been observed in a way that would reveal such a close binary. This suggests that QSO activity is substantially more likely for black hole binaries at spacings ~2 kpc than at ~15 to 60 kpc. Between 1987 and 1998, the observed Mg II BAL disappeared.

astro-ph↗

arXiv2000

Thomson Thick X-ray Absorption in a Broad Absorption Line Quasar PG0946+301

We present a deep ASCA observation of a Broad Absorption Line Quasar (BALQSO) PG0946+301. The source was clearly detected in one of the gas imaging spectrometers, but not in any other detector. If BALQSOs have intrinsic X-ray spectra similar to normal radio-quiet quasars, our observations imply that there is Thomson thick X-ray absorption (N_H >~10^{24} cm^{-2}) toward PG0946+301. This is the largest column density estimated so far toward a BALQSO. The absorber must be at least partially ionized and may be responsible for attenuation in the optical and UV. If the Thomson optical depth toward BALQSOs is close to one, as inferred here, then spectroscopy in hard X-rays with large telescopes like XMM would be feasible.

astro-ph↗

arXiv1998

Preliminary Analysis of STIS-HST Spectra of Compact Ejecta from Eta Carinae

We describe some preliminary results from spatially-resolved spectroscopy of the compact ejection knots B and D in the Eta Carinae wind. We emphasize various line diagnostics of the abundances, kinematics and physical conditions. The data are from new STIS-HST observations described by Gull et al. elsewhere in this volume.

astro-ph↗

arXiv1998

Elemental Abundances from Intrinsic QSO Emission and Absorption Lines

Several studies have shown that the column densities inferred from broad absorption lines (BALs) require extremely high metallicities and phosphorus overabundances -- apparently in conflict with other abundance diagnostics. Here I use HST spectroscopy of the BALQSO PG 1254+047 to argue that the BALs abundance estimates are incorrect, because partial line-of-sight coverage of the continuum source(s) has led to gross underestimates of the line optical depths and column densities. I claim that the significant presence of PV 1118,1128 absorption in this and other BALQSOs identifies the saturated absorption-line spectrum. This interpretation implies that the total column densities are at least ten times larger than previous estimates, namely log N_H(cm-2) > 22. The outflowing BAL gas, at velocities from -15,000 to -27,000 km/s in PG 1254+047, is therefore a strong candidate for the X-ray absorber in BALQSOs. If this high-column density outflow is radiately accelerated, it must originate <0.1 pc from the QSO.

astro-ph↗

arXiv1997

Partial Coverage and Time Variability of Narrow-Line Intrinsic QSO Absorption Systems

It is possible to distinguish ``intrinsic'' absorption systems (gas clouds within the quasar environment) from ``intervening'' systems (gas clouds unrelated to the quasar phenomenon) by considering certain observational properties. We find that the most direct determinations of the intrinsic nature of a system are time variability and partial coverage of the background light source by the absorption region. Both of these conditions are unlikely to occur in intervening systems. We present Keck and HIRES data which demonstrate both these phenomena. We also summarize a list of several other observational properties which appear to be indicative of ``intrinsic'' systems.

astro-ph↗

arXiv1997

Ionization and Abundances in Intrinsic QSO Absorption-Line Systems

We discuss two aspects of the ionization and abundances in QSO intrinsic absorbers. First, we use the high-ionization doublet Ne VIII 770,780 to test the relationship between the UV line absorbers and the ``warm'' absorbers detected in soft X-rays. In one well-measured QSO with intrinsic z_a ~ z_e lines, UM 675, we estimate that the UV absorber has at least 10 times too little O VII and O VIII to produce the requisite bound-free edges at ~0.8 keV. Second, we show that firm lower limits on the metal-to-hydrogen abundances can be established even with no constraints on the ionization. Those lower limits are typically Z ~> Z_o and sometimes Z ~> 10 Z_o (e.g. for the BALs). We argue that QSO metallicities up to at least ~9 Z_o are consistent with the rapid early-epoch star formation expected in the cores of massive galaxies.

astro-ph↗

arXiv1997

High-Velocity Narrow-Line Absorbers in QSOs

We discuss the identification and kinematics of intrinsic narrow-line absorbers in three QSOs. The line-of-sight ejection velocities in the confirmed intrinsic systems range from 1500 to 51,000 km/s. The ratio of ejection velocity to line width, V/Delta-V, in these systems ranges from ~3 to 60, in marked contrast to the BALs where typically V/Delta-V ~ 1. We speculate on the possible relationship between the BAL and narrow-line absorbers. Like the BALs, intrinsic narrow-line systems appear to be rare, but the outflows that cause them might be common if they cover a small fraction of the sky as seen from the QSO.

astro-ph↗