Detailed Monte Carlo inversion analysis of the spectral lines from three Lyman limit systems (LLSs) [N(H ) ≳ 1.0 × 1017 cm-2] and nine lower N(H ) systems [2 × 1014 cm-2 ≲ N(H ) ≲ 2 × 1016 cm-2] observed in the Very Large Telescope/UV-Visual Echelle Spectrograph spectra of Q0347-3819 (in the range 2.21 ≤ z ≤ 3.14) and of APM BR J0307-4945 (at z = 4.21 and 4.81) is presented. Combined with the results from a previous work, the analyzed LLSs show that they are a heterogeneous population originating in different environments. A functional dependence of the line-of-sight velocity dispersion σv on the absorber size L is confirmed: the majority of the analyzed systems follow the scaling relation σv ~ (NHL)0.3 (with NH being the total gas column density). This means that most absorbers may be related to virialized systems such as galaxies or their halos. Previously noted enhancement of the metal content in small-size systems is also confirmed: metallicities of Z ~ Z☉ are found in systems with L ≲ 0.4 kpc, whereas we observe much lower metal abundances in systems with larger linear sizes. For the first time in LLSs, a pronounced [α-element/iron peak] enrichment is revealed: the absorber at zabs = 2.21 shows [O/Fe] = 0.65 ± 0.11, [Si/Fe] = 0.51 ± 0.11, and [Mg/Fe] = 0.38 ± 0.11. Several absorption systems exhibit characteristics that are very similar to those observed in high-velocity clouds (HVCs) in the Milky Way and may be considered as high-redshift counterparts of Galactic HVCs.

view Abstract Citations (7) References (53) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Hydrodynamic Collapse of Protogalaxies to LY alpha Disks Schiano, A. V. R. ; Wolfe, A. M. ; Chang, C. A. Abstract A series of two-dimensional, Eulerian hydrodynamic simulations of the formation of disk galaxies is presented. These simulations are used to test the hypothesis that high-redshift damped Lyα absorption systems detected in QSO spectra (Wolfe and coworkers) originate in large (R > 3 R_H_0__), massive disks of gas which are the progenitors of present-day galactic disks. We assume that the disks form out of collapsing gas in extended halos of nondissipative matter. The gas starts out with the same density distribution as the halo, i.e., as a gaseous corona, but collapses as a result of radiative cooling. Assuming axisymmetry about the spin axis, we numerically integrate the hydrodynamical and gravitational field equations in one quadrant of the meridional plane. In the first stage of the calculations the time evolution of the flow is followed until the gaseous disk which forms is centrifugally supported. Our results reveal hydrodynamic phenomena such as pancaking, accretion shocks, and contact discontinuities. For a wide range of input parameters a dislike structure approached centrifugal equilibrium in less than ~ 2 Gyr after the start of collapse. In agreement with earlier studies, the final size of the disk depends on the spin parameter. For a fixed spin parameter, the size also depends on the core radius of the halo; the disk radius increases with core radius. The model disks were subject to ring-forming gravitational instabilities unless the disk gas was prevented from cooling below 10^5^ K. We also find that gaseous halos with metallicities substantially below 10% solar abundance cannot cool rapidly enough to form disks by z > 2. In the second stage of the calculation we considered a specific mechanism for contraction of the centrifugally supported disk: we were motivated by evidence that damped Lyα absorption systems evolve into current disks with R ~ R_H_0__. We show how mass shed by an assumed population of halo stars reaches the plane ~ 1 Gyr after formation of the initial disk, and how this causes the disk to contract by a factor of more than 2 after another 1 Gyr, i.e., the contraction is completed in ~ 3 Gyr after the start of collapse. Publication: The Astrophysical Journal Pub Date: December 1990 DOI: 10.1086/169498 Bibcode: 1990ApJ...365..439S Keywords: Disk Galaxies; Galactic Structure; Gravitational Collapse; Hydrodynamic Equations; Lyman Alpha Radiation; Quasars; Computational Astrophysics; Gas Flow; Gravitational Fields; Red Shift; Astrophysics; GALAXIES: FORMATION; GALAXIES: STRUCTURE; HYDRODYNAMICS; QUASARS full text sources ADS |

view Abstract Citations (27) References (26) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Effect of a Quasi-stellar Object on Its Host Galaxy: Dynamical and Physical Processes in the Interstellar Medium around a Quasi-stellar Object Chang, C. A. ; Schiano, A. V. R. ; Wolfe, A. M. Abstract The dynamical and physical processes in the ISM around a QSO have been calculated in order to understand the effects of QSO radiation on the host galaxy. Numerical hydrodynamical solutions for one- and two-dimensional cases are found through a MacCormack differencing scheme. Ion-field emission, ion sputtering, charge equilibrium, thermal equilibrium, coupling between gas ions and dust grains, photoionization, and photoelectrical processes are considered. The results show that dust grains play an important role in determining the dynamics of the ISM around a QSO. Inside 7 kpc, all dust grains are destroyed in about 30 million yr. Gas goes to large distances in the galactic plane and leaves the galaxy. Publication: The Astrophysical Journal Pub Date: November 1987 DOI: 10.1086/165714 Bibcode: 1987ApJ...322..180C Keywords: Fluid Dynamics; Interstellar Matter; Quasars; Radiation Distribution; Spiral Galaxies; Astronomical Maps; Boundary Value Problems; Mass Distribution; Plasma Heating; Astrophysics; HYDRODYNAMICS; INTERSTELLAR: GRAINS; INTERSTELLAR: MATTER; QUASARS; RADIATION MECHANISMS full text sources ADS |

view Abstract Citations (646) References (50) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Damped Lyman-Alpha Absorption by Disk Galaxies with Large Redshifts. I. The Lick Survey Wolfe, A. M. ; Turnshek, D. A. ; Smith, H. E. ; Cohen, R. D. Abstract As a first step in a survey for remote galaxies, low-resolution (delta lambda = 10 angstroms) spectra of 68 high-redshift QSOs were obtained. The idea is to locate the large column density of neutral hydrogen in the disks of foreground galaxies through the detection of Ly-alpha absorption lines broadened by radiation damping. The damped lines are valuable signatures of high-r-redshift galaxies, since they are predicted to much stronger than Ly-alpha absorption lines typically found in the spectra of QSOs. A list of absorption features that are candidates for 'Ly-alpha disks'. The spectra of all 68 QSOs are presented as plots of flux vs wavelength along with the 1-sigma error in flux vs wavelength. The plots also designate absorption features that are located blueward of Ly-alpha emission and deemed to be significant by criteria that are given. Fifteen absorption features are seen to be damped Ly-alpha, and 10 are blends of multiple narrow components that are separated by Doppler velocities of about 1000 km/s. Preliminary evidence indicates that the damped lines and the multicomponent lines are drawn from distinct populations of absorbers. Publication: The Astrophysical Journal Supplement Series Pub Date: June 1986 DOI: 10.1086/191114 Bibcode: 1986ApJS...61..249W Keywords: Absorption Spectra; Disk Galaxies; Lyman Alpha Radiation; Quasars; Red Shift; Astronomical Catalogs; Galactic Evolution; Spectrum Analysis; Astrophysics; QUASARS; SPECTROPHOTOMETRY full text sources ADS | data products SIMBAD (69) NED (65) Related Materials (2) Part 2: 1989ApJ...344..567T Part 3: 1993ApJ...404..480W

A new type of survey for galaxies with z > 2 will be described. The idea is to search for the spectroscopic imprint that the H1 disc of a foreground galaxy leaves on radiation emitted by a background Qso; namely, a Lyman-α absorption line broadened by radiation damping. A continuing survey has revealed the presence of 15 damped Lα lines with redshifts between 1.8 and 2.8 in the spectra of 68 QSOS. In comparison, no more than three discs with the properties of nearby galaxies should have been detected. Furthermore, the mean column density of the 15 absorbers, <(N(H1)> = 1.4 x 10 21 cm -2 , is much larger than expected for the outskirts of H1 discs. Both statistical and physical evidence has accumulated which suggests that the damped Lα systems are a distinct population of absorbers with properties reminiscent of H1 discs. First, the Lyman-α absorption lines detected in the survey follow a frequency distribution of equivalent width that cannot be due to previously detected cloud populations. At large equivalent widths, where the damped Lα lines occur, a new population of absorbers must exist. This damped population is therefore unrelated to clouds that are known to differ physically from galaxy discs. Secondly, detailed studies of the damped population reveal many of the properties shared by the H1 discs of galaxies. For example, ( a ) the absorption spectra due to ions of abundant elements are dominated by low ions such as C + , Si + and Fe + , instead of C3 + and Si 3+ , which are usually seen and ( b ) the recent detection of 21 cm absorption at z = 2.04 in one of the damped systems shows that the H1 is cold and that it has a low level of turbulence (σ ≈ 10 km s -1 ). Another piece of evidence connecting the damped population with discs is that the cosmological mass density of the absorbers is characterized by a density parameter, Ω≈ 3 x 10 -3 / h . This is comparable to the Ω due to luminous baryons. We suggest that this agreement is not coincidental, but rather reflects the fact that we have detected the progenitors of the baryon content of nearby galaxies. The discovery of the damped population has a number of implications for theories of galaxy formation. First, if the damped absorbers are identified with the normal population of galaxies, the H1 discs at z > 2 have radii ≈ 3 R HO (Holmberg). Because their redshift distribution is consistent with formation at z > 2.8, the production of large H1 discs from the collapse of protogalaxies must occur more rapidly (within less than 3 Ga) than predicted in many theories. Secondly, the collapse to discs of present size must occur in the galactic plane rather than from the halo.

view Abstract Citations (35) References (31) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Magnesium, iron and calcium in the z=0.39498 21 centimeter absorber of PKS 1229-021. Briggs, F. H. ; Turnshek, D. A. ; Schaeffer, J. ; Wolfe, A. M. Abstract Sensitive observations of the Fe II, Mg I, Mg II, and Ca II lines in the spectrum of PKS 1229-021 at z = 0.39498 with the Multiple Mirror Telescope confirm previous deductions about the velocity structure of the absorber that were based on curve-of-growth analysis of optical data and the width of the 21 cm absorption profile. The velocity and opacity structure conforms to a multicloud picture where the line of sight to the QSO encounters both the disk and the halo of an intervening galaxy. The new observations also find a Mg I line of 'normal' strength in contrast to earlier observations. No Ca II lines are detected. Publication: The Astrophysical Journal Pub Date: June 1985 DOI: 10.1086/163244 Bibcode: 1985ApJ...293..387B Keywords: Absorption Spectra; Astronomical Spectroscopy; Calcium; Extragalactic Radio Sources; Iron; Magnesium; Quasars; Abundance; Centimeter Waves; Emission Spectra; Opacity; Astrophysics full text sources ADS | data products NED (2) SIMBAD (1)

view Abstract Citations (79) References (11) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Detection of 21 centimeter absorption at Z = 2.04 in the QSO PKS 0458-02. Wolfe, A. M. ; Briggs, F. H. ; Turnshek, D. A. ; Davis, M. M. ; Smith, H. E. ; Cohen, R. D. Abstract The paper reports the detection of 21 cm absorption at the redshift z = 2.03945 + or - 0.00008 in the radio continuum of the QSO PKS 0458-02. This is the largest redshift yet found at radio wavelengths. It corresponds to an optical redshift inferred from damped Ly-alpha and C II, C II(asterisk), and Si IV absorption. The 21 cm spectrum reveals two narrow and deep components. Comparison with the column density inferred from Ly-alpha reveals that the spin temperature is less than 1000 K. It is shown that each component cannot arise in a single pressure-confined cloud. Rather, it is suggested that the absorption site is a highly redshifted galactic disk, or possibly two isolated, self-gravitating clouds. Publication: The Astrophysical Journal Pub Date: July 1985 DOI: 10.1086/184511 Bibcode: 1985ApJ...294L..67W Keywords: Absorption Spectra; Centimeter Waves; Galaxies; Quasars; Radio Sources (Astronomy); Disks (Shapes); Lyman Alpha Radiation; Radio Spectra; Red Shift; Astrophysics full text sources ADS | data products SIMBAD (1) NED (1)

view Abstract Citations (59) References (28) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The broad absorption lines in the spectrum of the QSO PKS 1157+014 : a possible link between broad absorption line QSOs, metal enrichment, and the formation of galaxies. Briggs, F. H. ; Turnshek, D. A. ; Wolfe, A. M. Abstract A high column density, low velocity dispersion absorption system detected in the H I 21-cm transition can largely account for the broad absorption trough to the blue of the Lyman-alpha emission redshift in the spectrum of the QSO PKS 1157 + 014, and the apparent deficiency of Lyman-alpha emission at z(em) = 1.978 is due to attenuation by the damping wings of the z = 1.94362 system rather than to an intrinsic absence. The large velocity spread of the broken high ionization troughs makes study of this QSO relevant to the Broad Absorption Line (BAL) type QSO problem. The optical spectrum morphology of PKS 1157 + 014 places it midway between the radio-weak BAL class and a group of radio-bright QSOs with 'associated' absorption complexes. It is suggested that BAL QSOs play a role in both metal enrichment of the intergalactic medium and the triggering of galaxy formation. Publication: The Astrophysical Journal Pub Date: December 1984 DOI: 10.1086/162713 Bibcode: 1984ApJ...287..549B Keywords: Absorption Spectra; Galactic Evolution; Lyman Spectra; Metallicity; Quasars; Radio Sources (Astronomy); Intergalactic Media; Morphology; Astrophysics full text sources ADS | data products SIMBAD (1) NED (1)

view Abstract Citations (31) References (16) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Why high-latitude clouds in our galaxy and the highly redshifted clouds observed in front of QSOs do not belong to the same parent population. Wolfe, A. M. Abstract International Ultraviolet Explorer observations of high-latitude gas in our Galaxy reveal the presence of both C II and C IV absorption in the spectra of stars with z greater than 2 kpc. On the other hand, C II is generally absent from unbiased samples of QSO redshift sytems with C IV absorption. Comparisons between the equivalent-width distributions of the QSO sample and of the galactic sample (which is suitably corrected for contamination by disk absorption) shows that the probability that the two samples are drawn from the same parent population is less than 1 percent for C II and less than 10 percent for C IV. Thus, contrary to prevailing opinion, it is highly unlikely that gaseous halos comprised of material with properties of the high-latitude gas are responsible for the bulk of known QSO redshift systems. However, gaseous halos with bimodal states of ionization, or in which the ionization state is a unique function of redshift, are compatible with QSO absorption statistics. Publication: The Astrophysical Journal Pub Date: May 1983 DOI: 10.1086/184018 Bibcode: 1983ApJ...268L...1W Keywords: Cosmic Gases; Intergalactic Media; Milky Way Galaxy; Quasars; Ultraviolet Astronomy; Astronomical Spectroscopy; Ionization; Iue; Red Shift; Spectrum Analysis; Astrophysics full text sources ADS | data products SIMBAD (7) NED (3) MAST (1) Related Materials (1) Erratum: 1983ApJ...271L..43W

view Abstract Citations (120) References (53) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The incidence of 21 centimeter absorption in QSO redshift systems selected for MG II absorption : evidence for a two-phase nature of the absorbing gas. Briggs, F. H. ; Wolfe, A. M. Abstract A search for 21 cm absorption in the continua of 15 radio-bright QSOs reveals that 21 cm absorption occurs in two out of 18 redshifted clouds selected for Mg II absorption. There is no evidence that optical properties such as Mg II equivalent width, Mg II doublet ratio, or Mg I equivalent width are correlated with 21 cm optical depth. Although the unsaturated appearance of the Mg II doublet detected at z = 0.395 in 1229-021 indicates that this absorber should be transparent to 21 cm radiation, it is one of two systems found to exhibit 21 cm absorption. The lack of correlation between optical and radio absorption properties is related to the multi- component nature of the absorbing gas. While most of the narrow velocity components detected in this gas may not contain enough H I to produce 21 cm absorption, they still dominate saturated equivalent widths of UV resonance lines owing to the large internal velocity interval which they span. Occasionally, most of the H I is in one or more narrow components which produce detectable 21 cm absorption, but which make negligible contribution to optical equivalent widths. Lower limits are placed on the spin temperature of three Mg II systems, which rule out galactic disks as the absorption sites. A two-phase model is suggested to unify the entire sample of Mg II systems. It is likely that the thick phase is comprised of clouds in galactic disks which produce 21 cm absorption, while thin-phase clouds are transparent to 21 cm radiation and reside in galactic halos. The Mg II systems differ depending on how much gas is encountered along the line of sight in each phase. Comparison of the small cross section of the disk with the larger cross section of the halo explains why the incidence of 21 cm absorption in the Mg II systems is so rare. Publication: The Astrophysical Journal Pub Date: May 1983 DOI: 10.1086/160931 Bibcode: 1983ApJ...268...76B Keywords: Absorption Spectra; Centimeter Waves; Cosmic Gases; Magnesium; Quasars; Radio Sources (Astronomy); Red Shift; Abundance; Astronomical Models; Astronomical Spectroscopy; Galactic Structure; Hydrogen; Very Long Base Interferometry; Visible Spectrum; Astrophysics full text sources ADS | data products SIMBAD (19) NED (13)

view Abstract Citations (61) References (19) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Detection of 21 centimeter absorption at z = 1.94 in the QSO PKS 1157+014. Wolfe, A. M. ; Briggs, F. H. ; Jauncey, D. L. Abstract We report the detection of 21 cm absorption by neutral hydrogen in front of PKS 1157+014, a QSO with emission redshift Zem = 1.978 ± 0.008. The absorption line arises at 482.537 ± 0.002 MHz, corresponding to a redshift Zabs = 1.94362 ± 0.00001 that is identical, within observational errors, to the previously detected optical redshift of absorption system d. The coincidence between radio and optical redshifts reinforces the case for uniformity of physical laws throughout most of spacetime. The presence of several other absorption systems, along with this one, spanning a range in Zabs corresponding to velocities from +1000 to -8500 km s-1 suggests that this system, along with the others, is ejected from QSO. However, the determination of the spin temperature Ts from a comparison of Lyα and 21 cm absorption spectra argues against this interpretation. Our upper limit of Ts < 470 K places system d farther than 10 kpc from the QSO to avoid excitation effects of the 21 cm continuum. At this distance the absorption system requires 100 times more radiative momentum than the QSO can offer. Instead, we suggest that system d is part of an H I disk of a galaxy gravitationally bound to a cluster containing the QSO. Publication: The Astrophysical Journal Pub Date: September 1981 DOI: 10.1086/159170 Bibcode: 1981ApJ...248..460W full text sources ADS | data products SIMBAD (4) NED (1)

view Abstract Citations (31) References (28) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The effect of L-alpha radiation on the spin temperature of gas ejected from QSOs Urbaniak, J. J. ; Wolfe, A. M. Abstract Twenty-one centimeter radiation emitted by QSOs can drive the spin temperature of neighboring H I clouds above their local kinetic temperatures. The consequent decrease in 21-cm opacity makes these ejected clouds unlikely sites for 21-cm absorption unless Lyman-alpha radiation generated by the same QSO is bright enough to determine the hyperfine level populations of the local hydrogen. This paper considers how the Lyman-alpha is produced and transported, and how it affects the spin temperature of an ejected cloud. It is found that photoionization of the absorber by Lyman continuum radiation emitted by the QSO results in Lyman-alpha production in the ionized H II portion of the absorber. In addition, it is shown that all solutions to the transfer equation predict characteristic double-hump emission features in the emergent spectrum. Publication: The Astrophysical Journal Pub Date: March 1981 DOI: 10.1086/158717 Bibcode: 1981ApJ...244..406U Keywords: Gas Temperature; Hydrogen Clouds; Lyman Alpha Radiation; Quasars; Spin Temperature; Centimeter Waves; Ejecta; Fine Structure; Hyperfine Structure; Kinetic Energy; Molecular Energy Levels; Numerical Analysis; Stellar Mass Ejection; Transport Properties; Astrophysics full text sources ADS |

view Abstract Citations (36) References (11) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Evidence for large-scale uniformity of physical laws Tubbs, A. D. ; Wolfe, A. M. Abstract Consideration is given to the coincidence of redshifts deduced from 21 cm and resonance transitions in absorbing gas detected in front of four quasi-stellar objects which results in stringent limits on the variation of the product of three physical constants both in time and space. It is found that (sigma-squared) (gp) (m/M), where gp is the proton gyromagnetic ratio, is spatially uniform, to a few parts in 10,000, throughout the observable universe. These limits are shown to be largely model independent, relying only upon the cosmological interpretation of redshifts and the isotropy of the 3 K background radiation. It is concluded that a quantity as complex as gp being uniform throughout most of spacetime, even in causally disjoint regions, suggests that all physical laws are globally invariant. Publication: The Astrophysical Journal Pub Date: March 1980 DOI: 10.1086/183208 Bibcode: 1980ApJ...236L.105T Keywords: Big Bang Cosmology; Constants; Galactic Radiation; Quasars; Red Shift; Absorption Spectra; Astrophysics; Background Radiation; Space-Time Functions; Universe; Astrophysics full text sources ADS | data products NED (4)

view Abstract Citations (86) References (47) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS First results of a sensitive search for H I envelopes in a complete sample of spiral galaxies : extensive H I near the isolated SC I NGC 628. Briggs, F. H. ; Wolfe, A. M. ; Krumm, N. ; Salpeter, E. E. Abstract Preliminary results of a search with the Arecibo 1000-foot (305-m) telescope for extended H I envelopes surrounding spiral galaxies show that column densities of H I greater than or equal to 3 x 10 to the 18th/sq cm at 2-3 Holmberg radii are not common. The sample includes all galaxies of Hubble type later than S0, with optical major-axis diameter greater than 7 arcmin, and with declination 3-35 deg, and recessional velocity greater than 200 km/s. The prevalent upper limit to H I column density suggests that these outer regions (radius greater than two Holmberg radii) cannot form QSO-like Mg II absorption lines unless the abundance of Mg is at least 10 times that observed in the interstellar medium or in Population II regions of the Galaxy. The isolated Sc I galaxy NGC 628 is an exceptional case. This large, face-on galaxy shows H I emission extending asymmetrically to the SW as far as 3 Holmberg radii. Publication: The Astrophysical Journal Pub Date: June 1980 DOI: 10.1086/158007 Bibcode: 1980ApJ...238..510B Keywords: Centimeter Waves; Hydrogen Clouds; Interstellar Gas; Radio Astronomy; Radio Sources (Astronomy); Spiral Galaxies; Abundance; Data Processing; Hydrogen Atoms; Magnesium; Astrophysics full text sources ADS | data products SIMBAD (13) NED (13)

view Abstract Citations (10) References (4) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Further VLB observations of the redshifted H I absorption in AO 0235+164. Johnston, K. J. ; Broderick, J. J. ; Condon, J. J. ; Wolfe, A. M. ; Weiler, K. ; Genzel, R. ; Witzel, A. ; Booth, R. Abstract VLB observations of the 932 MHz H I absorption line and continuum of the BL Lacertae object AO 0235 + 164 with projected baselines of 1.8 x 10 to the 7th lambda have failed to reveal any transverse spatial differences between the emitting and absorbing regions. The apparent source size is probably not broadened by scattering in the absorbing region. A 3 rms upper limit of 0.12 km/s to the velocity change of the absorber between 1976 December and 1977 July was set. The corresponding acceleration of less than 1 x 0.001 cm/sq s indicates that the absorbing region is probably more than 3 kpc away from the continuum source. Publication: The Astrophysical Journal Pub Date: December 1979 DOI: 10.1086/157515 Bibcode: 1979ApJ...234..466J Keywords: Absorption Spectra; Bl Lacertae Objects; Hydrogen Clouds; Radio Sources (Astronomy); Red Shift; Very Long Base Interferometry; Line Spectra; Neutral Gases; Radial Velocity; Astrophysics; BL Lacertae Objects:H I Absorption; BL Lacertae Objects:VLB Interferometry full text sources ADS | data products SIMBAD (1) NED (1)

view Abstract Citations (55) References (29) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A comprehensive radio study of the z = 0.524 absorption system in AO 0235+164. Wolfe, A. M. ; Broderick, J. J. ; Condon, J. J. ; Johnston, K. J. Abstract We present pencil-beam and VLB observations of the 932 MHz absorption line and continuum of the BL Lacertae object AO 0235+164, and pencil-beam observations of its 318 and 430 MHz continuum. We find that this redshifted (z = 0.524) 21 em line consists of many narrow components with r > 0.002 that are spread over a velocity range of 105 km i A comparison with the z = 0.524 optical absorption spectrum suggests that both types of lines arise in the same material rather than in two distinct regions as suggested by previous radio spectra. This leads to a determination of element abundances relative to hydrogen and a reevaluation of limits on the variation of certain physical constants over cosmic time scales. The VLB continuum fringe visibility implies a source angular diameter O < 0'.'006. The VLB phase and amplitude spectrum shows lines of the same optical depth as the pencil-beam profile and the lack of any phase shift between line and continuum. If the absorption arises in a galaxy like our own, the VLB line data indicate O < 0'.'0027. The resulting limit on the 932 MHz brightness temperature is Tb(932)> 1012 K, which may violate the Compton limit. The low4requency continuum data show that the 300-400 MHz flux has changed by a factor of 2 in 3 years, making AO 0235+164 the most active known low-frequency variable. If AO 0235+164 is cosmologically distant, this source must either expand relativistically or emit coherently. All the data available indicate that the z = 0.524 absorption system is extremely difficult to understand in terms of ejection from AO 0235+164. Our data are consistent with absorption by an intervening galaxy with a cosmological red shift of z = 0.524, but do not exclude the possible association of the BL Lacertae object with the z = 0.524 absorber. Subject headings: BL Lacertae objects - cosmology - radio sources: 21 em radiation - radio sources: variable Publication: The Astrophysical Journal Pub Date: June 1978 DOI: 10.1086/156195 Bibcode: 1978ApJ...222..752W Keywords: Absorption Spectra; Cosmology; Radio Sources (Astronomy); Ultrahigh Frequencies; Hydrogen Clouds; Infrared Absorption; Molecular Absorption; Radiant Flux Density; Red Shift; Astrophysics; BL Lacertae Objects:Radio Radiation; BL Lacertae Objects:Redshifts full text sources ADS | data products SIMBAD (3) NED (1)

view Abstract Citations (54) References (17) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS 3C 286: a cosmological QSO? Wolfe, A. M. ; Broderick, J. J. ; Condon, J. J. ; Johnston, K. J. Abstract Very-long-baseline (VLB) interferometer observations of the 839-MHz absorption line in the QSO 3C 286 were made. The absorbing region was resolved and is at least 0.02 arcsec across, independent of any continuum brightness distribution model. The observed amplitude and phase spectra were decomposed into amplitude absorption spectra of the two strongest components in the best available model of 3C 286. The line in front of each component is quite narrow, and the line centers are separated by only 3 km/s in velocity. These observations are not inconsistent with absorption by an intervening galaxy, but they eliminate several cases in which the absorption is intrinsic, including photon-driven shells and gravitational redshifts. Publication: The Astrophysical Journal Pub Date: September 1976 DOI: 10.1086/182230 Bibcode: 1976ApJ...208L..47W Keywords: Absorption Spectra; Interferometry; Quasars; Cosmology; Electromagnetic Absorption; Interstellar Matter; Red Shift; Ultrahigh Frequencies; Astrophysics full text sources ADS |

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view Abstract Citations (53) References (39) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Physical conditions and the location of the absorption-line systems in the QSO 3C 286 and the BL Lacertae object PKS 0735+178. Wolfe, A. M. ; Burbidge, G. R. Abstract The redshifted 21-cm and Mg ii absorption lines observed in the QSO 3C 286 and the BL Lacertae object 0735 + 178, respectively, are analyzed to determine the location of the absorbing gas. We first describe evidence which supports the presence of neutral hydrogen intrinsic to QSOs, and then examine excitation conditions influencing the formation of 21-cm absorption lines. Due to the high spin temperature Ts resulting from the bright 21-cm continuum, the 21-cm absorption line observed in 3C 286 can arise close to the QSO only if La radiation determines the excitation of the hyperfine levels. The 21-cm line could also form in an intervening galaxy. The absence of redshifted Mgii absorption in the spectrum of 3C 286 places an upper limit of 3 x 10-3/T8 on the Mg+/H I ratio in the column of absorbing Hi. This is compatible with a solar abundance ratio of Mg/H; but if the observed upper limit to Mgii absorption were reduced by a factor 2, this would require Mg+/Hi < l0-2(Mg/H)0. An analysis of the Mgii absorption lines seen in 0735 + 178 leads to two possibilities: (a) a large column density of Mg+ ions and low velocity dispersion; or (b) a low column density and large velocity dispersion. Wbereas (b) is kinematically inconsistent with an intervening galaxy, (a) is not. We propose that 21-cm absorption features be searched for in the 30-cm continuum of 0735 + 178. If no absorption is seen, and (a) applies, then the spin temperature must be much higher than that observed in absorbing clouds in our Galaxy, thus making an intervening galaxy implausible. Subject headings:BL Lacertae objects infrared sources quasi-stellar sources or objects 21-cm radiation Publication: The Astrophysical Journal Pub Date: September 1975 DOI: 10.1086/153821 Bibcode: 1975ApJ...200..548W Keywords: Absorption Spectra; Line Spectra; Quasars; Infrared Astronomy; Intergalactic Media; Metal Ions; Red Shift; Astrophysics full text sources ADS | data products NED (2)

view Abstract Citations (25) References (56) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS On the Steady Flow of Gas from the Nuclei of Seyfert Galaxies Wolfe, Arthur M. Abstract Heating of gas by energy released during explosive events produces hot (T 5 x 106 K) winds in Seyfert nuclei. Steady-state solutions indicate that supersonic velocities up to 800kms-' are obtainable. Lyman continuum radiation emitted by the wind ionizes and maintains temperature ofcooler (T 10 K) gas clouds seen in emission, and dominates energy losses during early stages of expansion. A study of stability of the thermal equilibrium state leads to a two-component model: a hot stable phase (the wind), in pressure equilibrium with a cooler stable phase (clouds). Extreme variations in cloud electron densities are a consequence of the steep decrease with radius of external pressure. Cloud dynamics are related to the radius of formation and internal parameters. Permitted lines of H are emitted by high-density clouds formed at the base of the wind, while forbidden lines arise in radially moving clouds, produced throughout the wind. It is shown that one of the latter clouds seen in projection against the nonstellar continuum can explain observed, blueshifted absorption lines. Effects of the wind upon the central galactic region, such as the sweeping out of interstellar H0, the radial motions of spiral arms, and the production of large-scale turbulent clouds, are also considered. Subject headings: galaxies - Seyfert galaxies Publication: The Astrophysical Journal Pub Date: March 1974 DOI: 10.1086/152711 Bibcode: 1974ApJ...188..243W full text sources ADS | Related Materials (1) Addendum: 1974ApJ...188..441W