The ISO-IRAS Faint Galaxy Survey will obtain comprehensive space- and ground-based observations of the most distant and luminous galaxies in the IRAS Faint Source Survey. ISO observations are obtained by filling short gaps in the ISO observing schedule with pairs of 11.5 mu m ISOCAM. and 90 mu m ISOPHOT observations. As of the October 1997 date of this Conference, over 500 sources have been observed by ISO with an ISOCAM detection rate exceeding 80%. Ground-based spectrophotometry confirms that the IIFGS efficiently detects moderate-redshift, strong emission line Luminous Infrared Galaxies. Spectrophotometry is currently available for 67 galaxies with 0.07 < z < 0.7 and L-fir > 10(11)L.. The galaxies are comparable to nearby LIGs, showing HII/Liner excitation; about 10% exhibit strong AGN characteristics. As a part of this survey we will cover over 1.25 square degrees of sky to an 11.5 mu m limit of approximately 1.0mJy, allowing a sensitive estimate of the 11.5 mu m logN-logS Relationship. Preliminary 11.5 mu m source counts suggest substantial evolution in the mid-infrared galaxy population.

A broad emission feature, with a velocity width of the order of 5000 km s-1^, has been observed near rest wavelength 3870 A in the spectra of three low-redshift QSOs. We identify the line as [Ne III] λ3869 and suggest the presence of a significant amount of gas at a density 108-9^ cm-3^ in the vicinity of the central source. This broad line may have varied over a time scale of two years, indicating that clouds of intermediate density between 108-11^ cm-3^ may coexist in the broad- line region. Such clouds would be optically thin, highly ionized, and subject to rapid destruction by radiation pressure.

The strong self-damped Lyman α absorption systems present in the spectra of high redshift QSOs represent a unique population of absorber which has recently been associated with the precursors of current disk galaxies. In a low resolution survey for what we have come to call “Lyman α disk systems” performed at Lick Observatory (Wolfe, et al. 1986, Ap. J. Suppl. 61, 249) approximately 18 systems with confirmed damped Lyman α profiles and rest frame equivalent widths greater than 5 Å were detected in a sample of 68 high redshift QSOs (Smith, Cohen and Bradley 1986, Ap. J. 310, 583). Subsequent higher resolution study has shown these systems to have the following properties (Turnshek, et al. 1988, Ap. J., in press): 1.Neutral hydrogen column densities, 2 × 1020 ≤ NHI ≤ 8 × 1021 cm−2.2.Low-mixed ionization state. Typically the low ionization states dominate the high ionization states (e.g. CII ≫ CIV). Some enrichment has occurred, −2≲[X/H]⊙ ≲0.3.Gas density, n ≲ 1 cm−3.4.The gas shows two components, a quiescent (disk) component, σν ≲ 10 km s−1, and a turbulent (halo) component, σν ≲ 20 km s−1. Some systems show only the low velocity dispersion component.5.At least one system intervening toward a radio QSO (Pks 0458-020) shows 21-cm absorption. The system shows multiple cloud structure with σν ≈ 6 km s−1, Ts ≈ 100 K, and structure extended over several kpc on the sky.6.There is evidence that these systems may be self gravitating with scale height of the order of 300 pc.7.These systems represent a unique population of absorber (distinct from the ‘Lyman a forest’ and heavy element systems) covering approximately 20% of the sky to z ≈ 3 and accounting for all of the baryonic matter at that redshift.

view Abstract Citations (52) References (65) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS LY alpha Emission from Disk Absorption Systems at High Redshift: Star Formation in Young Galaxy Disks Smith, Harding E. ; Cohen, Ross D. ; Burns, Joseph E. ; Moore, David J. ; Uchida, Barbara A. Abstract We report narrow-band imaging observations made in an attempt to detect Lyα emission from high-redshift candidate galaxy disk systems discovered as high column density absorbers of background QSOs. For four systems, with z = 2.3-2.8, no emission is detected to a limit of approximately 10^-16^ ergs cm^-2^ s^-1^ (3 σ), corresponding to luminosity limits L(Lyα) <~ 10^42-43^ ergs s^-1^ for the material producing this absorption. (A detection of Lyα emission from the z = 2.3 absorber in front of PHL 957 reported previously is revised here to an upper limit.) The inferred Lyα luminosities lie 1-2 orders of magnitude below estimates of the Lyα luminosities for active star-forming epochs of many prescriptions for galaxy formation and also considerably below measured Lyα luminosities for other candidate young galaxies detected in radio surveys. Under the assumptions that the Lyα luminosity reflects the stellar UV ionizing flux and that the Lyα photons are not destroyed by dust, we set a limiting star-formation rate in these systems of approximately 2-7 M_sun_ yr^-1^. With small but observationally allowable amounts of dust the limit may be about 10 times larger. We suggest that disklike structures form early, within about 1 Gyr of the turnaround epoch, but that rapid star formation does not begin until later epochs, or occurs in episodic fashion. Publication: The Astrophysical Journal Pub Date: December 1989 DOI: 10.1086/168099 Bibcode: 1989ApJ...347...87S Keywords: Cosmology; Emission Spectra; Galactic Evolution; Lyman Alpha Radiation; Quasars; Red Shift; Star Formation; Interstellar Matter; Luminosity; Star Formation Rate; Stellar Evolution; Astrophysics; GALAXIES: EVOLUTION; GALAXIES: FORMATION; GALAXIES: STELLAR CONTENT; STARS: FORMATION full text sources ADS | data products SIMBAD (16) NED (15)

view Abstract Citations (37) References (29) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Formation of Disk Galaxies at High Redshift: Observations of Damped Lyman-Alpha Absorption in High-Redshift QSOs Smith, Harding E. ; Cohen, Ross D. ; Bradley, Steven E. Abstract We present here observations at 3 Å resolution which confirm damped Lyα profiles for a number of candidate galaxy disk absorption systems in a sample of high-redshift QSOs. A combination of strong, self-damped Lyα absorption plus blended narrow absorption features adequately fits the data for 18 systems in 15 objects. This is at least a factor of five in excess of the number of galaxy disks expected to be intercepted by lines of sight to this sample of QSOs. These results imply that approximately 20% of the sky is covered by gaseous disks to a column density, NH I > 2 × 1020 cm-2 in the redshift interval z 2-3. We suggest that gaseous disks form relatively early in galaxies and that they may be considerably larger at early epochs. Publication: The Astrophysical Journal Pub Date: November 1986 DOI: 10.1086/164710 Bibcode: 1986ApJ...310..583S Keywords: Absorption Spectra; Disk Galaxies; Galactic Evolution; Lyman Alpha Radiation; Quasars; Red Shift; Line Spectra; Space Density; Spectrum Analysis; Astrophysics; GALAXIES: FORMATION; LINE PROFILES; QUASARS full text sources ADS | data products NED (27) SIMBAD (15)

view Abstract Citations (51) References (21) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Spectrophotometry of the broad absorption-line QSO PHL 5200. Junkkarinen, V. T. ; Burbidge, E. M. ; Smith, H. E. Abstract Spectrophotometric observations of PHL 5200 conducted from 1974 to 1979 are presented. The semiforbidden C III 1909 and Mg II 2799 emission lines give an emission redshift of 1.981 + or - 0.002 using the peak of the profile. The semiforbidden C III 1909/C IV 1549 emission line ratio, after correction for absorption, is more than the average for normal quasars. In addition, the spectrum shows more structure between C IV 1549 emission and semiforbidden C III 1909 emission than in the case of normal quasars. The absorption profiles are investigated by using symmetrical logarithmic profiles to model the emission lines. The residual intensities at different wavelengths in the absorption troughs are employed to map optical depth as a function of velocity, assuming that the absorption region covers a small part of the sky as seen from the central source. Spectra from five observing seasons are compared, and no apparent changes in the C IV and Si IV absorption troughs are found. Publication: The Astrophysical Journal Pub Date: February 1983 DOI: 10.1086/160653 Bibcode: 1983ApJ...265...51J Keywords: Absorption Spectra; Astronomical Photometry; Emission Spectra; Quasars; Spectral Line Width; Spectrophotometry; Abundance; Astronomical Models; Atomic Spectra; Galactic Structure; Molecular Clouds; Nonequilibrium Ionization; Optical Density; Periodic Variations; Photoionization; Red Shift; Resonance Lines; Spectral Energy Distribution; Astrophysics full text sources ADS | data products SIMBAD (1) NED (1)

view Abstract Citations (13) References (28) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Infrared polarimetry of nine Seyfert galaxies Rudy, R. J. ; Levan, P. D. ; Puetter, R. C. ; Smith, H. E. ; Willner, S. P. Abstract No polarizations greater than 2-3% are detected at a 95% confidence level in measurements of the polarization of nine Seyfert galaxies at 2.3 microns. It is suggested after considering mechanisms that could weaken or modify a strongly polarized nonthermal component that the small polarizations may be explained if the IR fluxes are similar in nature to those of the low-polarization QSOs, although the photometric variability observed in the type 1 Seyfert nuclei contradicts such similarities. It is concluded that the observations are consistent with, but not conclusive evidence of, thermal emission by dust as the source of the near-IR excesses in the present Seyfert galaxies. Publication: The Astrophysical Journal Pub Date: February 1982 DOI: 10.1086/159609 Bibcode: 1982ApJ...253...53R Keywords: Infrared Astronomy; Polarimetry; Seyfert Galaxies; Cosmic Dust; Galactic Nuclei; Spectrophotometry; Astronomy full text sources ADS | data products NED (11)

view Abstract Citations (83) References (48) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Spectrophotometry of faint, red 3C QSO candidates. Smith, H. E. ; Spinrad, H. Abstract Redshifts and spectrophotometry are presented for eight faint QSOs identified with 3C and 3CR radio sources. Seven of these objects are quite red (alpha-opt. not less than 2.5) such that photoionization by the extrapolated nonthermal ultraviolet continuum appears unable to explain the observed emission line spectrum. 3C 93 and 3C 216, previously believed to be BL Lacertae objects, are shown to be relatively strong-lined QSOs with redshifts z = 0.357 and 0.670, respectively Publication: The Astrophysical Journal Pub Date: March 1980 DOI: 10.1086/157758 Bibcode: 1980ApJ...236..419S Keywords: Quasars; Radio Sources (Astronomy); Red Shift; Stellar Spectrophotometry; Emission Spectra; Photoionization; Radio Astronomy; Radio Spectra; Spectral Energy Distribution; Stellar Luminosity; Astronomy full text sources ADS | data products NED (5) Related Materials (1) Erratum: 1980ApJ...240..719S

Spectrophotometric observations of six broad absorption-line QSOs (BALQSOs) are presented. The continua and emission lines are compared with those in the spectra of QSOs without BALs. A statistically significant difference is found in the emission-line intensity ratio for (N V 1240-A)/(C IV 1549-A). The median value of (N V)/(C IV) for the BALQSOs is two to three times the median for QSOs without BALs. The absorption features of the BALQSOs are described, and the column densities and limits on the ionization structure of the BAL region are discussed. If the dominant ionization mechanism is photoionization, then it is likely that either the ionizing spectrum is steep or the abundances are considerably different from solar. Collisional ionization may be a significant factor, but it cannot totally dominate the ionization rate.

view Abstract Citations (13) References (15) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Self-absorption in the Balmer line profiles of the QSO 2141 + 174 /= OX 169/ Smith, H. E. Abstract The QSO 2141 + 174 shows apparent self-absorption in the profiles of the emission lines H-alpha, H-beta and possibly H-gamma. It is suggested that this self-absorption is most readily interpreted as due to a 'broad-line emission cloud' viewed along the line of sight to the continuum source. Under this assumption, the minimum optical depth in H-alpha, Tau0 approx. 40, confirms previous suggestions that QSO broad-line clouds must be optically thick in the Balmer lines and very optically thick in the Lyman lines. It is possible that variations in the column density of absorbing material along the line of sight may account for the X-ray variability of 2141 + 174. Publication: The Astrophysical Journal Pub Date: November 1980 DOI: 10.1086/183377 Bibcode: 1980ApJ...241L.137S Keywords: Astronomical Spectroscopy; Balmer Series; H Lines; Quasars; Self Absorption; Hydrogen Clouds; Line Spectra; Lyman Spectra; X Ray Sources; Astrophysics full text sources ADS |

view Abstract Citations (59) References (32) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS On the abundances in the z = 2.81 absorbing material toward the quasi-stellar object PKS 0528-250. Smith, H. E. ; Jura, M. ; Margon, B. Abstract Results are reported for measurements of line strengths in the z = 2.81 absorption-line system toward the quasar PKS 0528-250. It is found that the L-alpha line probably lies on the damping portion of the curve of growth and that the Al III doublet lines near 1860 A apparently lie on or near the linear portion of the curve of growth. Logarithmic gas-phase abundance ratios (relative to H I) of approximately -7.4 for Al III, -5.9 for S II, and -5.4 for Si II are derived; both sulfur and silicon are shown to be significantly underabundant in comparison with the solar values. It is suggested that the material along the line of sight to PKS 0528-250 is likely to be distributed in several clouds with individual velocity dispersions considerably less than 100 km/s, that the derived abundances probably reflect the total gas-phase abundances of the relevant elements, and that either there is an unusually small dust-to-gas ratio in the absorbing gas or the dust present has different absorption and scattering properties than dust in the Galaxy. The detection of very broad emission lines with a redshift of approximately 2.76 is also discussed. Publication: The Astrophysical Journal Pub Date: March 1979 DOI: 10.1086/156854 Bibcode: 1979ApJ...228..369S Keywords: Absorption Spectra; Abundance; Emission Spectra; Quasars; Atmospheric Diffusion; Cosmic Dust; High Resolution; Line Spectra; Mass Ratios; Red Shift; Astrophysics; Absorption Lines:Quasars; Emission Lines:Quasars; Quasars:Element Abundances full text sources ADS | data products SIMBAD (3) NED (1)

view Abstract Citations (60) References (20) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The nature of the nebulosity associated with the BL Lacertae object AO 0235+164. Smith, H. E. ; Burbidge, E. M. ; Junkkarinen, V. T. Abstract We present photographic and spectrophotometric observations of the faint nebulosity associated with the active BL Lacertae object AO 0235+164. The nebula is centrally concentrated and shows relatively strong emission features which we identify with [0 ii], H , and [0 iii] at z = 0.525, coincident with the lower of the two absorption systems in AO 0235+164. The luminosity in the lines is an order of magnitude greater than that expected for even the most luminous intervening late-type galaxy. Although no definite conclusion can be reached, this and other arguments suggest that the absorption and emission may be produced by material which is physically associated with the BL Lacertae object. Subject headings: BL Lacertae objects nebulae: individual Publication: The Astrophysical Journal Pub Date: December 1977 DOI: 10.1086/155718 Bibcode: 1977ApJ...218..611S Keywords: Astronomical Photometry; Nebulae; Radio Sources (Astronomy); Emission Spectra; H Beta Line; Oxygen Spectra; Spectrophotometry; Astrophysics full text sources ADS | data products NED (1)

view Abstract Citations (184) References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS An optical catalog of quasi-stellar objects. Burbidge, G. R. ; Crowne, A. H. ; Smith, H. E. Abstract A catalog containing the basic optical information on all QSOs which have been certainly identified, meaning that redshifts have been measured (complete to August 1976), is given. Included are the coordinate designations, other names, equatorial coordinates, visual magnitudes, (U-B) and (B-V) colors, emission-line redshifts, emission lines detected in the optical spectrum, absorption-line redshifts, and references for finding charts, absorption- and emission-line redshifts, and photometry and polarimetry for 633 QSOs and four BL Lacertae objects. Cross-reference tables are provided for finding coordinate designations of objects known by noncoordinate names. Publication: The Astrophysical Journal Supplement Series Pub Date: February 1977 DOI: 10.1086/190422 Bibcode: 1977ApJS...33..113B Keywords: Astronomical Catalogs; Optical Properties; Quasars; Red Shift; Absorption Spectra; Emission Spectra; Position (Location); Ubv Spectra; Astronomy full text sources ADS | data products NED (3)

view Abstract Citations (87) References (35) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS On the origin of the absorption spectra of quasi-stellar and BL Lacertae objects. Burbidge, G. ; O'Dell, S. L. ; Roberts, D. H. ; Smith, H. E. Abstract Following the earlier work of Wagoner (1967) we have reexamined the possibility that the absorption spectra of QSOs are due to gas in the disks, coronae, or halos of intervening galaxies. Comparison of the expected number of absorption systems with the number observed in all of the QSOs and BL Lacertae objects so far cataloged shows that there is a gross discrepancy in the sense that the multiplicity of absorption systems already found is far higher than the numbers expected if the absorption is due to gas in known disks or hypothetical small coronae. A discussion of the selection effects suggests that the number of absorption systems so far reported is an underestimate, so that an even greater discrepancy is likely to be present. High multiplicities can be explained only if very large halos or clouds containing heavy elements are commonly present, and there is no independent evidence for this. We conclude that the bulk of the absorption is likely to be intrinsic to the QSOs. Publication: The Astrophysical Journal Pub Date: November 1977 DOI: 10.1086/155654 Bibcode: 1977ApJ...218...33B Keywords: Absorption Spectra; Galactic Structure; Quasars; Variable Stars; Astronomical Spectroscopy; Clouds; Coronas; Halos; Astrophysics full text sources ADS |

view Abstract Citations (24) References (15) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The radio structure and optical field of 3C 303. Kronberg, P. P. ; Burbidge, E. M. ; Smith, H. E. ; Strom, R. G. Abstract New radio and optical observations of the peculiar system 3C 303 are presented. Aperture synthesis maps obtained at 1.4, 2.7, 5.0, and 8.1 GHz show the source to be highly asymmetric double, although it is almost certain that the various radio components are physically related. The two extended outer components have a flux density ratio of about 5:1 at 1.4 GHz. The compact VLBI component has been shown to coincide with a 17th magnitude N galaxy at z = 0.141, while the compact radio core of the extended western component is shown to lie within 1 sec of one member of a trio of faint UV-excess objects. Optical observations of the brightest of the UV-excess objects lying within the western radio component show it to be a QSO with a redshift z = 1.57. Publication: The Astrophysical Journal Pub Date: November 1977 DOI: 10.1086/155652 Bibcode: 1977ApJ...218....8K Keywords: Astronomical Maps; Galactic Radiation; Quasars; Radio Sources (Astronomy); Astronomical Photometry; Calibrating; Polarization Characteristics; Red Shift; Ultraviolet Astronomy; Astronomy full text sources ADS | data products SIMBAD (9)

The galaxy MCG 9-13-66 associated with the large radio source DA 240 has been shown to contain a large jet with a featureless spectrum somewhat bluer in color than the galaxy, oriented at 62degree to the axis of radio emission. Observations made at Kitt Peak National Observatory and Lick Observatory are described.

view Abstract Citations (393) References (52) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Spectrophotometric observations of ionized hydrogen regions in nearby spiral and irregular galaxies. Smith, H. E. Abstract A program of direct photography and spectrophotometry has been carried out on H ii regions in a selection of nearby spiral and irregular galaxies. Abundance analyses for H ii regions in MiOl and M33 show a strong radial gradient in the O!H ratio, decreasing by approximately a factor of 10 across the galaxy disks. The Ne/O and S/O abundance ratios are constant. The derived nitrogen abundances, coupled with the line ratios for other H ii regions, indicate a weak gradient in the ratio of N!O, decreasing by about a factor of 4 from the nuclear regions outward. No large helium abundance differences are observed, although the most oxygen-poor regions may show marginally significant helium deficiencies. Excitation differences among the H ii regions of Sbc-Scd-Irr galaxies can best be understood in terms of an abundance sequence which progresses from higher to lower heavy-element enrichment as one progresses from the earlier to later type galaxies. Subject headings: abundances, nebular - galaxies - nebulae Publication: The Astrophysical Journal Pub Date: August 1975 DOI: 10.1086/153727 Bibcode: 1975ApJ...199..591S Keywords: Astronomical Photometry; Galactic Structure; Hydrogen Clouds; Interstellar Gas; Ionized Gases; Spiral Galaxies; Abundance; Heavy Elements; Line Spectra; Radial Velocity; Spectrophotometry; Astrophysics full text sources ADS | data products NED (50) SIMBAD (21)