QSO-galaxy Pairs Research Articles

Galaxies Probing Galaxies in PRIMUS. II. The Coherence Scale of the Cool Circumgalactic Medium

Abstract The circumgalactic medium (CGM) close to ∼L* star-forming galaxies hosts strong Mg ii λ2796 absorption (with equivalent width W 2796 > 0.1 Å) with a near-unity covering fraction. To characterize the spatial coherence of this absorption, we analyze the W 2796 distribution in the CGM of 27 star-forming galaxies detected in deep spectroscopy of bright background (b/g) galaxies first presented in Rubin et al. The sample foreground (f/g) systems have redshifts and stellar masses 9.1 < log M */M ⊙ < 11.1, and the b/g galaxies provide spatially extended probes with half-light radii at projected distances < 50 kpc. Our analysis also draws on literature W 2796 values measured in b/g QSO spectroscopy probing the halos of f/g galaxies with a similar range in M * at z ∼ 0.25. By making the assumptions that (1) samples of like galaxies exhibit similar circumgalactic W 2796 distributions and, (2) within a given halo, the quantity log W 2796 has a Gaussian distribution with a dispersion that is constant with M * and , we use this QSO–galaxy pair sample to construct a model for the log W 2796 distribution in the CGM of low-redshift galaxies. Adopting this model, we then demonstrate the dependence of the observed log W 2796 distribution on the ratio of the surface area of the b/g probe to the projected absorber surface area (x A ≡ A G/A A), finding that distributions that assume x A ≥ 15 are statistically inconsistent with that observed toward our b/g galaxy sample at a 95% confidence level. This limit, in combination with the b/g galaxy sizes, requires that the length scale over which W 2796 does not vary (i.e., the “coherence scale” of Mg ii absorption) is ℓ A > kpc. This novel constraint on the morphology of cool, photoionized structures in the inner CGM suggests that either these structures each extend over kiloparsec scales or the number and velocity dispersion of these structures are spatially correlated over the same scales.

Galactic nebular lines in the fibre spectra of background QSOs: reaching a hundred QSO–galaxy pairs with spectroscopic and photometric measurements

We present photometric and spectroscopic measurements of 53 QSO-galaxy pairs from the Sloan Digital Sky Survey, where nebular emission lines from a 0<z<0.84 foreground galaxy are detected in the fiber spectra of a background QSO, bringing the overall sample to 103 QSO-galaxy pairs detected in the SDSS. We here study the nature of these systems. Detected foreground galaxies appear at impact parameters between 0.37 kpc and 12.68 kpc. The presence of oxygen and Balmer emission lines allows us to determine the emission line metallicities for our sample, which are on average super-solar in value. Star formation rates for our sample are in the range 0.01-12 M_sol yr^-1. We utilize photometric redshift fitting techniques to estimate the M_stellar values of our galaxies (log M_stellar = 7.34 - 11.54), and extrapolate this relationship to those galaxies with no imaging detections. Where available, we measure the absorption features present in the QSO spectrum due to the foreground galaxy and the relationships between their rest equivalent widths. We report an anti-correlation between impact parameter and E(B-V)_(g-i), as well as a correlation between galaxy color (u-r) and E(B-V)_(g-i). We find that our sample is one of late-type, star forming galaxies comparable to field galaxies in a similar redshift range, providing important clues to better understand absorption systems. These galaxies represent a sample of typical galaxies in the local Universe for which abundances, extinction, morphology, and absorption properties may be measured using background QSOs with great potential for follow-up observations.

Spatially resolved velocity maps of halo gas around two intermediate-redshift galaxies★

Absorption-line spectroscopy of multiply-lensed QSOs near a known foreground galaxy provides a unique opportunity to go beyond the traditional one-dimensional application of QSO probes and establish a crude three-dimensional map of halo gas around the galaxy that records the line-of-sight velocity field at different locations in the gaseous halo. Two intermediate-redshift galaxies are targeted in the field around the quadruply-lensed QSO HE 0435−1223 at redshift z = 1.689, and absorption spectroscopy along each of the lensed QSOs is carried out in the vicinities of these galaxies. One galaxy is a typical, star-forming L* galaxy at z = 0.4188 and projected distance of ρ = 50 kpc from the lensing galaxy. The other is a super-L* barred spiral at z = 0.7818 and ρ = 33 kpc. Combining known orientations of the quadruply-lensed QSO to the two foreground galaxies with the observed Mg ii λλ2796, 2803 absorption profiles along individual QSO sightlines has for the first time led to spatially resolved kinematics of tenuous halo gas on scales of 5–10 kpc at z > 0.2. A Mg ii absorber is detected in every sightline observed through the haloes of the two galaxies, and the recorded absorber strength is typical of what is seen in previous close QSO–galaxy pair studies. While the multisightline study confirms the unity covering fraction of Mg ii absorbing gas at ρ < 50 kpc from star-forming discs, the galaxies also present two contrasting examples of complex halo gas kinematics. Different models, including a rotating disc, collimated outflows and gaseous streams from either accretion or tidal/ram-pressure stripping, are considered for comparisons with the absorption-line observations, and infalling streams/stripped gas of width ≳10 kpc are found to best describe the observed gas kinematics across multiple sightlines. In addition, the observed velocity dispersion between different sightlines offers a crude estimate of turbulence in the Mg ii absorbing halo gas. The observations presented here demonstrate that multiple-QSO probes enable studies of spatially resolved gas kinematics around distant galaxies, which provide key insights into the physical nature of circumgalactic gas beyond the nearby Universe.

Parsec-scale structures and diffuse bands in a translucent interstellar medium at z≃ 0.079★

We present a detailed study of the QSO-galaxy pair [SDSS J163956.35+112758.7 (zq = 0.993) and SDSS J163956.38+112802.1 (zg = 0.079)] based on observations carried out using the Giant Meterwave Radio Telescope (GMRT), the Very Large Baseline Array (VLBA), the Sloan Digital Sky Survey (SDSS) and the ESO New Technology Telescope (NTT). We show that the interstellar medium of the galaxy probed by the QSO line of sight has near-solar metallicity (12+log(O/H) = 8.47+/-0.25) and dust extinction (E(B-V) 0.83+/-0.11) typical of what is usually seen in translucent clouds. We report the detection of absorption in the \lambda 6284 diffuse interstellar band (DIB) with a rest equivalent width of 1.45+/-0.20\AA. Our GMRT spectrum shows a strong 21-cm absorption at the redshift of the galaxy with an integrated optical depth of 15.70+/-0.13 km/s. Follow-up VLBA observations show that the background radio source is resolved into three components with a maximum projected separation of 89 pc at the redshift of the galaxy. One of these components is too weak to provide useful HI 21-cm absorption information. The integrated HI optical depth towards the other two components are higher than that measured in our GMRT spectrum and differ by a factor 2. By comparing the GMRT and VLBA spectra we show the presence of structures in the 21-cm optical depth on parsec scales. We discuss the implications of such structures for the spin-temperature measurements in high-z damped Lyman-alpha systems. The analysis presented here suggests that this QSO-galaxy pair is an ideal target for studying the DIBs and molecular species using future observations in optical and radio wavebands.

Looking at quasars through galaxies

Observations of quasars (QSOs) shining through or close to galaxies offer a way to probe the properties of the foreground matter through dust extinction and gravitational lensing. In this paper the feasibility of measuring the dust extinction properties is investigated using the backlitting of QSOs. We test our method to search for QSOs affected by intervening extinction, by matching the coordinates in the SDSS QSO DR3 catalogue with the New York University Value-Added Galaxy Catalog. In total, 164 QSO-galaxy pairs were found with a distance of less than 30 kpc between the galaxy centre and the QSO line-of-sight at the galaxy redshift. Investigating the QSO colours with multiband SDSS photometry, two pairs with galaxy redshifts z < 0.08 were found to be particularly interesting in that the QSOs show evidence of heavy Galactic type extinction with R_v ~ 3.1 at very large optical radii in the foreground spiral galaxies. With the available data, it remains inconclusive whether the two pairs can be explained as statistical colour outliers, by host extinction or if they provide evidence of dust in the outskirts of spiral galaxies. Deeper galaxy catalogues and/or higher resolution follow-up QSO spectra would help in resolving this problem. We also analyse five QSOs reported in the literature with spectroscopic absorption features originating from an intervening system. These systems are at higher redshifts than the other two and we find in most cases significantly lower best fit values of R_v. The wide range of preferred values of R_v found, although affected by substantial uncertainties, already indicates that the dust properties in other galaxies may be different from the Milky Way. Furthermore, the available data suggests a possible evolution in the dust properties with redshift, with lower R_v at high z.

Critical Examinations of QSO Redshift Periodicities and Associations with Galaxies in Sloan Digital Sky Survey Data

We have used the publicly available data from the Sloan Digital Sky Survey and 2dF QSO redshift survey to test the hypothesis that QSOs are ejected from active galaxies with periodic noncosmological redshifts. For two different intrinsic redshift models, namely the Karlsson log(1 + z) model and Bell's decreasing intrinsic redshift (DIR) model, we do two tests. First, using different criteria, we generate four sets of QSO-galaxy pairs and find there is no evidence for a periodicity at the predicted frequency in log(1 + z), or at any other frequency. We then check the relationship between high-redshift QSOs and nearby active galaxies, and we find that the distribution of projected distance between high-redshift QSOs and nearby active galaxies and the distribution of redshifts of those active galaxies are consistent with a distribution of simulated random pairs, completely different from Bell's previous conclusion. We also analyze the periodicity in redshifts of QSOs, and no periodicity is found in high-completeness samples, contrary to the DIR model. These results support the hypothesis that QSOs are not ejected from active galaxies.

No periodicities in 2dF Redshift Survey data

We have used the publicly available data from the 2dF Galaxy Redshift Survey and the 2dF QSO Redshift Survey to test the hypothesis that there is a periodicity in the redshift distribution of quasi-stellar objects (QSOs) found projected close to foreground galaxies. These data provide by far the largest and most homogeneous sample for such a study, yielding 1647 QSO-galaxy pairs. There is no evidence for a periodicity at the predicted frequency in log(1 + z), or at any other frequency.

Detection of CA II absorption in the QSO 0958 + 559 due to a Heiles shell in NGC 3079

Optical observations of the QSO 0958 + 559 and the nearby, edge-on spiral galaxy NGC 3079 are presented. Spectra of the QSO show Ca II absorption lines due to extended gas in NGC 3079; the Na absorption lines due to NGC 3079 are not detected. An unrelated higher redshift absorption system at 1.1327 is also present in the QSO spectrum. The QSO sightline shines directly through a Heiles shell. The coincidence in position coupled with the agreement between the Ca II absorption and shell emission velocities demonstrates that the QSO absorption system is due to gas in this shell. This system is discussed in comparison with the six other low-redshift QSO-galaxy pair absorption systems, and the influence of Heiles shells on the interpretation of higher redshift QSO absorption systems is addressed.

A survey of interstellar Ca II absorption in the haloes of low-redshift galaxies

Medium-resolution observations of nine QSOs whose lines-of-sight pass within 45 h -1 kpc of low-redshift galaxies are presented. Ca II absorption is detected only for QSO 1543+489. With these data, supplemented by previously published results, the Ca II absorption cross-sections of present-day galaxies are analysed by defining an unbiased sample of QSO-galaxy pair for which all observations have been reported, regardless of the success or otherwise of the search for absorption.

CA II and NA I absorption in the QSO S4 0248 + 430 due to an intervening galaxy

view Abstract Citations (34) References (20) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS CA II and NA I Absorption in the QSO S4 0248+430 due to an Intervening Galaxy Womble, Donna S. ; Junkkarinen, Vesa T. ; Cohen, Ross D. ; Burbidge, E. Margaret Abstract We present observations of the QSO S4 0248 + 430 and a nearby anonymous galaxy taken with the Lick 3m telescope. The proximity of the QSO line of sight to the z = 0.052 galaxy makes it particularly suitable for probing the extent and content of gas in the galaxy. Our moderate resolution spectra of the QSO show two absorption components in both Ca II H and K and Na I D1 and D2 at z_a_ =0.0515, 0.0523. We used a maximum-likelihood Gaussian-fitting technique to measure the equivalent widths of both components in all four lines. Analysis, using best-fit curves of growth, yields column densities of log N(Ca II) = 13.29, 13.50 and log N(Na I) = 13.79, 14.18 (N in units of cm^-2^) for the z_a_=0.0515, 0.0523 absorption systems, respectively. The column density ratios, N( Ca II)/N(Na I) = 0.3, 0.2, indicate considerable calcium depletion and imply disk-type absorbing gas if conditions analogous to the Galaxy exist. Extrapolation of a partial rotation curve of the galaxy to the position of the QSO shows that at least one and possibly both absorption components are produced by high-velocity gas. Additionally, a broadband image of the field shows an asymmetrical armlike feature or possible tidal tail covering and extending past the position of the QSO. The presence of this extended feature and the apparent difference between the absorption velocities and galaxy rotation velocity suggest that the absorbing gas is not ordinary disk gas, but rather is a result of tidal disruption like that seen in the QSO-galaxy pair 1327-206 - ESO 1327-2041. In addition to the low redshift absorption systems, two higher redshift absorption systems are present in the QSO spectrum at z_a_ =0.394 and 0.451. We did not find any galaxies at these absorption redshifts; however, we tentatively identify a galaxy 11 arcsec northeast of the QSO at z = 0.240. Publication: The Astronomical Journal Pub Date: December 1990 DOI: 10.1086/115636 Bibcode: 1990AJ....100.1785W Keywords: Absorption Spectra; Calcium Compounds; Metal Ions; Quasars; Sodium Compounds; Interacting Galaxies; Line Of Sight; Maximum Likelihood Estimates; Red Shift; Astrophysics; QUASARS; GALAXIES: INTERSTELLAR MATTER full text sources ADS | data products SIMBAD (14) NED (6)

Radio Structures in QSO-Galaxy Pairs

It is now generally agreed that if quasars and nearby low redshift galaxies are associated, then there should be luminous connections between them. However, most of the observational evidence being presented is in the optical domain, whereas such evidence should also exist at radio frequencies. We are, therefore, investigating some QSO—Galaxy pairs at radio frequencies to search for luminous connections and other structural peculiarities. Radio maps of some of these sources are presented.

New X-ray and optical observations of the X-ray discovered QSO-galaxy pair 1E 0104.2 + 3153

New X-ray and optical observations are presented of the QSO-galaxy pair 1E 0104.2 + 3153, originally discovered as a serendipitous source in the Einstein Observatory Medium Sensitivity Survey (Gioia et al., 1984). Results from an extremely deep Exosat observation are used to suggest that the QSO rather than the compact group of galaxies is the optical counterpart of the IPC source. High-resolution (1-A) spectroscopy of the broad-absorption-line QSO, which fails to confirm the Ca II H and K absorption features reported by Stocke et al., (1984), is presented and discussed. The presence of broad absorption lines in the QSO spectrum may indicate that intrinsic absorption is the cause of the nondetection of this source in the soft Exosat energy band. Optical monitoring of the QSO over a 2-yr period indicates variability. Possible interpretations of this phenomenon are intrinsic luminosity variation or a cessation of a gravitational lensing effect acting at the time of the Einstein observation.

Spectroscopy of 11 QSO candidates

Eleven QSO candidates have been confirmed from the UKST prism plate of the field 0112-35. Their redshifts, finding charts and the spectra are presented. Among these II QSOs, 6 are in 3 pairs with angular separation less than 4 arcmin; one is in a QSO-galaxy pair.

A high-resolution optical survey of interstellar absorption lines toward globular clusters and extragalactic objects. I - Basic data

view Abstract Citations (38) References (25) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A high-resolution optical survey of interstellar absorption lines toward globular clusters and extragalactic objects. I - Basic data Songaila, A. ; York, D. G. Abstract We present the results of an investigation into the existence of gas in the halo of our own and neighboring galaxies, by means of a study at high resolution of interstellar sodium and calcium lines in the lines of sight to globular cluster cores, individual Magellanic Cloud supergiants, and the nuclei of Seyfert galaxies. A preliminary discussion of the number density of halo components gives a number of 0.5 per 100 kpc above our sensitivity limit, comparable to, but somewhat higher than, is indicated by 21 cm studies of QSO-galaxy pairs. Publication: The Astrophysical Journal Pub Date: December 1980 DOI: 10.1086/158529 Bibcode: 1980ApJ...242..976S Keywords: Absorption Spectra; Calcium; Globular Clusters; Halos; Interstellar Gas; Sodium; Galactic Nuclei; Magellanic Clouds; Quasars; Seyfert Galaxies; Spectrographs; Supergiant Stars; Astronomy full text sources ADS |

Anomalous Redshifts of QSOs

The evidence for association of high redshift QSOs with low redshift galaxies is subject to controversies. If it can be convincingly argued that the observed associations are accidental and could occur with reasonably high probabilities (say &gt; 5%) then the cosmological interpretation of the redshifts of QSOs remains unaffected by the data. If, however, there is increasing evidence, either statistically or in direct physical terms, for these associations to be real, then the excess redshifts of the QSOs become anomalous. Taking the latter alternative seriously, a suggestion was made by Narlikar (Annals of Physics, 107, 325, 1977) that the anomalous redshift of the QSO in a typical QSO-galaxy pair could arise because the particle masses in the QSO were systematically smaller than those in the companion galaxy, as predicted by a theory of gravitation based on Mach's principle. One astrophysical consequence of this effect is that the QSO should appear younger than the galaxy.

Redshifts of southern radio sources. V

view Abstract Citations (36) References (25) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Redshifts of southern radio sources. V. Peterson, B. A. ; Wright, A. E. ; Jauncey, D. L. ; Condon, J. J. Abstract Redshifts derived from further observations with the image-tube dissector scanner on the 4-m Anglo-Australian Telescope are reported for 19 QSOs and three galaxies associated with southern radio sources. Included are the red stellar object PKS 1402 + 044 with a redshift of 3.202, and a QSO-galaxy pair separated by 15 arcsec. Publication: The Astrophysical Journal Pub Date: September 1979 DOI: 10.1086/157299 Bibcode: 1979ApJ...232..400P Keywords: Astronomical Spectroscopy; Quasars; Radio Sources (Astronomy); Red Shift; Astronomical Catalogs; Forbidden Bands; Galactic Radiation; Image Tubes; Line Spectra; Astrophysics; Galaxies:Redshifts; Radio Sources:Redshifts full text sources ADS | data products NED (22) Related Materials (7) Part 1: 1972ApJ...173L..19P Part 2: 1976ApJ...207L...5P Part 3: 1977ApJ...211L.115W Part 4: 1978ApJ...219L...1J Part 5: 1979ApJ...229...73W Part 7: 1984ApJ...286..498J Part 8: 1988ApJ...327..561W

Physical Associations Between Quasi-Stellar Objects and Galaxies

Further evidence is presented relevant to apparent associations between galaxies and quasi-stellar objects. It is shown that for the five 3C QSOs which lie very close to bright galaxies the QSO-galaxy angular separations are inversely proportional to the redshifts of the galaxies. This lends additional support to the association hypothesis. However, an analysis of an essentially disjoint sample of QSOs identified from the Parkes radio catalog, and fainter galaxies in the catalog of Zwicky and his associates, reveals no statistically significant tendency toward pairing of QSOs and galaxies. The results can be explained in one of two ways. One is that, despite the evidence to the contrary, the 3C results are due to chance. The other is that real associations in the second sample are masked by selection effects. It is shown that several selectional biases do indeed discriminate against the detection of QSO-galaxy pairs, especially for fainter objects. Finally, on the assumption that the 3C QSO-galaxy associations are real, the relationship of QSOs to galaxies is discussed.