We report results from a survey of MgII absorbers in the spectra of background QSOs that are within close angular distances to a foreground galaxy at z<0.5, using the Magellan Echellette Spectrograph. We have established a spectroscopic sample of 94 galaxies at a median redshift of <z> = 0.24 in fields around 70 distant background QSOs (z_QSO>0.6), 71 of which are in an 'isolated' environment with no known companions and located at rho <~ 120 h^-1 kpc from the line of sight of a background QSO. The rest-frame absolute B-band magnitudes span a range from M_B-5log h=-16.4 to M_B-5log h=-21.4 and rest-frame B_AB-R_AB colors range from B_AB-R_AB~0 to B_AB-R_AB~1.5. Of these 'isolated' galaxies, we find that 47 have corresponding MgII absorbers in the spectra of background QSOs and rest-frame absorption equivalent width W_r(2796)=0.1-2.34 A, and 24 do not give rise to MgII absorption to sensitive upper limits. Our analysis shows that (1) Wr(2796) declines with increasing distance from 'isolated' galaxies but shows no clear trend in 'group' environments; (2) more luminous galaxies possess more extended MgII absorbing halos with the gaseous radius scaled by B-band luminosity according to R_gas=75x(L_B/L_B*)^(0.35+/-0.03) h^{-1} kpc; (3) there is little dependence between the observed absorber strength and galaxy intrinsic colors; and (4) within R_gas, we find a mean covering fraction of <kappa_0.3>~70% for absorbers of Wr(2796)>=0.3 A and <kappa_0.1>~80% for absorbers of Wr(2796)>=0.1 A. The lack of correlation between Wr(2796) and galaxy colors suggests a lack of physical connection between the origin of extended MgII halos and recent star formation history of the galaxies. Finally, we discuss the total gas mass in galactic halos as traced by MgII absorbers. We also compare our results with previous studies.
We obtained ESI/Keck rotation curves of 10 MgII absorption selected galaxies (0.3 < z < 1.0) for which we have WFPC-2/HST images and high resolution HIRES/Keck and UVES/VLT quasar spectra of the MgII absorption profiles. We perform a kinematic comparison of these galaxies and their associated halo MgII absorption. For all 10 galaxies, the majority of the absorption velocities lie in the range of the observed galaxy rotation velocities. In 7/10 cases, the absorption velocities reside fully to one side of the galaxy systemic velocity and usually align with one arm of the rotation curve. In all c…
We report results from a deep search for redshifted HI 21cm absorption in 55 strong MgII$λ$2796 absorbers (having $W (MgII) > 0.5 Å$) at intermediate redshifts, $0.58 < z_{\rm abs} < 1.70$, with the Green Bank Telescope (GBT) and the Giant Metrewave Radio Telescope (GMRT). Nine detections of HI 21cm absorption were obtained, all at $1.17 < z_{\rm abs} < 1.68$, including three systems reported earlier by Gupta et al. (2007). Absorption was not detected at $> 3σ$ significance in 32 other MgII absorbers, with 26 of these providing strong upper limits to the HI 21cm optical depth, $τ_{3σ} < 0.013$…
We present initial results from the first systematic survey for MgII quasar absorption lines at z > 2.5. Using infrared spectra of 46 high-redshift quasars, we discovered 111 MgII systems over a path covering 1.9 < z < 6.3. Five systems have z > 5, with a maximum of z = 5.33 - the most distant MgII system now known. The comoving MgII line density for weaker systems (Wr < 1.0A) is statistically consistent with no evolution from z = 0.4 to z = 5.5, while that for stronger systems increases three-fold until z \sim 3 before declining again towards higher redshifts. The equivalent width distributio…
We present a catalog of intervening MgII quasar absorption-line systems in the redshift interval 0.36 <= z <= 2.28. The catalog was built from Sloan Digital Sky Survey Data Release Four (SDSS DR4) quasar spectra. Currently, the catalog contains > 17,000 measured MgII doublets. We also present data on the ~44,600 quasar spectra which were searched to construct the catalog, including redshift and magnitude information, continuum-normalized spectra, and corresponding arrays of redshift-dependent minimum rest equivalent widths detectable at our confidence threshold. The catalog is available on the…
We test whether the Tinker & Chen model of MgII absorption due to the gaseous halo around a galaxy can reproduce absorption in quasar pairs (both lensed and physical) and lensed triples and quads from the literature. These quasars exhibit absorption from a total of 38 MgII systems spanning z=0.043 - 2.066 with mean redshift <z>=1.099 and weighted mean rest-frame equivalent width of 0.87 Ang. Using the Tinker & Chen model to generate simulated sight-lines, we marginalize the unknown parameters of the absorbing galaxies: dark matter halo mass, impact parameter, and azimuthal angle on the sky. We…
We investigate the effect of two important, but oft neglected, factors which can affect the detectability of HI 21-cm absorption in MgII absorption systems: The effect of line-of-sight geometry of the coverage of the background radio flux and any possible correlation between the 21-cm line strength and the rest frame equivalent width of the MgII line. Regarding the former, while the observed detection rate at small angular diameter distance ratios is a near certainty, for an unbiased sample, where either a detection or a non-detection are equally likely, at ratios > 0.8 the observed detection …
We present a detailed study of HI and metals for 110 MgII absorption systems discovered at 1.98 <= z <= 5.33 in the infrared spectra of high redshift QSOs. Using new measurements of rest-frame UV lines from optical spectra of the same targets, we compare the high redshift sample with carefully constructed low redshift control samples from the literature to study evolutionary trends from z=0 --> 5.33 (>12 Gyr). We observe a significant strengthening in the characteristic N(HI) for fixed MgII equivalent width as one moves toward higher redshift. Indeed at our sample's mean zbar=3.402, all MgII s…
We present a sample of 68 low-z MgII low-ionization broad absorption-line (loBAL) quasars. The sample is uniformly selected from the SDSS5 according to the following criteria: (1) 0.4<z<0.8, (2) median S/N>7, and (3) MgII absorption-line width > 1600 \kms. The last criterion is a trade-off between the completeness and consistency with respect to the canonical definition of BAL quasars that have the `balnicity index' BI>0 in CIV BAL. We adopted such a criterion to ensure that ~90% of our sample are classical BAL quasars and the completeness is ~80%, based on extensive tests using high-z quasar …
We present a catalogue of MgII absorption systems obtained from high resolution UVES/VLT data of 77 QSOs in the redshift range 0.6 < z < 2.0, and down to an equivalent width W_0 > 0.1 Å. The statistical properties of our sample are found to be in agreement with those from previous work in the literature. However, we point out that the previously observed increase with redshift of dN/dz for weak absorbers, pertains exclusively to very weak absorbers with W_0 < 0.1 Å. Instead, dN/dz for absorbers with W_0 in the range 0.1-0.3 Åactually decreases with redshift, similarly to the case of strong abs…
Sixty percent of gamma-ray bursts (GRBs) reveal strong MgII absorbing systems, which is a factor of ~2 times the rate seen along lines-of-sight to quasars. The discrepancy in the covering factor is most likely to be the result of either quasars being obscured due to dust, or the consequence of many GRBs being strongly gravitationally lensed. We analyze observations of GRBs that show strong foreground MgII absorption. We Monte-Carlo the distances between foreground galaxies in the HUDF and lines of sight distributed randomly within a radius derived from the covering factor, and find that galaxi…
We have directly compared MgII halo gas kinematics to the rotation velocities derived from emission/absorption lines of the associated host galaxies. Our 0.096<z<0.148 volume-limited sample comprises 13 ~L* galaxies, with impact parameters of 12-90 kpc from background quasars sight-lines, associated with 11 MgII absorption systems with MgII equivalent widths 0.3< W_r(2796)<2.3A. For only 5/13 galaxies, the absorption resides to one side of the galaxy systemic velocity and trends to align with one side of the galaxy rotation curve. The remainder have absorption that spans both sides of the gala…
We report 4 new detections of 21-cm absorption from a systematic search of 21-cm absorption in a sample of 17 strong (Wr(MgII 2796)>1A) intervening MgII absorbers at 0.5<z<1.5. We also present 20-cm milliarcsecond scale maps of 40 quasars having 42 intervening strong MgII absorbers for which we have searched for 21-cm absorption. Combining 21-cm absorption measurements for 50 strong MgII systems from our surveys with the measurements from literature, we obtain a sample of 85 strong MgII absorbers at 0.5<z<1 and 1.1<z<1.5. We present detailed analysis of this sample, taking into account the eff…
We use archival UV absorption-line data from HST/STIS to statistically analyse the absorption characteristics of the high-velocity clouds (HVCs) in the Galactic halo towards more than 40 extragalactic background sources. We determine absorption covering fractions of low- and intermediate ions (OI, CII, SiIII, MgII, FeII, SiIII, CIV, and SiIV) in the range fc = 0.20 - 0.70. For detailed analysis we concentrate on SiII absorption components in HVCs, for which we investigate the distribution of column densities, b-values, and radial velocities. Combining information for SiII and MgII, and using a…
The nature of the galaxies that give rise to absorption lines, such as damped Lyman-alpha systems (DLAs) or strong MgII lines, in quasar spectra is difficult to investigate in emission. Taking advantage of the total absorption of the QSO light bluewards of the Lyman limit of two DLAs at z>3.4, we look for the continuum emission from intervening galaxies at z~2 that are identified via strong metal absorption lines. The MgII absorbers have equivalent width large enough to be potential DLA systems. Deep images are obtained with the FOcal Reducer and Spectrograph (FORS1) on the Very Large Telescop…
We study large-scale outflows in a sample of 96 star-forming galaxies at 1<z<2, using near-UV spectroscopy of FeII and MgII absorption and emission. The average blueshift of the FeII interstellar absorption lines with respect to the systemic velocity is -85+/-10 km/s at z~1.5, with standard deviation 87 km/s; this is a decrease of a factor of two from the average blueshift measured for far-UV interstellar absorption lines in similarly selected galaxies at z~2. The profiles of the MgII 2796, 2803 lines show much more variety than the FeII profiles, which are always seen in absorption; MgII rang…
(Abridged) Star formation-driven outflows are a critical phenomenon in theoretical treatments of galaxy evolution, despite the limited ability of observations to trace them across cosmological timescales. If the strongest MgII absorption-line systems detected in the spectra of background quasars arise in such outflows, "ultra-strong" MgII (USMgII) absorbers would identify significant numbers of galactic winds over a huge baseline in cosmic time, in a manner independent of the luminous properties of the galaxy. To this end, we present the first detailed imaging and spectroscopic study of the fi…
We measure the large-scale clustering of MgII λλ2796,2803 absorbers with respect to a population of luminous red galaxies (LRGs) at z \sim 0.5. From the cross-correlation measurements between MgII absorbers and LRGs, we calculate the mean bias of the dark matter halos in which the absorbers reside. We investigate systematic uncertainties in the clustering measurements due to the sample selection of LRGs and due to uncertainties in photometric redshifts. First, we compare the cross-correlation amplitudes determined using a it flux-limited LRG sample and a volume-limited one. The comparison show…
We present the results of a spectroscopic survey of galaxies in the vicinity of an ultra-strong MgII λλ2786,2803 absorber of rest-frame absorption equivalent width W_r(2796)=4.2Å at z=0.5624. This absorber was originally found at projected separation ρ=246 kpc of a luminous red galaxy (LRG) at z=0.5604. Magellan IMACs spectroscopy has revealed two galaxies at ρ< 60 kpc (z=0.5623 and z=0.5621) and a third one at ρ=209 kpc (z=0.5623) near the redshift of the absorber.These findings indicate that the absorbing gas resides in a group environment. Combining SDSS broadband photometry with additional…
Based on recent results on the frequency of MgII absorption line systems in the "QSO behind RCS clusters" survey (QbC), we analyse the effects of the cluster environment on the sizes of baryonic haloes around galaxies. We use two independent models, i) an empirical halo occupation model which fits current measurements of the clustering and luminosity function of galaxies at low and high redshifts, and ii) the GALFORM semi-analytic model of galaxy formation, which follows the evolution of the galaxy population from first principles, adjusted to match the statistics of low and high redshift gala…
We present HST-COS spectra of ten quasars located behind M31, selected to investigate the properties of gas associated with its extended disk and high velocity clouds (HVCs). The sightlines have impact parameters ranging between b= 13 kpc and 112 kpc. No absorption is detected in the four sightlines beyond b=57 kpc. Of the six remaining sightlines, all of which lie at b<32 kpc and within the N(HI)= 2E18 cm^{-2} boundary of the HI disk of M31, we detect low-ionization absorption at M31 velocities along four of them (three of which include MgII absorption). We also detect MgII absorption from an…
We present a measurement of the cross-correlation of MgII absorption and massive galaxies, using the DR11 main galaxy sample of the Baryon Oscillation Spectroscopic Survey of SDSS-III (CMASS galaxies), and the DR7 quasar spectra of SDSS-II. The cross-correlation is measured by stacking quasar absorption spectra shifted to the redshift of galaxies that are within a certain impact parameter bin of the quasar, after dividing by a quasar continuum model. This results in an average MgII equivalent width as a function of impact parameter from a galaxy, ranging from 50 kpc to more than 10 Mpc in prop…
We study the connections between on-going star formation, galaxy mass, and extended halo gas, in order to distinguish between starburst-driven outflows and infalling clouds that produce the majority of observed MgII absorbers at large galactic radii (>~ 10 h^{-1} kpc) and to gain insights into halo gas contents around galaxies. We present new measurements of total stellar mass (M_star), H-alpha emission line strength (EW(H-alpha)), and specific star formation rate (sSFR) for the 94 galaxies published in H.-W. Chen et al. (2010). We find that the extent of MgII absorbing gas, R_MgII, scales wit…
We report the first comparative study of strong MgII absorbers seen towards radio-loud quasars of core-dominated (CDQs) and lobe-dominated (LDQs) types and normal QSOs. The MgII associated absorption systems having a velocity offset v < 5000km/s from the systemic velocity of the background quasar were also excluded. Existing spectroscopic data for redshift-matched sightlines of 3975 CDQs and 1583 LDQs, covering a emission redshift range 0.39-4.87, were analysed and 864 strong MgII absorbers were found, covering the redshift range 0.45-2.17. The conclusions reached using this well-defined large…
We report a bimodality in the azimuthal angle distribution of gas around galaxies as traced by MgII absorption: Halo gas prefers to exist near the projected galaxy major and minor axes. The bimodality is demonstrated by computing the mean azimuthal angle probability distribution function using 88 spectroscopically confirmed MgII absorption-selected galaxies [W_r(2796)>0.1A] and 35 spectroscopically confirmed non-absorbing galaxies [W_r(2796)<0.1A] imaged with HST and SDSS. The azimuthal angle distribution for non-absorbers is flat, indicating no azimuthal preference for gas characterized by W_…
We present final statistics from a survey for intervening MgII absorption towards 100 quasars with emission redshifts between $z=3.55$ and $z=7.08$. Using infrared spectra from Magellan/FIRE, we detect 279 cosmological MgII absorbers, and confirm that the incidence rate of $W_r>0.3 Å$ MgII absorption per comoving path length does not evolve measurably between $z=0.25$ and $z=7$. This is consistent with our detection of seven new MgII systems at $z>6$, a redshift range that was not covered in prior searches. Restricting to relatively strong MgII systems ($W_r>1$Å), there is significant evidence…
We present joint constraints on the distribution of MgII absorption around galaxies, by combining the MgII absorption seen in stacked background galaxy spectra and the distribution of host galaxies of strong MgII systems from the spectra of background quasars. We present a suite of models that predict, the dependence of MgII absorption on a galaxy's apparent inclination, impact parameter(b) and azimuthal angle. The variations in the absorption strength with azimuthal angles provide much stronger constraints on the intrinsic geometry of the MgII absorption than the dependence on the galaxy's in…
We use a halo occupation approach to connect MgII absorbers to dark matter halos as a function of redshift. Using the model constructed in Tinker & Chen (2008), we parameterize the conditional probability of an absorber of equivalent width Wr being produced by a halo of mass M_h at a given redshift, P(Wr|M_h,z). We constrain the free parameters of the model by matching the observed statistics of MgII absorbers: the frequency function f(Wr), the redshift evolution n(z), and the clustering bias b(Wr). The redshift evolution of Wr>1 A absorbers increases from z=0.4 to z=2, while the total halo cr…
It is well established that MgII absorption lines detected in background quasar spectra arise from gas structures associated with foreground galaxies. The degree to which galaxy evolution is driven by the gas cycling through halos is highly uncertain because their gas mass density is poorly constrained. Fitting the MgII equivalent width (W) distribution with a Schechter function and applying the N(HI)-W correlation of Menard & Chelouche, we computed Omega(HI)_MgII ~ Omega(HI)_halo =(1.41 +0.75 -0.44)x10^-4 for 0.4<z<1.4. We exclude DLAs from our calculations so that Omega(HI)_halo comprises ac…
We investigate the dependence of residual rotation measure (RRM) on intervening absorption systems at cosmic distances by using a large sample of 539 SDSS quasars in conjunction with the available rotation measure catalog at around 21cm wavelength. We found an excess extragalactic contribution in standard deviation of observed RRM of about 8.11+/-4.83 Rad/m^2 in our sample with intervening MgII absorber as compare to the sample without MgII absorber. Our results suggest that intervening absorbers could contribute to the enhancement of RRM at around 21cm wavelength, as was found earlier for RM …
We present an empirical connection between cold gas in galactic halos and star formation. Using a sample of more than 8,500 MgII absorbers from SDSS quasar spectra, we report the detection of a 15 sigma correlation between the rest equivalent width W0 of MgII absorbers and the associated OII luminosity, an estimator of star formation rate. This correlation has interesting implications: using only observable quantities we show that MgII absorbers trace a substantial fraction of the global OII luminosity density and recover the overall star formation history of the Universe derived from classica…
We report the first measurements of MgII absorption systems associated with spectroscopically confirmed z~0.1 star-forming galaxies at projected distances of D<6kpc. We demonstrate the data are consistent with the well known anti-correlation between rest-frame MgII equivalent width, Wr(2796), and impact parameter, D, represented by a single log-linear relation derived by Nielsen et al. (MAGIICAT) that converges to ~2A at D=0kpc. Incorporating MAGIICAT, we find that the halo gas covering fraction is unity below D~25kpc. We also report that our D<6kpc absorbers are consistent with the Wr(2796) d…
We explore the distribution of cool (~$10^4$K) gas around galaxies and its dependence on galaxy properties. By cross-correlating about 50,000 MgII absorbers with millions of sources from the SDSS (optical), WISE (IR), and GALEX (UV) surveys we effectively extract about 2,000 galaxy-absorber pairs at z~0.5 and probe relations between absorption strength and galaxy type, impact parameter and azimuthal angle. We find that cool gas traced by MgII absorbers exists around both star-forming and passive galaxies with a similar incidence rate on scales greater than 100 kpc but each galaxy type exhibits…
The XQ-100 survey provides optical and near infrared coverage of 36 blindly selected, intervening damped Lyman alpha systems (DLAs) at 2 < z < 4, simultaneously covering the MgII doublet at 2796A, 2803A, and the Ly-alpha transition. Using the XQ-100 DLA sample, we investigate the completeness of selecting DLA absorbers based on their MgII rest-frame equivalent width (W2796) at these redshifts. Of the 29 DLAs with clean MgII profiles, we find that six (20% of DLAs) have W2796 < 0.6A. The DLA incidence rate of W2796 < 0.6A absorbers is a factor of ~5 higher than what is seen in z~1 samples, indi…
We describe a search for MgII(2796,2803) absorption lines in Sloan Digital Sky Survey (SDSS) spectra of QSOs whose lines of sight pass within impact parameters of 200 kpc of galaxies with photometric redshifts of z=0.46-0.6 and redshift errors Delta z~0.05. The galaxies selected have the same colors and luminosities as the Luminous Red Galaxy (LRG) population previously selected from the SDSS. A search for Mg II lines within a redshift interval of +/-0.1 of a galaxy's photometric redshift shows that absorption by these galaxies is rare: the covering fraction is ~ 10-15% between 20 and 100 kpc,…
We present the results of a systematic Giant Metrewave Radio Telescope (GMRT) survey of 21-cm absorption in a representative and unbiased sample of 35 strong MgII systems in the redshift range: zabs~1.10-1.45, 33 of which have W_r>1 Å. The survey using ~400hrs of telescope time has resulted in 9 new 21-cm detections and stringent 21-cm optical depth upper limits (median 3-sigma optical depth per 10 km/s of 0.017) for the remaining 26 systems. This is by far the largest number of 21-cm detections from any single survey of intervening absorbers. Prior to our survey no intervening 21-cm system wa…
We report a correlation between velocity offset (beta = v/c) of strong Mg II absorption systems and the bolometric luminosity (L_bol) of quasars in SDSS-DR7. We find that, beta shows a power law increase with L_bol, with a slope (~ 1/4). We find that such a relation of beta with L_bol is expected for outflows driven by scattering of black hole radiation by dust grains, and which are launched from the innermost dust survival radius. Our results indicate that a significant fraction of the strong MgII absorbers, in the range of beta = (0--0.4) may be associated with the quasars themselves.
We have used GIM2D to quantify the morphological properties of 40 intermediate redshift MgII absorption-selected galaxies (0.03<Wr(2796)<2.9 Ang), imaged with WFPC-2/HST, and compared them to the halo gas properties measured form HIRES/Keck and UVES/VLT quasar spectra. We find that as the quasar-galaxy separation, D, increases the MgII equivalent decreases with large scatter, implying that D is not the only physical parameter affecting the distribution and quantity of halo gas. Our main result shows that inclination correlates with MgII absorption properties after normalizing out the relations…
We present the first results of an ongoing spectroscopic follow-up of close luminous red galaxy (LRGs) and MgII λλ 2796,2803 absorber pairs for an initial sample of 15 photometrically selected LRGs at physical projected separations ρ \le 350 kpc/h from a QSO sightline. Our moderate-resolution spectra confirm a physical association between the cool gas (T ~ 1e4 K) revealed by the presence of MgII absorption features and the LRG halo in five cases. In addition, we report an empirical estimate of the maximum covering fraction (κ_max) of cool gas in massive, \ge 1e13 Msun/h dark matter halos hosti…
We have identified 469 MgII doublet systems having W_r >= 0.02 Å in 252 Keck/HIRES and UVES/VLT quasar spectra over the redshift range 0.1 < z < 2.6. Using the largest sample yet of 188 weak MgII systems (0.02 Å <= W_r < 0.3 Å), we calculate their absorber redshift path density, dN/dz. We find clear evidence of evolution, with dN/dz peaking at z ~ 1.2, and that the product of the absorber number density and cross section decreases linearly with increasing redshift; weak MgII absorbers seem to vanish above z ~ 2.7. If the absorbers are ionized by the UV background, we estimate number densities …
We present a spectroscopic sample of z \approx 0.5 luminous red galaxies (LRGs) that are located within physical projected distances ρ\leq 350 kpc/h of a QSO sightline. Of the 37 LRGs in our sample, eight have associated MgII absorbers with rest-frame equivalent width Wr(2796)>0.3A and velocity separation |dv| \leq 350 km/s and 29 do not have associated MgII absorbers to a 2-sigma limit of Wr(2796)=0.3A. We perform a stellar population synthesis analysis using stacked spectra of the MgII absorbing and non-absorbing LRG subsamples. We find that LRGs with or without associated MgII absorbers sha…
This paper investigates the effect of differential aperture loss with SDSS fibers and examines whether such selection bias would result in the observed correlation between rest-frame absorption equivalent width of MgII absorbers, Wr(2796), and mean associated [OII] luminosity, L_[OII], in SDSS QSO spectra. We demonstrate based on a Monte Carlo simulation that the observed Wr(2796) vs. L_[OII] correlation of MgII absorbers can be well-reproduced, if all galaxies found in deep surveys possess extended MgII halos and if the extent of MgII halos scales proportionally with galaxy mass as shown in p…
We present a study of the evolution of several classes of MgII absorbers, and their corresponding FeII absorption, over a large fraction of cosmic history: 2.3 to 8.7 Gyrs from the Big Bang. Our sample consists of 87 strong (Wr(MgII)>0.3 A) MgII absorbers, with redshifts 0.2<z<2.5, measured in 81 quasar spectra obtained from the Very Large Telescope(VLT)/Ultraviolet and Visual Echelle Spectrograph(UVES) archives of high-resolution spectra (R \sim 45,000). No evolutionary trend in Wr(FeII)/Wr(MgII) is found for moderately strong MgII absorbers (0.3<Wr(MgII)<1.0 A). However, at lower z we find a…
We investigate the extent and the properties of the MgII cool, low-density absorbing gas located in the halo and in the circum-galactic environment of quasars, using a sample of 31 projected quasar pairs with impact parameter pd<200kpc in the redshift range 0.5<z<1.6. In the transverse direction, we detect 18 MgII absorbers associated with the foreground quasars, while no absorption system originated by the gas surrounding the quasar itself is found along the line-of-sight. This suggests that the quasar emission induces an anisotropy in the absorbing gas distribution. Our observations indicate…
Background quasars are potentially sensitive probes of galactic outflows provided that one can determine the origin of the absorbing material since both gaseous disks and strong bipolar outflows can contribute to the absorption cross-section. Using a dozen quasars passing near spectroscopically identified galaxies at $z\sim0.1$, we find that the azimuthal orientation of the quasar sight-lines with strong MgII absorption (with EW>0.3 Å) is bi-modal: about half the MgII sight-lines are aligned with the major axis and the other half are within 30deg. of the minor axis, showing that bipolar outflo…
We present optical spectroscopy of projected QSO pairs to investigate the MgII and the CIV absorption features imprinted on the spectrum of the background object by the gaseous halo surrounding the foreground QSO. We observed 13 projected pairs in the redshift range 0.7<z<2.2 spanning projected separations between 60 kpc and 120 kpc. In the spectra of the background QSOs, we identify MgII intervening absorption systems associated to the foreground QSOs in 7 out of 10 pairs, and 1 absorption system out of 3 is found for CIV. The distribution of the equivalent width as a function of the impact p…
We present a sample of 46 [OIII]-emitting galaxies at z<0.8 detected in the fibre spectra of quasars from the SDSS-DR7 through an automatic search procedure. We also detect [OII] and Hb emission lines from most of these galaxies in the SDSS spectra. We study both the emission and absorption properties of a sub-sample of 17 galaxies in the redshift range z=0.4-0.7, where MgII lines are covered by the SDSS spectra. The measured lower-limits on the star-formation rates of these galaxies are in the range 0.2-20 M_sun/yr. The emission line luminosities and (O/H) metallicities from R23 measured in t…
A few percent of quasars show strong associated MgII absorption, with velocities (v_off) lying within a few thousand km/s from the quasar systemic redshift. These associated absorption line systems (AALs) are usually interpreted as absorbers that are either intrinsic to the quasar and its host, or arising from external galaxies clustering around the quasar. Using composite spectra of ~1,800 MgII AAL quasars selected from SDSS DR7 at 0.4<~ z<~2, we show that quasars with AALs with v_off<1500 km/s have a prominent excess in [OII]3727 emission (detected at >7sigma) at rest to the quasar host, com…
We describe the MgII Absorber-Galaxy Catalog, MAGIICAT, a compilation of 182 spectroscopically identified intermediate redshift (0.07 < z < 1.1) galaxies with measurements of MgII 2796, 2803 absorption from their circumgalactic medium within projected distances of 200 kpc from background quasars. In this work, we present "isolated" galaxies, which are defined as having no spectroscopically identified galaxy within a projected distance of 100 kpc and a line of sight velocity separation of 500 km/s. We standardized all galaxy properties to the Lambda CDM cosmology and galaxy luminosities, absolu…
We present a study of metal-enriched halo gas traced by MgII and CIV absorption at z<2 in the MUSE Analysis of Gas around Galaxies survey and the Quasar Sightline and Galaxy Evolution survey. Using these large and complete galaxy surveys in quasar fields, we study the dependence of the metal distribution on galaxy properties and overdensities, out to physical projected separations of 750 kpc. We find that the cool, low-ionization gas is significantly affected by the environment across the full redshift range probed, with ~2-3 times more prevalent and stronger MgII absorption in higher overdens…
Strong foreground absorption features from singly-ionized Magnesium (Mg II) are commonly observed in the spectra of quasars and are presumed to probe a wide range of galactic environments. To date, measurements of the average dark matter halo masses of intervening Mg II absorbers by way of large-scale cross-correlations with luminous galaxies have been limited to z<0.7. In this work we cross-correlate 21 strong (Wλ2796>0.6 °A) Mg II absorption systems detected in quasar spectra from the Sloan Digital Sky Survey Data Release 7 with ~32,000 spectroscopically confirmed galaxies at 0.7<z<1.45 from…
The kinematics of MgII absorbers is the key to understanding the origin of cool, metal-enriched gas clouds in the circumgalactic medium of massive quiescent galaxies. Exploiting the fact that the cloud line-of-sight velocity distribution is the only unknown for predicting the redshift-space distortion~(RSD) of MgII absorbers from their 3D real-space distribution around galaxies, we develop a novel method to infer the cool cloud kinematics from the redshift-space galaxy-cloud cross-correlation $ξ^{s}$. We measure $ξ^{s}$ for ${\sim}10^4$ MgII absorbers around ${\sim}8{\times}10^5$ CMASS galaxie…
(Abridged) Under the hypothesis that MgII absorbers found near the minor axis of a galaxy originate in the cool phase of winds, we carry out a study to constrain the properties of large-scale outflows at redshift z >= 0.5 based on the observed relative motions of individual absorbing clouds with respect to the positions and orientations of the galaxies. We identify in the literature four highly inclined disk galaxies located within 50 kpc and with the minor axis oriented within 45 degrees of a background QSO sightline. Deep HST images of the galaxies are available for accurate morphologies of …
We study the kinematically narrow, low-ionization line emission from a bright, starburst galaxy at z = 0.69 using slit spectroscopy obtained with Keck/LRIS. The spectrum reveals strong absorption in MgII and FeII resonance transitions with Doppler shifts of -200 to -300 km/s, indicating a cool gas outflow. Emission in MgII near and redward of systemic velocity, in concert with the observed absorption, yields a P Cygni-like line profile similar to those observed in the Ly alpha transition in Lyman Break Galaxies. Further, the MgII emission is spatially resolved, and extends significantly beyond…
We argue that most strong intervening metal absorption line systems, where the rest equivalent width of the MgII 2796A line is >0.5A, are interstellar material in, and outflowing from, star-forming disks. We show that a version of the Kennicutt-Schmidt law is readily obtained if the MgII equivalent widths are interpreted as kinematic broadening from absorbing gas in outflowing winds originating from star-forming galaxies. Taking a phenomenological approach and using a set of observational constraints available for star-forming galaxies, we are able to account for the density distribution of st…
MgII absorbers induce reddening on background quasars. We measure this effect and infer the cosmic density of dust residing in these systems to be Ω ~ 2e-6, in units of the critical density of the Universe, which is comparable to the amount of dust found in galactic disks or about half the amount inferred to exist outside galaxies. We also estimate the neutral hydrogen abundance in MgII clouds to be Ω ~ 1.5e-4, which is approximately 5% of hydrogen in stars in galaxies. This implies a dust-to-gas mass ratio for MgII clouds of about 1/100, which is similar to the value for normal galaxies. This…
We present the cross-correlation function of MgII absorbers with respect to a volume-limited sample of luminous red galaxies (LRGs) at z=0.45-0.60 using the largest MgII absorber sample and a new LRG sample from SDSS DR7. We present the clustering signal of absorbers on projected scales r_p = 0.3-35 Mpc/h in four Wr(2796) bins spanning Wr(2796)=0.4-5.6A. We found that on average MgII absorbers reside in halos < log M_h > \approx 12.1, similar to the halo mass of an L_* galaxy. We report that the weakest absorbers in our sample with W_r(2796)=0.4-1.1A reside in relatively massive halos with < l…
We examine the MgII absorbing circumgalactic medium (CGM) for the 182 intermediate redshift (0.072 < z < 1.120) galaxies in the "MgII Absorber-Galaxy Catalog" (MAGIICAT, Nielsen et al.). We parameterize the anti-correlation between equivalent width, Wr(2796), and impact parameter, D, with a log-linear fit, and show that a power law poorly describes the data. We find that higher luminosity galaxies have larger Wr(2796) at larger D (4.3 sigma). The covering fractions, f_c, decrease with increasing D and Wr(2796) detection threshold. Higher luminosity galaxies have larger f_c; no absorption is de…
In 2006, Prochter et al. reported a statistically significant enhancement of very strong Mg II absorption systems intervening the sightlines to gamma-ray bursts (GRBs) relative to the in- cidence of such absorption along quasar sightlines. This counterintuitive result, has inspired a diverse set of astrophysical explanations (e.g. dust, gravitational lensing) but none of these has obviously resolved the puzzle. Using the largest set of GRB afterglow spectra available, we reexamine the purported enhancement. In an independent sample of GRB spectra with a survey path 3 times larger than Prochter…
