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Illustrative image of the two lines-of-sight (LOS) to the QSOs LBQS 0107-025A and B. The region shown is 7.1’ × 6.2’, with North up and East to the left. The two QSOs discussed in this paper are labelled, as is a third QSO (labelled C) to the North (Young et al. 2001). A few of the measured galaxy redshifts in the field are labelled (drawn so the decimal point is approximately above the relevant galaxy) and the projected spatial offset and velocity difference to detected absorbers in either of the LOS are marked for two example galaxies. See the text for a discussion. The image shown was made from a 90 second exposure without a filter using the Palomar Observatory 5m telescope and COSMIC imager/multi-object spectrograph on September 22, 1995UT.
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We investigate the relative distribution of the gaseous contents of the Universe (as traced by a sample of Lyman alpha (lya) absorbers), and the luminous baryonic matter (as traced by a redshift survey of galaxies in the same volume searched for lya absorbers), along 16 lines-of-sight (LOS) between redshifts 0 and 1. Our galaxy redshift survey was...
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... zero (i.e. when the universe was approximately 5% of its current age, to the present day). In this paper we investigate this process observationally during the second half of the evolution of the universe. There is a continuing debate about the relationship between low redshift Lyman α (Ly- α ) absorbers and galaxies, where here ‘low redshift’ is taken to mean redshifts less than 1. A simplified (strawman) version of the two sides is (a) that all low redshift Ly- α absorbers are part of physically- distinct luminous-galaxy halos, or (b) that they are all part of the filamentary structure seen in recent SPH/Mesh structure formation models, and are only related to galaxies by the fact that both are following the underlying dark matter distribution. In practice, almost all authors acknowledge that the universe includes a mix of the above two populations (and indeed others), and the debate is more about which population dominates a particular set of observations. Both of these positions have been vigorously defended in the literature. The reference list below includes all relevant papers listed on the ADS abstract server from the time of the first available high quality UV spectroscopy from HST to 15 August 2005. Papers supporting (a) include (in chronological order): Mo (1994); Lanzetta et al. (1995); Lanzetta et al. (1996); Barcons et al. (1998); Linder (1998); Chen et al. (1998); Ortiz-Gil et al. (1999); Linder (2000); Chen et al. (2001); Chen et al. (2001); Steidel et al. (2002); Charlton et al. (2003); Zonak et al. (2004); Stocke et al. (2004); Bouché et al. (2004); Dahlem (2005); Tumlinson et al. (2005); Keeney et al. (2005); Masiero et al. (2005) and Jenkins et al. (2005). Papers supporting (b) include (in chronological order): Morris et al. (1991); Morris et al. (1993); Morris & van den Bergh (1994); Mo & Morris (1994); Weymann et al. (1995); Dinshaw et al. (1995); Stocke et al. (1995); Shull et al. (1996); Bahcall et al. (1996); Rauch et al. (1996); Le Brun et al. (1996); Bowen et al. (1996); van Gorkom et al. (1996); Dinshaw et al. (1997); Jannuzi et al. (1998); Grogin & Geller (1998); Weymann et al. (1998); Tripp et al. (1998); vanden Berk et al. (1999); Impey et al. (1999); Penton et al. (2000); Penton et al. (2000); Penton et al. (2002); Tripp et al. (2002); Tripp et al. (2002); McLin et al. (2002); Manning (2002); McLin et al. (2002); Bowen et al. (2002); Rosenberg et al. (2003); Manning (2003); Penton et al. (2004); Bregman et al. (2004); Sembach et al. (2004); C oté et al. (2005); Danforth & Shull (2005) and Chen et al. (2005). Finally to complete the reference list, some of the theoretical papers from the last ten years which are relevant for this debate are: Hernquist et al. (1996); Zhang et al. (1997); Cen et al. (1998); Theuns et al. (1998); Davé et al. (1999); Cen & Ostriker (1999); Davé & Tripp (2001); Schaye (2001); McDonald et al. (2002); Scannapieco et al. (2002); Viel et al. (2002); Theuns et al. (2002); McDonald et al. (2002); Nagamine et al. (2004a); Nagamine et al. (2004b); Fujita et al. (2004); Aguirre et al. (2005); Tumlinson & Fang (2005); Scannapieco (2005); Furlanetto et al. (2005); Viel et al. (2005) and Jena et al. (2005). Regardless of whether either hypothesis is correct, we emphasize that even if one (naively) believes a clear answer can be obtained (either (a) or (b) above), this answer will be a function of the neutral Hydrogen column density of the absorbers. For N H I > 10 21 cm − 2 , one is probing a column density of material comparable to that of the disk of our galaxy, and hence all galaxies, to varying degrees, should be expected to contribute to the population of such absorbers. At column densities N H I ∼ 10 12 cm − 2 , one is getting close to the neutral hydrogen content of the expected fluctuations within voids, and we expect that a more heterogeneous set of causes could produce such absorption. The increasingly sophisticated models of galaxy formation and evolution now available (see references above) suggest that if we could make a perfect census of the gaseous and luminous constituents of a large volume of the low redshift Universe, we would find that both the gas (quasar absorption line systems) and stars (galaxies) trace the same fundamental structures (whose course of formation and distribution was set by the early perturbations of the distribution of dark matter in the Universe). These same models, however, also indicate that a wide range of detailed relationships between the gas and galaxies should be observed. The details of the structures will depend on an equally wide range of interesting astrophysics, including the process of star formation and “galaxy feedback” and we hope that the approach of this paper can lead to a better understanding of this astrophysics. Observationally comparing the distribution of galaxies and quasar absorption line systems shows some of the com- plexity of the phenomena at work. This can be illustrated by considering Figure 1. In this figure we show an image of the lines-of-sight (LOS) towards the QSOs LBQS 0107-025A and B. As discussed later in the paper, for this field we have samples of galaxies and Ly- α absorption line systems whose locations in this common volume of space can be compared. In the figure we have selectively labelled illustrative cases of ‘associated’ galaxies and absorption lines. For two of the galaxies labelled with a redshift, arrows indicate where there is a detected absorption line in both of the QSO spectra. For those absorber-galaxy pairs, the projected spatial separation and velocity difference between the galaxy and the absorber are also provided. We consider a few of these cases below: (i) A bright, multi-component object lies between the two QSOs at a redshift of 0.2272. There is absorbing gas seen at nearly this same redshift in both QSO LOS, and in one of them, CIV absorption is also detected. This then could potentially be interpreted as a straightforward case of a large gaseous halo around a bright galaxy. The complex morphol- ogy of the galaxy could indicate an ongoing merger. (ii) At a distance of 350 kpc to the south and east of the two QSO LOS is another bright morphologically-complex galaxy at a redshift of 0.1145. This galaxy is also close in velocity to absorption seen in both LOS. It is instructive though to compare the small visible extent of the stars in the (large) galaxy with the distance to the two QSO LOS. Smooth, undisturbed gaseous halos of this size seem im- probable, although it is one of the goals of this paper to investigate this statistically. (iii) Generally to the north of the two QSOs are a collection of 5 galaxies marked with redshifts near 0.20. All 5 of these galaxies are within 500 km s − 1 (and also within a projected distance of 500 kpc) of an absorber seen in the LOS to LBQS 0107-025B. No absorption is detected in the other QSO LOS. This collection illustrates the common difficulty of picking out one individual galaxy to tie to one absorber. Although there is indeed a single ‘closest’ galaxy, it seems rather arbitrary to claim that it is the sole cause of any absorption. (iv) Finally, a collection of six galaxies, all within 500 km s − 1 of each other at a redshift around 0.24 are marked sur- rounding the LOS to LBQS 0107-025A. Despite their prox- imity to the LOS, and the case above where a group of galaxies can be associated with an absorber, no absorption is seen at this redshift in either of the two QSO LOS. While one could speculate that low column density absorbers might be fragile entities that are destroyed in a dense environment, there is no good independent evidence at present that this galaxy ‘group’ has crossed such a threshold. These examples demonstrate the great variety of ap- pearances the underlying relationship between the absorbers and galaxies presents, along even one LOS. This richness should be kept in mind when interpreting the results derived from the ensemble of data we consider in this paper. The outline of the paper is as follows: in § 2 we describe the various data sets used in this paper. In § 3 we analyse the data, and in § 4 we present our conclusions. Our observational program would ideally be designed to allow a statistical comparison between the absorption gas detected in Hubble Space Telescope (HST) UV spectroscopy between redshifts of 0 and 1 and the galaxies within a 1 cylindrical region at least 3 Mpc in radial extent away from the QSO Line of Sight (LOS). In practice, what we achieved was an absorption line sample taken from the HST Quasar Absorption Line Survey (Bahcall et al. 1993, 1996; Jannuzi et al. 1998), an HST Key Project during cycles 1-4, with varying redshift coverage, and galaxy samples from a variety of observatories. The main one reported here was obtained using the Multi-Object Spectrograph (MOS) at the Canada-France-Hawaii Telescope (CFHT). Some additional galaxy redshifts have been obtained using the COSMIC spectrograph at Palomar, and gleaned from the literature. We are in the process of supplementing this data set with additional observations using other facilities. Although we do not claim that any of these galaxy samples are ‘complete’, we have endeavoured to ensure that they all come with known selection functions, allowing a statistical analysis to be performed. Completeness in this context would be rather an illusory concept, as there will always be weaker lines and less luminous or lower surface brightness galaxies that are missed by any survey. This point has been made by many authors including Linder (1998, 2000) and Rosenberg et al. (2003). The fields observed with MOS on the CFHT were chosen to include Key Project QSOs (Jannuzi et al. 1998) with QSO redshift greater than 0.5 and Faint Object Spectrograph (FOS) higher dispersion spectroscopy covering from redshift 0.34 to 1 (i.e., FOS gratings G190H and G270H). While UV spectroscopy down to z=0 is obviously desirable (and has been ...
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... comparing the distribution of galaxies and quasar absorption line systems shows some of the com- plexity of the phenomena at work. This can be illustrated by considering Figure 1. In this figure we show an image of the lines-of-sight (LOS) towards the QSOs LBQS 0107-025A and B. As discussed later in the paper, for this field we have samples of galaxies and Ly-α absorption line systems whose locations in this common volume of space can be compared. ...
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... final redshift distribution of this absorption line sample is shown in Figure 18. The dramatic drop in line numbers shortward of z∼0.35 is where Ly-α moves below the blue edge of the HST FOS G190H grating. ...
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... final redshift distribution of the galaxies with mea- sured redshifts is shown in Figure 19. ...
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... Figure 21 we show a pie diagram resulting from com- bining all of the LOS. This figure should allow the reader to understand our survey geometry and the regime over which our statistical results apply. ...
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... particular one can clearly see that our survey covers impact parameters out to 2 Mpc for redshifts above 0.45. One can also see that (because the KP observations did not include wavelengths shortward of Figure 19. Galaxy Sample Redshift distribution Figure 20. ...
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... can be seen in Figure 22, the average completeness peaks at around 60% at the bright end, falling smoothly to 20% at R∼20 and 10% at R∼21. This completeness can be taken as roughly referring to the volume enclosed by the solid line in the bottom panel of Figure 21. ...
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... such a small sample, it is impossible to draw any statistically con- vincing conclusions, but it is notable that all 5 galaxies so identified have at least one other galaxy close to it in red- shift. The clearest example is the absorber galaxy pair in the PG 2302+029 LOS at redshift 0.59 where there is a clear group or wall of galaxies at this redshift (see Figure 13). One possible inference, which could only be confirmed with a much larger sample, would be that large EW, large im- pact parameter 'pairs' are identified in somewhat overdense regions. ...
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... is consistent, for example, with the models of Davé et al. (1999). Figure 18 in that paper for example shows corre- lations in absorber-galaxy properties out to these sorts of scales. ...
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... prac- tice there is a (Poisson) error on our measurement of this background, which could be folded in to the analysis, but has not been in order to avoid overly complicated plots. Figure 31. Distribution of velocity difference and impact pa- rameter between galaxies and galaxies selected as described in the text. ...
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Citations
... The multi-object spectrograph on the Canada-France-Hawaii Telescope (CFHT-MOS) (Le Fevre et al. 1994) was used to obtain spectra for 29 galaxies in the Q0107 field, described in Morris & Jannuzi (2006), whilst VIMOS (LeFevre et al. 2003) took 935 spectra (ESO programs 086.A-0970, PI:Crighton; and 087.A-0857, PI: Tejos). 642 galaxies in this field were observed using DEIMOS (Faber et al. 2003, program A290D, PIs: Bechtold and Jannuzi), with 210 spectra added by GMOS (Davies et al. 1997. ...
We examine to what extent disk and outflow models can reproduce observations of H i gas within a few virial radii of galaxies in pairs and groups. Using highly-sensitive HST/COS and FOS spectra of the Q0107 quasar triplet covering Lyα for z≲1, as well as a deep galaxy redshift survey including VIMOS, DEIMOS, GMOS and MUSE data, we test simple disk and outflow models against the H i absorption along three lines-of-sight (separated by 200-500 kpc) through nine galaxy groups in this field. These can be compared with our previous results in which these models can often be fit to the absorption around isolated galaxies. Our models can reproduce ≈ 75% of the 28 identified absorption components within 500 km s−1 of a group galaxy, so most of the H i around groups is consistent with a superposition of the CGM of the individual galaxies. Gas stripped in interactions between galaxies may be a plausible explanation for some of the remaining absorption, but neither the galaxy images nor the galaxy and absorber kinematics provide clear evidence of such stripped material, and these unexplained absorbers do not preferentially occur around close pairs of galaxies. We find H i column densities typically higher than at similar impact parameters around isolated galaxies (≈ 2.5σ), as well as more frequent detections of O vi than around isolated galaxies (30% of sightlines to 7%).
... The multi-object spectrograph on the Canada-France-Hawaii Telescope (CFHT-MOS) (Le Fevre et al. 1994) was used to obtain spectra for 29 galaxies in the Q0107 field, described in Morris & Jannuzi (2006), whilst VIMOS (LeFevre et al. 2003) took 935 spectra (ESO programs 086.A-0970, PI:Crighton; and 087.A-0857, PI: Tejos). 642 galaxies in this field were observed using DEIMOS (Faber et al. 2003, program A290D, PIs: Bechtold and Jannuzi), with 210 spectra added by GMOS (Davies et al. 1997. ...
We examine to what extent disk and outflow models can reproduce observations of H I gas within a few virial radii of galaxies in pairs and groups. Using highly-sensitive HST/COS and FOS spectra of the Q0107 quasar triplet covering Ly$\alpha$ for z$\lesssim$1, as well as a deep galaxy redshift survey including VIMOS, DEIMOS, GMOS and MUSE data, we test simple disk and outflow models against the H I absorption along three lines-of-sight (separated by 200-500 kpc) through nine galaxy groups in this field. These can be compared with our previous results in which these models can often be fit to the absorption around isolated galaxies. Our models can reproduce $\approx$ 75$\%$ of the 28 identified absorption components within 500 km/s of a group galaxy, so most of the H I around groups is consistent with a superposition of the CGM of the individual galaxies. Gas stripped in interactions between galaxies may be a plausible explanation for some of the remaining absorption, but neither the galaxy images nor the galaxy and absorber kinematics provide clear evidence of such stripped material, and these unexplained absorbers do not preferentially occur around close pairs of galaxies. We find H I column densities typically higher than at similar impact parameters around isolated galaxies ($\approx$ 2.5$\sigma$), as well as more frequent detections of O VI than around isolated galaxies (30$\%$ of sightlines to 7$\%$).
... Both Paper 1 and T14 (with references therein) describe the data collection and reduction processes in more detail. The multi-object spectrograph on the Canada-France-Hawaii Telescope (CFHT-MOS; Le Fevre et al. 1994 ) was used to observe 29 galaxies in the Q0107 field (described in Morris & Jannuzi 2006 ). The VIMOS data (LeFevre et al. 2003 ) consist of 935 lowresolution ( R ∼ 200) spectra with co v erage between 5500 and 9500 Å (programs 086.A-0970, PI:Crighton; and 087.A-0857, PI: Tejos), reduced using VIPGI (Scodeggio et al. 2005 ). ...
We use H i absorption along the lines-of-sight to the Q0107 quasar triplet in order to model potential disc and outflow structures in the circumgalactic medium of intervening galaxies at z ≲ 1, as well as the intergalactic medium on scales of up to a few virial radii. We consider a sample of twelve isolated galaxies in the Q0107 field with position angles and inclinations measured from HST imaging as well as redshifts from our spectroscopic surveys, alongside 27 detected Ly α absorbers within 500 km s−1 of these galaxies. Building on previous work showing increased incidence of absorption close to the projected major and minor axes, we use model rotating discs and bi-conical outflows in attempting to reproduce the observed absorption. Requiring these models to match absorption in multiple lines-of-sight provides additional constraints over single-sightline observations. We identify four possible outflows with velocities ∼100 km s−1, two of which extend to or beyond the virial radius, with a variety of opening angles. Two galaxies have nearby co-rotating absorbers with rotation velocities ≲ vvir, that may probe disc-like structures, and we can rule out a disc/outflow origin for a further ten absorbers. These indicate that outflowing and co-rotating structures can extend to large scales but are either not ubiquitous, or do not always produce detectable Ly α. In some cases, disc models are successful even close to the minor axis of the galaxy, and some of our model outflows exhibit wide opening angles. These results imply that purely geometrical cuts are not sufficient to distinguish between discs and outflows in single line-of-sight studies.
... The multi-object spectrograph on the Canada-France-Hawaii Telescope (CFHT-MOS) (Le Fevre et al. 1994) was used for observing runs in 1995 and 1997 by Morris & Jannuzi (2006). The Q0107 field was observed on the 29th and 30th July 1995, producing 30 galaxy spectra (one object observed twice, so 29 objects). ...
We study the distribution and dynamics of the circum- and intergalactic medium using a dense galaxy survey covering the field around the Q0107 system, a unique z~1 projected quasar triplet. With full Ly$\alpha$ coverage along all three lines-of-sight from z=0.18 to z=0.73, more than 1200 galaxy spectra, and two MUSE fields, we examine the structure of the gas around galaxies on 100-1000 kpc scales. We search for H I absorption systems occurring at the same redshift (within 500 $\textrm{km}$ $\textrm{s}^{-1}$) in multiple sightlines, finding with $>$ 99.9% significance that these systems are more frequent in the observed quasar spectra than in a randomly distributed population of absorbers. This is driven primarily by absorption with column densities N(H I) $> 10^{14}$ $\textrm{cm}^{-2}$, whilst multi-sightline absorbers with lower column densities are consistent with a random distribution. Star-forming galaxies are more likely to be associated with multi-sightline absorption than quiescent galaxies. HST imaging provides inclinations and position angles for a subset of these galaxies. We observe a bimodality in the position angle of detected galaxy-absorber pairs, again driven mostly by high-column-density absorbers, with absorption preferentially along the major and minor axes of galaxies out to impact parameters of several hundred kpc. We find some evidence supporting a disk/outflow dichotomy, as H I absorbers near the projected major-axis of a galaxy show line-of-sight velocities that tend to align with the rotation of that galaxy, whilst minor-axis absorbers are twice as likely to exhibit O VI at the same redshift.
... z ≈ 1-2) is more limited, and primarily focused around either Ly α absorption or relatively low-ion absorbers such as Mg II and C IV (e.g. Chen et al. 1998;Bowen et al. 2006;Morris & Jannuzi 2006;Rubin et al. 2010;Lovegrove & Simcoe 2011;Farina et al. 2014;Johnson, Chen & Mulchaey 2015b). There are an increasing number of studies focusing on the relevance of large-scale structure (i.e. ...
We present the first results from a study of O vi absorption around galaxies at z < 1.44 using data from a near-infrared grism spectroscopic Hubble Space Telescope Large Programme, the Quasar Sightline and Galaxy Evolution (QSAGE) survey. QSAGE is the first grism galaxy survey to focus on the circumgalactic medium at z ∼ 1, providing a blind survey of the galaxy population. The galaxy sample is H α flux limited (f(H α) > 2 × 10−17 erg s−1 cm−2) at 0.68 < z < 1.44, corresponding to ≳0.2–0.8 M⊙ yr−1. In this first of 12 fields, we combine the galaxy data with high-resolution STIS and COS spectroscopy of the background quasar to study O vi in the circumgalactic medium. At z ∼ 1, we find O vi absorption systems up to b ∼ 350 kpc (∼4Rvir) from the nearest detected galaxy. Further, we find ${\sim }50{{\ \rm per\ cent}}$ of ≳1 M⊙ yr−1 star-forming galaxies within 2Rvir show no associated O vi absorption to a limit of at least N(O vi) = 1013.9 cm−2. That we detect O vi at such large distances from galaxies and that a significant fraction of star-forming galaxies show no detectable O vi absorption disfavours outflows from ongoing star formation as the primary medium traced by these absorbers. Instead, by combining our own low- and high-redshift data with existing samples, we find tentative evidence for many strong (N(O vi) > 1014 cm−2) O vi absorption systems to be associated with M⋆ ∼ 109.5–10 M⊙ mass galaxies (Mhalo ∼ 1011.5–12 M⊙ dark matter haloes), and infer that they may be tracing predominantly collisionally ionized gas within the haloes of such galaxies.
... Lanzetta et al. 1995;Chen et al. 1998Chen et al. , 2001. Morris & Jannuzi (2006) detected a significant correlation between H i absorbers and galaxies at separations of 1.5 Mpc, albeit weaker than the galaxy-galaxy autocorrelation. They found their results to be consistent with the absorbing gas and the galaxies coexisting in dark matter filaments and knots, consistent with predictions from models of galaxy formation. ...
We present an analysis of the spatial distribution of gas and galaxies using new X-Shooter observations of $z\sim3-4$ quasars. Adding the X-Shooter data to an existing dataset of high resolution quasar spectroscopy, we use a total sample of 29 quasars alongside $\sim1700$ Lyman Break Galaxies in the redshift range $2<z<3.5$. Analysing the Ly$\alpha$ forest auto-correlation function using the full quasar sample, we find $s_0=0.081\pm0.006h^{-1}$Mpc. We then investigate the clustering and dynamics of Ly$\alpha$ forest absorbers around $z\sim3$ LBGs. From the redshift-space cross-correlation, we find $s_0=0.27\pm0.14h^{-1}$Mpc, with power-law slope $\gamma=1.1\pm0.2$. We make a first analysis of the dependence of this clustering length on absorber strength based on cuts in the sightline transmitted flux, finding a clear preference for stronger absorption features to be more strongly clustered around the galaxy population than weaker absorption features. Further, we calculate the projected correlation function, finding $r_0=0.24\pm0.04h^{-1}$Mpc (assuming a fixed slope $\gamma=1.1$). Taking this as the underlying real-space clustering, we fit the 2D cross-correlation function with a dynamical model incorporating the infall parameter and the peculiar velocity, finding $\beta_{\rm F}=1.02\pm0.22$ and $240\pm60$ km s$^{-1}$ respectively. This result shows a significant detection of gas infall relative to the galaxy population, whilst the measured velocity dispersion is consistent with the velocity uncertainties on the galaxy redshifts. We evaluate the Cauchy-Schwarz inequality between the galaxy-galaxy, absorber-absorber, and galaxy-absorber correlation functions, finding a result significantly less than unity: $\xi_{\rm ag}^2/(\xi_{\rm gg}\xi_{\rm aa})=0.25\pm0.14$, implying that galaxies and Ly$\alpha$ absorbers do not linearly trace the underlying dark matter distribution in the same way.
... Kacprzak et al. , 2012Bouché et al. 2012Bouché et al. , 2013Tumlinson et al. 2013;Stocke et al. 2013;Péroux et al. 2013;Nielsen et al. 2013bNielsen et al. , 2015bWerk et al. 2014;Fumagalli et al. 2015); and on statistical scales: analysing the large scale distribution of gas around galaxies (e.g. Adelberger et al. 2003Adelberger et al. , 2005Ryan-Weber 2006;Morris & Jannuzi 2006;Chen & Mulchaey 2009;Crighton et al. 2011;Rudie et al. 2012;Rakic et al. 2012;Tejos et al. 2014;Tummuangpak et al. 2014;Turner et al. 2014Turner et al. , 2015Finn et al. 2016). ...
We present new MUSE observations of a galaxy group probed by a background quasar. The quasar sightline passes between multiple $z=0.28$ galaxies, whilst showing at the same redshift low ionised metal line species, including Ca II, Mg I, Mg II and Fe II. Based on the galaxy redshifts measured from the MUSE data, we estimate the galaxies to be part of a small galaxy group with a halo mass of $\approx6\times10^{12}$ M$_{\odot}$. We use the MUSE data to reveal the two dimensional dynamical properties of the gas and stars in the group galaxies, and relate these to the absorber kinematics. With these data we consider four scenarios for the nature of the gas probed by the sightline absorbers: a co-rotating gas halo associated with a single galaxy within the group; outflowing material from a single group member powered by recent star-formation; and cool dense gas embedded within the intra-group medium. We find that the dynamics, alongside the galaxy impact parameters and star-formation rates, favour the latter, in which the cool gas belongs to the intra-group medium and is likely pressure confined within a warmer gas halo.
... The galaxy data is obtained from a number of different instruments and surveys. We include data collected by our own collaboration from the Deep Imaging Multi-Object Spectrograph (DEIMOS), Gemini Multi-Object Spectrograph (GMOS), Canada-France-Hawaii Telescope (CFHT) multi-object spectrograph and Very Large Telescope (VLT) Visible Multi-Object Spectrograph (VIMOS) (hereafter, T14 and T14-Q0107; Morris & Jannuzi 2006;Tejos et al. 2014). We make use of the Sloan Digital Sky Survey (SDSS) (Abazajian et al. 2009), 2dF Galaxy Redshift Survey (2dFGRS) (Colless et al. 2001), Galaxy and Mass Assembly (GAMA) survey (Driver et al. 2011), VLT VIMOS Deep Survey (VVDS) (Le Fèvre et al. 2005) and VIMOS Public Extragalactic Redshift Survey (VIPERS) (Guzzo et al. 2014). ...
... 4 GMOS data was reduced using the Gemini Image Reduction and Analysis Facility (IRAF) (see Tejos et al. 2014, for details). The reduction of the CFHT data is described in Morris & Jannuzi (2006). SDSS, GAMA and 2dFGRS data reduction procedures are described in Stoughton et al. (2002), Hopkins et al. (2013) and Colless et al. (2001) respectively. ...
... The majority of the galaxy redshifts in our VIMOS, DEIMOS, GMOS and CFHT samples were obtained by cross-correlating galaxy, star and QSO templates from SDSS 11 with each observed spectrum (see Morris & Jannuzi 2006;Tejos et al. 2014, for a full description). Each galaxy was then assigned a quality flag to indicate the reliability of the assigned redshift. ...
We present new results on the auto- and cross-correlation functions of galaxies and O vi absorbers in a ∼18~Gpc3 comoving volume at z < 1. We use a sample of 51 296 galaxies and 140 O viabsorbers in the column density range 13 ≲ log N ≲ 15 to measure two-point correlation functions in the two dimensions transverse and orthogonal to the line-of-sight ξ(r⊥, r∥). We furthermore infer the corresponding ‘real-space’ correlation functions, ξ(r), by projecting ξ(r⊥, r∥) along r∥, and assuming a power-law form, ξ(r) = (r/r0)−γ. Comparing the results from the absorber-galaxy cross-correlation function, ξag, the galaxy auto-correlation function, ξgg, and the absorber auto-correlation function, ξaa, we constrain the statistical connection between galaxies and the metal-enriched intergalactic medium as a function of star-formation
activity. We also compare these results to predictions from the Eagle cosmological hydrodynamical simulation and find a reasonable agreement. We find that: (i) O vi absorbers show very little velocity dispersion with respect to galaxies on ∼ Mpc scales, likely ≲ 100 km s-1; (ii) O vi absorbers are less clustered, and potentially more extended around galaxies than galaxies are around themselves; (iii) On
≳ 100 kpc scales, the likelihood of finding O vi absorbers around star-forming galaxies is similar to the likelihood of finding O vi absorbers around non star-forming galaxies; and (iv) O vi absorbers are either not ubiquitous to galaxies in our sample, or their distribution around them is patchy on scales ≳ 100 kpc
(or both), at least for the column densities at which most are currently detected.
... A radio survey of intervening absorption systems was carried out by Gupta et al. (2007). Surveys for galaxies associated with intervening absorption systems were conducted for galaxies associated with diffuse Lyα absorption systems at z < 1 by Lanzetta et al. (1995a), Chen et al. (2005b), Jannuzi (2006), andRyan-Weber (2006), with Damped Lyα Absorbers by Chen and Lanzetta (2003), Cooke et al. (2005), and Cooke et al. (2006), and with metal absorption systems at z < 1 by Tumlinson et al. (2005), Prochaska et al. (2006), Stocke et al. (2006a) and Kacprzak et al. (2008), and at z > 1 by Adelberger et al. (2005). ...
Intergalactic space is filled with a pervasive medium of ionized gas, the Intergalactic Medium (IGM). A residual neutral fraction is detected in the spectra of Quasi-Stellar Objects at both low and high redshifts, revealing a highly fluctuating medium with temperatures characteristic of photoionized gas. The statistics of the fluctuations are well-reproduced by numerical gravity-hydrodynamics simulations within the context of standard cosmological structure formation scenarios. As such, the study of the IGM offers an opportunity to probe the nature of the primordial density fluctuations on scales unavailable to other methods. The simulations also suggest the IGM is the dominant reservoir of baryons produced by the Big Bang, and so the principal source of the matter from which galaxies formed. The detection of metal systems within the IGM shows that it was enriched by evolved stars early in its history, demonstrating an intimate connection between galaxy formation and the IGM. The author presents a comprehensive review of the current understanding of the structure and physical properties of the IGM and its relation to galaxies, concluding with comments on prospects for furthering the study of the IGM using future ground-based facilities and space-based experiments. Comment: 69 pages; accepted version to appear in Reviews of Modern Physics; text and equation typos corrected; all figures included
We study the distribution and dynamics of the circum- and intergalactic medium using a dense galaxy survey covering the field around the Q0107 system, a unique z ≈ 1 projected quasar triplet. With full Lyα coverage along all three lines-of-sight from z=0.18 to z=0.73, more than 1200 galaxy spectra, and two MUSE fields, we examine the structure of the gas around galaxies on 100-1000 kpc scales. We search for H i absorption systems occurring at the same redshift (within 500 km s−1) in multiple sightlines, finding with > 99.9 per cent significance that these systems are more frequent in the observed quasar spectra than in a randomly distributed population of absorbers. This is driven primarily by absorption with column densities N(H i) >1014 cm−2, whilst multi-sightline absorbers with lower column densities are consistent with a random distribution. Star-forming galaxies are more likely to be associated with multi-sightline absorption than quiescent galaxies. HST imaging provides inclinations and position angles for a subset of these galaxies. We observe a bimodality in the position angle of detected galaxy-absorber pairs, again driven mostly by high-column-density absorbers, with absorption preferentially along the major and minor axes of galaxies out to impact parameters of several hundred kpc. We find some evidence supporting a disk/outflow dichotomy, as H i absorbers near the projected major-axis of a galaxy show line-of-sight velocities that tend to align with the rotation of that galaxy, whilst minor-axis absorbers are twice as likely to exhibit O vi at the same redshift.
