This paper presents an absorption-line study of the multiphase circumgalactic medium (CGM) based on observations of Lyα, C II, C IV, Si II, Si III, and Si IV absorption transitions in the vicinities of 195 galaxies at redshift z < 0.176. The galaxy sample is established based on a cross-comparison between public galaxy and QSO survey data and is characterized by a median redshift of z = 0.041, a median projected distance of d = 362 kpc to the sightline of the background QSO, and a median stellar mass of log (M star /M ) = 9.7 ± 1.1. Comparing the absorber features identified in the QSO spectra with known galaxy properties has led to strong constraints for the CGM absorption properties at z < ∼ 0.176. First, abundant hydrogen gas is observed out to d ∼ 500 kpc, well beyond the dark matter halo radius R h of individual galaxies, with a mean covering fraction of ≈ 60%. In contrast, no heavy elements are detected at d > ∼ 0.7 R h from either low-mass dwarfs or high-mass galaxies. The lack of detected heavy elements in low-and high-ionization states suggests that either there exists a chemical enrichment edge at d ≈ 0.7 R h or gaseous clumps giving rise to the observed absorption lines cannot survive at these large distances. Considering all galaxies at d > R h leads to a strict upper limit for the covering fraction of heavy elements of ≈ 3% (at a 95% confidence level) over d = (1 − 9) R h . At d < R h , differential covering fraction between low-and high-ionization gas is observed, suggesting that the CGM becomes progressively more ionized from d < 0.3 R h to larger distances. Comparing CGM absorption observations at low and high redshifts shows that at a fixed-fraction of R h the CGM exhibits stronger mean absorption at z = 2.2 than at z ∼ 0 and that the distinction is most pronounced in low-ionization species traced by C II and Si II absorption lines. We discuss possible pseudo-evolution of the CGM as a result of misrepresentation of halo radius, and present a brief discussion on the implications of these findings.

Gravitational lensing of the cosmic microwave background generates a curl pattern in the observed polarization. This "B-mode" signal provides a measure of the projected mass distribution over the entire observable Universe and also acts as a contaminant for the measurement of primordial gravitywave signals. In this Letter we present the first detection of gravitational lensing B modes, using first-season data from the polarization-sensitive receiver on the South Pole Telescope (SPTpol). We construct a template for the lensing B-mode signal by combining E-mode polarization measured by SPTpol with estimates of the lensing potential from a Herschel -SPIRE map of the cosmic infrared background. We compare this template to the B modes measured directly by SPTpol, finding a non-zero correlation at 7.7σ significance. The correlation has an amplitude and scale-dependence consistent with theoretical expectations, is robust with respect to analysis choices, and constitutes the first measurement of a powerful cosmological observable. [2,3]. B modes are not generated at linear order in perturbation theory by the scalar perturbations which are the dominant source of CMB temperature and E-mode anisotropies. Because of this, B modes are of great interest as a clean probe of two more subtle signals: (1) primordial tensor perturbations in the early Universe [4,5], the measurement of which would provide a unique probe of the energy scale of inflation; and (2) gravitational lensing, which generates a distinctive nonGaussian B-mode signal [6] that can be used to measure the projected mass distribution and constrain cosmological parameters such as the sum of neutrino masses (for a review, see [7]).Previous experiments have placed upper limits on the B-mode polarization anisotropy [8][9][10][11]. In this Letter we present the first detection of B modes sourced by gravitational lensing, using first-season data from SPTpol, the polarization-sensitive receiver on the South Pole Telescope.Gravitational lensing remaps the observed position of CMB anisotropies asn →n+∇φ(n), where φ is the CMB lensing potential [12]. This remapping mixes some of the (relatively) large E-mode signal into B. The induced B mode at Fourier wavevector l B is given to first order in φ as [13]

We present a measurement of the cosmic microwave background (CMB) gravitational lensing potential using data from the first two seasons of observations with SPTpol, the polarization-sensitive receiver currently installed on the South Pole Telescope. The observations used in this work cover 100 deg 2 of sky with arcminute resolution at 150 GHz. Using a quadratic estimator, we make maps of the CMB lensing potential from combinations of CMB temperature and polarization maps. We combine these lensing potential maps to form a minimum-variance (MV) map. The lensing potential is measured with a signal-to-noise ratio of greater than one for angular multipoles between L 100 250 < <. This is the highest signal-to-noise mass map made from the CMB to date and will be powerful in cross-correlation with other tracers of large-scale structure. We calculate the power spectrum of the lensing potential for each estimator, and we report the value of the MV power spectrum between L 100 2000 < < as our primary result. We constrain the ratio of the spectrum to a fiducial ΛCDM model to be A MV = 0.92 ± 0.14 (Stat.) ± 0.08 (Sys.). Restricting ourselves to polarized data only, we find A POL = 0.92 ± 0.24 (Stat.) ± 0.11 (Sys.). This measurement rejects the hypothesis of no lensing at 5.9s using polarization data alone, and at 14s using both temperature and polarization data.

We analyze circumgalactic medium (CGM) in a suite of high-resolution cosmological resimulations of a Milky-Way size galaxy and show that CGM properties are quite sensitive to details of star formation-feedback loop modelling. The simulation that produces a realistic late-type galaxy, fails to reproduce existing observations of the CGM. In contrast, simulation that does not produce a realistic galaxy has the predicted CGM in better agreement with observations. This illustrates that properties of galaxies and properties of their CGM provide strong complementary constraints on the processes governing galaxy formation. Our simulations predict that column density profiles of ions are well described by an exponential function of projected distance d: N ∝ e −d/hs . Simulations thus indicate that the sharp drop in absorber detections at larger distances in observations does not correspond to a "boundary" of an ion, but reflects the underlying steep exponential column density profile. Furthermore, we find that ionization energy of ions is tightly correlated with the scale height h s : h s ∝ E 0.74 ion . At z ≈ 0, warm gas traced by low-ionization species (e.g., Mg II and C IV) has h s ≈ 0.03 − 0.07R vir , while higher ionization species (O VI and Ne VIII) have h s ≈ 0.32 − 0.45R vir . Finally, the scale heights of ions in our simulations evolve slower than the virial radius for z 2, but similarly to the halo scale radius, r s . Thus, we suggest that the column density profiles of galaxies at different redshifts should be scaled by r s rather than the halo virial radius.