We performed a detailed study of the extended cool gas, traced by MgII absorption \(W_r(2796)\geq0.3\)~Å, surrounding 14 narrow-line active galactic nuclei (AGNs) at 0.12<z<0.22 using background ...quasar sight-lines. The background quasars probe the AGNs at projected distances of \(60\leq D\leq265\)~kpc. We find that, between \(100\leq D\leq200\)~kpc, AGNs appear to have lower MgII gas covering fractions (0.09\(^{+0.18}_{-0.08}\)) than quasars (0.47\(^{+0.16}_{-0.15}\)) and possibly lower than in active field galaxies (0.25\(^{+0.11}_{-0.09}\)). We do not find a statistically significant azimuthal angle dependence for the MgII covering fraction around AGNs, though the data hint at one. We also study the `down-the-barrel' outflow properties of the AGNs themselves and detect intrinsic NaID absorption in 8/8 systems and intrinsic MgII absorption in 2/2 systems, demonstrating that the AGNs have significant reservoirs of cool gas. We find that 6/8 NaID and 2/2 MgII intrinsic systems contain blueshifted absorption with \(\Delta v>50\) km/s, indicating outflowing gas. The 2/2 intrinsic MgII systems have outflow velocities a factor of \(\sim4\) higher than the NaID outflow velocities. Our results are consistent with AGN-driven outflows destroying the cool gas within their halos, which dramatically decreases their cool gas covering fraction, while star-burst driven winds are expelling cool gas into their circumgalactic media (CGM). This picture appears contrary to quasar--quasar pair studies which show that the quasar CGM contains significant amounts of cool gas whereas intrinsic gas found `down-the-barrel' of quasars reveals no cool gas. We discuss how these results are complementary and provide support for the AGN unified model.
The spectrograph ESPRESSO recently obtained a limit on the variation of the fine-structure constant, \(\alpha\), through measurements along the line of sight of a bright quasar with a precision of ...\(1.36\) ppm at \(1\sigma\) level. This imposes new constraints on cosmological models with a varying \(\alpha\). We assume such a model where the electromagnetic sector is coupled to a scalar field dark energy responsible for the current acceleration of the Universe. We parametrise the variation of \(\alpha\) with two extra parameters, one defining the cosmological evolution of the quintessence component and the other fixing the coupling with the electromagnetic field. The objective of this work is to constrain these parameters with both astrophysical and local probes. We also carried out a comparative analysis of how each data probe may constrain our parametrisation. We performed a Bayesian analysis by comparing the predictions of the model with observations. The astrophysical datasets are composed of quasar spectra measurements, including the latest ESPRESSO data point, as well as Planck observations of the cosmic microwave background. We combined these with local results from atomic clocks and the MICROSCOPE experiment. The constraints placed on the quintessence parameter are consistent with a null variation of the field, and are therefore compatible with a \(\Lambda\)CDM cosmology. The constraints on the coupling to the electromagnetic sector are dominated by the E\"otv\"os parameter local bound. More precise measurements with ESPRESSO will be extremely important to study the cosmological evolution of \(\alpha\) as it probes an interval of redshift not accessible to other types of observations. However, for this particular model, current available data favour a null variation of \(\alpha\) resulting mostly from the strong MICROSCOPE limits.
We present the first large, blind and uniformly selected survey for molecular hydrogen (H_2) in damped Lyman alpha systems (DLAs) with moderate-to-high resolution spectra. 86 DLAs were searched for ...absorption in the many Lyman and Werner H_2 transitions, with approximately 79% completeness for H_2 column densities above N(H_2)=10^17.5 cm^-2 for an assumed Doppler broadening parameter b=2 km s^-1. Only a single strong H_2 absorber was found -- a system detected previously in VLT/UVES spectra. Given our distribution of N(H_2) upper limits, this ~1% detection rate is smaller than expected from previous surveys at 99.8% confidence. Assuming the N(H_2) distribution shape from previous surveys, our detection rate implies a covering factor of ~1% for N(H_2) >= 10^17.5 cm^-2 gas in DLAs (<6% at 95% confidence). We obtained new Magellan/MagE spectra for 53 DLAs; 8 km s^-1 -resolution spectra were available for 27 DLAs. MagE's moderate resolution (~71 km s^-1) yields weaker N(H_2) upper limits and makes them dependent on the assumed Doppler parameter. For example, half the (relevant) previous H_2 detections have N(H_2) >= 10^18.1 cm^-2, a factor of just 3 higher than our median upper limit. Nevertheless, several tests suggest our upper limits are accurate, and they would need to be increased by 1.8 dex to bring our detection rate within 95% confidence of previous surveys.
By applying a display ecology to the {\em Deeper, Wider, Faster} proactive, simultaneous telescope observing campaign, we have shown a dramatic reduction in the time taken to inspect DECam CCD images ...for potential transient candidates and to produce time-critical triggers to standby telescopes. We also show how facilitating rapid corroboration of potential candidates and the exclusion of non-candidates improves the accuracy of detection; and establish that a practical and enjoyable workspace can improve the experience of an otherwise taxing task for astronomers. We provide a critical road-test of two advanced displays in a research context -- a rare opportunity to demonstrate how they can be used rather than simply discuss how they might be used to accelerate discovery.
According to the photo-heating model of the intergalactic medium (IGM), He II reionization is expected to affect its thermal evolution. Evidence for additional energy injection into the IGM has been ...found at \(3\lesssim z\lesssim4\), though the evidence for the subsequent fall-off below \(z\sim2.8\) is weaker and depends on the slope of the temperature--density relation, \(\gamma\). Here we present, for the first time, an extension of the IGM temperature measurements down to the atmospheric cut-off of the H I Lyman-\(\alpha\) forest at \(z\simeq1.5\). Applying the curvature method on a sample of 60 UVES spectra we investigated the thermal history of the IGM at \(z<3\) with precision comparable to the higher redshift results. We find that the temperature of the cosmic gas traced by the Ly-\(\alpha\) forest \(T(\bar{\Delta})\) increases for increasing overdensity from \(T(\bar{\Delta})\sim 22670\) K to 33740 K in the redshift range \(z\sim2.8-1.6\). Under the assumption of two reasonable values for \(\gamma\), the temperature at the mean density (\(T_{0}\)) shows a tendency to flatten at \(z\lesssim 2.8\). In the case of \(\gamma\sim1.5\), our results are consistent with previous ones which indicate a falling \(T_{0}\) for redshifts \(z\lesssim2.8\). Finally, our \(T(\bar{\Delta})\) values show reasonable agreement with moderate blazar heating models.
Molecular hydrogen (H2) absorption features observed in the line-of-sight to Q2348-011 at redshift zabs = 2.426 are analysed for the purpose of detecting a possible variation of the ...proton-to-electron mass ratio mu=mp/me. By its structure Q2348-011 is the most complex analysed H2 absorption system at high redshift so far, featuring at least seven distinctly visible molecular velocity components. The multiple velocity components associated with each transition of H2 were modeled simultaneously by means of a comprehensive fitting method. The fiducial model resulted in dmu/mu = (-0.68 +/- 2.78) x 10^-5, showing no sign that mu in this particular absorber is different from its current laboratory value. Although not as tight a constraint as other absorbers have recently provided, this result is consistent with the results from all previously analysed H2-bearing sight-lines. Combining all such measurements yields a constraint of dmu/mu < 10^-5 for the redshift range z = (2--3).
We report the discovery of deuterium absorption in the very metal-poor (Fe/H = -2.88) damped Lyman-alpha system at z_abs = 3.06726 toward the QSO SDSS J1358+6522. On the basis of 13 resolved D I ...absorption lines and the damping wings of the H I Lyman alpha transition, we have obtained a new, precise measure of the primordial abundance of deuterium. Furthermore, to bolster the present statistics of precision D/H measures, we have reanalyzed all of the known deuterium absorption-line systems that satisfy a set of strict criteria. We have adopted a blind analysis strategy (to remove human bias), and developed a software package that is specifically designed for precision D/H abundance measurements. For this reanalyzed sample of systems, we obtain a weighted mean of (D/H)_p = (2.53 +/- 0.04) x 10^-5, corresponding to a Universal baryon density100 Omega_b h^2 = 2.202 +/- 0.046 for the standard model of Big Bang Nucleosynthesis. By combining our measure of (D/H)_p with observations of the cosmic microwave background, we derive the effective number of light fermion species, N_eff = 3.28 +/- 0.28. We therefore rule out the existence of an additional (sterile) neutrino (i.e. N_eff = 4.046) at 99.3 percent confidence (2.7 sigma), provided that N_eff and the baryon-to-photon ratio (eta_10) did not change between BBN and recombination. We also place a strong bound on the neutrino degeneracy parameter, xi_D = +0.05 +/- 0.13 based only on the CMB+(D/H)_p observations. Combining xi_D with the current best literature measure of Y_p, we find |xi| <= +0.062. In future, improved measurements of several key reaction rates, in particular d(p,gamma)3He, and further measures of (D/H)_p with a precision comparable to those considered here, should allow even more stringent limits to be placed on new physics beyond the standard model.
Lyman Limit systems (LLSs) trace the low-density circumgalactic medium and the most dense regions of the intergalactic medium, so their number density and evolution at high redshift, just after ...reionisation, are important to constrain. We present a survey for LLSs at high redshifts, \(z_{\rm LLS} =3.5\)--5.4, in the homogeneous dataset of 153 optical quasar spectra at \(z \sim 5\) from the Giant Gemini GMOS survey. Our analysis includes detailed investigation of survey biases using mock spectra which provide important corrections to the raw measurements. We estimate the incidence of LLSs per unit redshift at \(z \approx 4.4\) to be \(\ell(z) = 2.6 \pm 0.4\). Combining our results with previous surveys at \(z_{\rm LLS} <4\), the best-fit power-law evolution is \(\ell(z) = \ell_* (1+z)/4^\alpha\) with \(\ell_* = 1.46 \pm 0.11\) and \(\alpha = 1.70 \pm 0.22\) (68\% confidence intervals). Despite hints in previous \(z_{\rm LLS} <4\) results, there is no indication for a deviation from this single power-law soon after reionization. Finally, we integrate our new results with previous surveys of the intergalactic and circumgalactic media to constrain the hydrogen column density distribution function, \(f(N_{\rm HI},X)\), over 10 orders of magnitude. The data at \(z \sim 5\) are not well described by the \(f(N_{\rm HI},X)\) model previously reported for \(z \sim 2\)--3 (after re-scaling) and a 7-pivot model fitting the full \(z \sim 2\)--5 dataset is statistically unacceptable. We conclude that there is significant evolution in the shape of \(f(N_{\rm HI},X)\) over this \(\sim\)2 billion year period.
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, absolute magnitudes, and rest-frame colors to the B- and K-band on the AB system. We present galaxy properties and rest-frame MgII equivalent width, Wr(2796), versus galaxy redshift. The well-known anti-correlation between Wr(2796) and quasar-galaxy impact parameter, D, is significant to the 8 sigma level. The mean color of MAGIICAT galaxies is consistent with an Sbc galaxy for all redshifts. We also present B- and K-band luminosity functions for different Wr(2796) and redshift subsamples: "weak absorbing" Wr(2796) < 0.3 Ang, "strong absorbing" Wr(2796) > 0.3 Ang, low redshift (z < zmed), and high redshift (z > zmed), where zmed = 0.359 is the median galaxy redshift. Rest-frame color B-K correlates with M_K at the 8 sigma level for the whole sample but is driven by the strong absorbing, high redshift subsample (6 sigma). Using M_K as a proxy for stellar mass and examining the luminosity functions, we infer that in lower stellar mass galaxies, MgII absorption is preferentially detected in blue galaxies and the absorption is more likely to be weak.
Phys. Rev. Lett. 113, 123002 (2014) Spectra of molecular hydrogen (H$_2$) are employed to search for a possible
proton-to-electron mass ratio ($\mu$) dependence on gravity. The Lyman
transitions of ...H$_2$, observed with the Hubble Space Telescope towards white
dwarf stars that underwent a gravitational collapse, are compared to accurate
laboratory spectra taking into account the high temperature conditions ($T \sim
13\,000$ K) of their photospheres. We derive sensitivity coefficients $K_i$
which define how the individual H$_2$ transitions shift due to
$\mu$-dependence. The spectrum of white dwarf star GD133 yields a
$\Delta\mu/\mu$ constraint of $(-2.7\pm4.7_{\rm stat}\pm 0.2_{\rm
sys})\times10^{-5}$ for a local environment of a gravitational potential
$\phi\sim10^4\ \phi_\textrm{Earth}$, while that of G29$-$38 yields
$\Delta\mu/\mu=(-5.8\pm3.8_{\rm stat}\pm 0.3_{\rm sys})\times10^{-5}$ for a
potential of $2 \times 10^4$ $\phi_\textrm{Earth}$.
