Search

We present new ALMA continuum and spectral observations of the MUSE Ultra Deep Field (MUDF), a $2\times 2$ arcmin$^2$ region with ultradeep multiwavelength imaging and spectroscopy hosting two bright $z\approx 3.22$ quasars used to study intervening gas structures in absorption. Through a blind search for dusty galaxies, we identified a total of seven high-confidence sources, six of which with secure spectroscopic redshifts. We estimate galaxy dust and stellar masses ($M_{\rm dust}\simeq 10^{7.8-8.6}\,M_{\odot}$, $M_{\star}\simeq 10^{10.2-10.7}\,M_{\odot}$), as well as star formation rates (${\rm SFR}\simeq 10^{1.2-2.0}\,M_{\odot}\,{\rm yr^{-1}} $) which show that most of these galaxies are massive and dust-obscured similar to coeval (sub-)millimeter galaxies. All six spectroscopically-confirmed galaxies are within $500~\rm km~s^{-1}$ of metal absorption lines observed in the quasar sightlines, corresponding to $100\%$ association rate. We also find that four of these galaxies belong to groups in which they are among the most massive members. Within the multiple group galaxies associated to the same absorption system, the ALMA sources are not always the closest in projection, but they are often aligned with the gaseous structures in velocity space. This suggests that these massive galaxies occupy the center of the potential well of the gas structures traced in absorption. However, albeit the low number density of sources identified with ALMA, our study may indicate that absorbers seem to infrequently originate in the inner circumgalactic medium of these galaxies. Instead, they appear to be better tracers of the gas distributed in the large-scale structure that host them., Comment: 13 pages, 9 figures, 1 Appendix. Submitted to A&A

We have used the Atacama Large Millimeter/submillimeter Array (ALMA) to map CO(3-2) emission from a galaxy, DLA-B1228g, associated with the high-metallicity damped Lyman-$\alpha$ absorber at $z \approx 2.1929$ towards the QSO PKS B1228-113. At an angular resolution of $\approx0.32''\times0.24''$, DLA-B1228g shows extended CO(3-2) emission with a deconvolved size of $\approx0.78''\times0.18''$, i.e. a spatial extent of $\approx6.4$ kpc. We detect extended stellar emission from DLA-B1228g in a Hubble Space Telescope Wide Field Camera 3 F160W image, and find that H$\alpha$ emission is detected in a Very Large Telescope SINFONI image from only one side of the galaxy. While the clumpy nature of the F160W emission and the offset between the kinematic and physical centers of the CO(3-2) emission are consistent with a merger scenario, this appears unlikely due to the lack of strong H$\alpha$ emission, the symmetric double-peaked CO(3-2) line profile, the high molecular gas depletion timescale, and the similar velocity dispersions in the two halves of the CO(3-2) image. Kinematic modelling reveals that the CO(3-2) emission is consistent with arising from an axisymmetric rotating disk, with an exponential profile, a rotation velocity of $v_{rot}=328\pm7$ km s$^{-1}$, and a velocity dispersion of $\sigma_{v}=62\pm7$ km s$^{-1}$. The high value of the ratio $v_{rot}/\sigma_v$, $\approx5.3$, implies that DLA-B1228g is a rotation-dominated cold disk galaxy, the second case of a high-$z$ HI-absorption-selected galaxy identified with a cold rotating disk. We obtain a dynamical mass of $M_{dyn}= (1.5\pm0.1)\times10^{11}~M_\odot$, similar to the molecular gas mass of $\approx10^{11} M_\odot$ inferred from earlier CO(1-0) studies; this implies that the galaxy is baryon-dominated in its inner regions., Comment: 13 pages, 5 figures and 2 tables. Accepted for publication in ApJL

We present analysis of the mass-metallicity relation (MZR) for a sample of 67 [OIII]-selected star-forming galaxies at a redshift range of $z=1.99 - 2.32$ ($z_{\text{med}} = 2.16$) using \emph{Hubble Space Telescope} Wide Field Camera 3 grism spectroscopy from the Quasar Sightline and Galaxy Evolution (QSAGE) survey. Metallicities were determined using empirical gas-phase metallicity calibrations based on the strong emission lines [OII]3727,3729, [OIII]4959,5007 and H$\beta$. Star-forming galaxies were identified, and distinguished from active-galactic nuclei, via Mass-Excitation diagrams. Using $z\sim0$ metallicity calibrations, we observe a negative offset in the $z=2.2$ MZR of $\approx -0.51$ dex in metallicity when compared to locally derived relationships, in agreement with previous literature analysis. A similar offset of $\approx -0.46$ dex in metallicity is found when using empirical metallicity calibrations that are suitable out to $z\sim5$, though our $z=2.2$ MZR, in this case, has a shallower slope. We find agreement between our MZR and those predicted from various galaxy evolution models and simulations. Additionally, we explore the extended fundamental metallicity relation (FMR) which includes an additional dependence on star formation rate (SFR). Our results consistently support the existence of the FMR, as well as revealing an offset of $0.28\pm0.04$ dex in metallicity compared to locally-derived relationships, consistent with previous studies at similar redshifts. We interpret the negative correlation with SFR at fixed mass, inferred from an FMR existing for our sample, as being caused by the efficient accretion of metal-poor gas fuelling SFR at cosmic noon., Comment: 15 pages, 10 figures. This paper has been accepted for publication in MNRAS

We observed existence of periodic orbit in immune network under transitive solvable lie algebra. In this paper, we focus to develop condition of maximal Lie algebra for immune network model and use that condition to construct vector field of symmetry to study non linear pathogen model. We used two methods to obtain analytical structure of solution, namely normal generator and differential invariant function. Numerical simulation of analytical structure exhibits correlated periodic pattern growth under spatio temporal symmetry which is similar to linear dynamical simulation result. We used lie algebraric method to understand correlation between growth pattern and symmetry of dynamical system. We employ idea of using one parameter point group of transformation of variables under which linear manifold is retained. In procedure, we present the method of deriving Lie point symmetries, calculation of first integral and invariant solution for the ODE. We show the connection between symmetries and differential invariant solution of the ODE. The analytical structure of the solution exhibits periodic behavior around attractor in local domain, same behavior obtained through dynamical analysis., Comment: 15 pages, 9 figures(.eps)

Germanates are often used as structural analogs of planetary silicates. We have explored the high-pressure phase relations in Mg$_2$GeO$_4$ using diamond anvil cell experiments combined with synchrotron x-ray diffraction and computations based on density functional theory. Upon room temperature compression, forsterite-type Mg$_2$GeO$_4$ remains stable up to 30 GPa. At higher pressures, a phase transition to a forsterite-III type (Cmc21) structure was observed, which remained stable to the peak pressure of 105 GPa. Using a 3rd order Birch Murnaghan fit to the experimental data, we obtained V0 = 305.1 (3) {\AA}3, K0 = 124.6 (14) GPa and K0' = 3.86 (fixed) for forsterite- and V0 = 263.5 (15) {\AA}3, K0 = 175 (7) GPa and K0' = 4.2 (fixed) for the forsterite-III type phase. The forsterite-III type structure was found to be metastable when compared to the stable assemblage of perovskite/post-perovskite + MgO, as observed during laser-heating experiments. Understanding the phase relations and physical properties of metastable phases is crucial for studying the mineralogy of impact sites, understanding metastable wedges in subducting slabs and interpreting the results of shock compression experiments.

In this work, we develop model for neuronal degeneration based on polymer chain folding dynamics and their connectivity in various scale. In the first phase, we just developed the model and numerical simulation need to be complete in order to complete the mathematical development of the disease progression., Comment: 13 pages, 4 figures

We use a classical, microscopic model of point-like dipolarizable entities (a model that is standard in the case of positive polarizability) and investigate its behavior for simple cubic (sc), body-centered cubic (bcc), and face-centered cubic (fcc) crystals with one entity per primitive cell when the static polarizability of the entities is negative and the mutual interaction between the entities is taken into account. We find that the static electric susceptibility is bounded below due to an instability towards self-polarization but the lower permissible bound is negative definite in each case, i.e., the concept of negative static electric susceptibility remains robust, according to the model, when mutual interactions are taken into account. The usual Clausius-Mossotti relation between the static polarizability and the static electric susceptibility remains valid in the case of negative parameters, but only down to the lower permissible bound; the value of the bound depends on the crystal structure and is always unrelated to the asymptote of the Clausius-Mossotti curve. The lower permissible bounds of the static electric susceptibility are found to be -0.906 for sc, and -1.00 for bcc and fcc. These results confirm that, although the magnitude of the static electric susceptibility does not diverge in the negative case (as it can in the positive case), the magnitudes attainable in the negative case for condensed media may, nevertheless, be many orders of magnitude greater than those predicted previously for inverted vapors and gases. This is a promising result in relation to the development of potential new technologies that exploit the phenomenon., Comment: 32 pages, 3 figures, Supplemental Material available from corresponding author on request

A detailed investigation of Ba$_2$MnGe$_2$O$_7$ was performed in its low-temperature magnetoelectric state combining neutron diffraction with magnetization measurements on single crystals. In the paramagnetic state at 10 K, polarized neutron diffraction was applied to reveal the components of the susceptibility tensor. The crystal and magnetic structures below the antiferromagnetic transition temperature of $T_N \approx 4$ K were determined using unpolarized neutron diffraction. This data implies no structural phase transition from 10 K down to 2.5 K and is well described within the tetragonal space group $P\bar{4}2_1m$. We found that in zero magnetic field the magnetic space group is either $C_cmc2_1$ or $P_c2_12_12_1$ with antiferromagnetic order along the [110] or [100] directions, respectively, while neighboring spins along the [001] axis are ordered antiferromagnetically. A non-collinear spin arrangement due to small canting within the $ab$ plane is allowed by symmetry and observed experimentally. The ordered moment is found to be 3.24(3) $\mu_B$/Mn$^{2+}$ at 2.5 K and the temperature-field dependent magnetic phase diagram is mapped out by macroscopic magnetization. Distinct differences between the magnetic structure of Ba$_2$MnGe$_2$O$_7$ as compared to those of Ba$_2$CoGe$_2$O$_7$ and Ca$_2$CoSi$_2$O$_7$ are discussed.

We present results of an optical spectroscopic survey using SALT and NOT to build a WISE mid-infrared color-based, dust-unbiased sample of powerful radio-bright ($>$200 mJy at 1.4 GHz) AGN for the MeerKAT Absorption Line Survey (MALS). Our sample has 250 AGN (median $z=1.8$) showing emission lines, 26 with no emission lines, and 27 without optical counterparts. Overall, our sample is fainter ($\Delta i$=0.6 mag) and redder ($\Delta(g-i)$=0.2 mag) than radio-selected quasars, and representative of fainter quasar population detected in optical surveys. About 20% of the sources are narrow line AGN (NLAGN) $-$ 65% of these, at $z < 0.5$ are galaxies without strong nuclear emission, and 10% at $z>1.9$, have emission line ratios similar to radio galaxies. The farthest NLAGN in our sample is M1513$-$2524 ($z_{em}=3.132$), and the largest (size$\sim$330 kpc) is M0909$-$3133 ($z_{em}=0.884$). We discuss in detail 110 AGN at $1.9 < z < 3.5$. Despite representing the radio loudest quasars (median $R$=3685), their Eddington ratios are similar to the SDSS quasars having lower $R$. We detect 4 CIV BALQSOs, all among AGN with least $R$, and highest black hole masses and Eddington ratios. The BAL detection rate ($4^{+3}_{-2}$%) is consistent with that seen in extremely powerful ($L_{1.4GHz}>10^{25}$ WHz$^{-1}$) quasars. Using optical light-curves, radio polarization and $\gamma$-ray detections, we identify 7 high-probability BL Lacs. We also summarize the full MALS footprint to search for HI 21-cm and OH 18-cm lines at $z<2$., Comment: 62 pages, 15 figures and 3 tables; accepted in ApJ (updated the redshift of M1312-2026 to z=0.977)

We try to obtain meromorphic solution of Time dependent Schroedinger equation which partially satisfies Painleve Integrable property. Our study and analysis exhibits meromorphic behavior of classical particle trajectory. In other words, particle is confined in punctured complex domain in singular fundamental domain. . We have explicitly developed solution from Jacobi Elliptic function and pole expansion approach in which solution remains meromorphic . Branch point analysis also shows solution branches out near such singular point. Meromorphic behavior is significant for a classical particle within quantum limit., Comment: Key word: movable singularity, Non Linear ODE, Meromorphic solution

We present results from a spectroscopically blind search for associated and intervening HI 21-cm and OH 18-cm absorption lines towards 88 AGNs at $2\le z\le5$ using the upgraded Giant Metrewave Radio Telescope (uGMRT). The sample of AGNs with 1.4 GHz spectral luminosity in the range, $10^{27 - 29.3}$ W/Hz, is selected using mid-infrared colors and closely resembles the distribution of the underlying quasar population. The search for associated or proximate absorption, defined to be within 3000 km/s of the AGN redshift, led to one HI 21-cm absorption detection (M1540-1453; $z_{abs}$= 2.1139). This is only the fourth known absorption at $z>2$. The detection rate ($1.6^{+3.8}_{-1.4}$%) suggests low covering factor of cold neutral medium (CNM; T$\sim$100 K) associated with these powerful AGNs. The intervening absorption line search, with a sensitivity to detect CNM in damped Ly$\alpha$ systems (DLAs), has comoving absorption path lengths of $\Delta$X = 130.1 and 167.7 for HI and OH, respectively. The corresponding number of absorber per unit comoving path lengths are $\le$0.014 and $\le$0.011, respectively. The former is at least 4.5 times lower than that of DLAs and consistent with the CNM cross-section estimated using H$_2$ and CI absorbers at $z>2$. Our AGN sample is optically fainter compared to the quasars used to search for DLAs in the past. In our optical spectra obtained using the Southern African Large Telescope (SALT) and the Nordic Optical Telescope (NOT), we detect 5 intervening (redshift path$\sim9.3$) and 2 proximate DLAs. This is slightly excessive compared to the statistics based on optically selected quasars. The non-detection of HI 21-cm absorption from these DLAs suggests small CNM covering fraction around galaxies at $z>2$., Comment: 23 pages, 14 figures and 4 tables; accepted in ApJS

The Large Survey Project (LSP) "MeerKAT Absorption Line Survey" (MALS) is a blind HI 21-cm and OH 18-cm absorption line survey in the L- and UHF-bands, with the primary goal to better determine the occurrence of atomic and molecular gas in the circum-galactic and inter-galactic medium, and its redshift evolution. Here we present the first results using the UHF-band, obtained towards the strongly lensed radio source PKS1830, detecting absorption in the lens galaxy. With merely 90min of data acquired on-source for science verification and processed using the Automated Radio Telescope Imaging Pipeline (ARTIP), we detect in absorption the known HI 21-cm and OH 18-cm main lines at z=0.89 at an unprecedented signal-to-noise ratio (4000 in the continuum, with 6km/s channels). For the first time we report the detection at z=0.89 of OH satellite lines, so far not detected at z $>$ 0.25. We decompose the OH lines into a thermal and a stimulated contribution, where the 1612 and 1720MHz lines are conjugate. The total OH 1720MHz emission line luminosity is 6100Lsun. This is the most luminous known 1720MHz maser line. The absorption components of the different images of the background source sample different light paths in the lensing galaxy, and their weights in the total absorption spectrum are expected to vary in time, on daily and monthly time scales. We compare our normalized spectra with those obtained more than 20 yrs ago, and find no variation. We interpret the absorption spectra with the help of a lens galaxy model, derived from an N-body hydro-dynamical simulation, with a morphology similar to its optical HST image. It is possible to reproduce the observations without invoking any central gas outflows. There are, however, distinct and faint high-velocity features, most likely high-velocity clouds. These clouds may contribute to broaden the HI and OH spectra., Comment: 13 pages, 11 figures, accepted in Astronomy and Astrophysics

We present details of the Automated Radio Telescope Imaging Pipeline (ARTIP) and results of a sensitive blind search for HI and OH absorbers at $z<0.4$ and $z<0.7$, respectively. ARTIP is written in Python 3.6, extensively uses the Common Astronomy Software Application (CASA) tools and tasks, and is designed to enable the geographically-distributed MeerKAT Absorption Line Survey (MALS) team to collaboratively process large volumes of radio interferometric data. We apply it to the first MALS dataset obtained using the 64-dish MeerKAT radio telescope and 32K channel mode of the correlator. With merely 40 minutes on target, we present the most sensitive spectrum of PKS1830-211 ever obtained and characterize the known HI ($z=0.19$) and OH ($z=0.89$) absorbers. We further demonstrate ARTIP's capabilities to handle realistic observing scenarios by applying it to a sample of 72 bright radio sources observed with the upgraded Giant Metrewave Radio Telescope (uGMRT) to blindly search for HI and OH absorbers. We estimate the numbers of HI and OH absorbers per unit redshift to be $n_{21}(z\sim0.18)<$0.14 and $n_{\rm OH}(z\sim0.40)<$0.12, respectively, and constrain the cold gas covering factor of galaxies at large impact parameters (50 kpc $<\rho<$ 150 kpc) to be less than 0.022. Due to the small redshift path, $\Delta z\sim$13 for HI with column density$>5.4\times10^{19}$ cm$^{-2}$, the survey has probed only the outskirts of star-forming galaxies at $\rho>30$ kpc. MALS with the expected $\Delta z\sim10^{3-4}$ will overcome this limitation and provide stringent constraints on the cold gas fraction of galaxies in diverse environments over $0

Measurements of the cosmic far-infrared background (CIB) indicate that emission from many extragalactic phenomena, including star formation and black hole accretion, in the Universe can be obscured by dust. Resolving the CIB to study the population of galaxies in which this activity takes place is a major goal of submillimetre astronomy. Here, we present interferometric 650$\mu$m submillimetre number counts. Using the Band 8 data from the ALMACAL survey, we have analysed 81 ALMA calibrator fields together covering a total area of 5.5~arcmin$^2$. The typical central rms in these fields is $\sim 100 \mu$Jy~beam$^{-1}$ with the deepest maps reaching $\sigma = 47 \mu$Jy~beam$^{-1}$ at sub-arcsec resolution. Multi-wavelength coverage from ALMACAL allows us to exclude contamination from jets associated with the calibrators. However, residual contamination by jets and lensing remain a possibility. Using a signal-to-noise threshold of $4.5\sigma$, we find 21 dusty, star-forming galaxies with 650$\mu$m flux densities of $\geq 0.7 $mJy. At the detection limit we resolve $\simeq 100$ per cent of the CIB at 650$\mu$m, a significant improvement compared to low resolution studies at similar wavelength. We have therefore identified all the sources contributing to the EBL at 650 microns and predict that the contribution from objects with flux 0.7

Deep galaxy surveys have revealed that the global star formation rate (SFR) density in the Universe peaks at 1 < z < 2 and sharply declines towards z = 0. But a clear picture of the underlying processes, in particular the evolution of cold atomic (~100 K) and molecular gas phases, that drive such a strong evolution is yet to emerge. MALS is designed to use MeerKAT's L- and UHF-band receivers to carry out the most sensitive (N(HI)>10$^{19}$ cm$^{-2}$) dust-unbiased search of intervening HI 21-cm and OH 18-cm absorption lines at 0 < z < 2. This will provide reliable measurements of the evolution of cold atomic and molecular gas cross-sections of galaxies, and unravel the processes driving the steep evolution in the SFR density. The large sample of HI and OH absorbers obtained from the survey will (i) lead to tightest constraints on the fundamental constants of physics, and (ii) be ideally suited to probe the evolution of magnetic fields in disks of galaxies via Zeeman Splitting or Rotation Measure synthesis. The survey will also provide an unbiased census of HI and OH absorbers, i.e. cold gas associated with powerful AGNs (>10$^{24}$ W Hz$^{-1}$) at 0 < z < 2, and will simultaneously deliver a blind HI and OH emission line survey, and radio continuum survey. Here, we describe the MALS survey design, observing plan and the science issues to be addressed under various science themes., Comment: 16 pages, 3 figures Accepted for publication, Proceedings of Science, Workshop on "MeerKAT Science: On the Pathway to the SKA", held in Stellenbosch 25-27 May, 2016

We present the results from our search for HI 21-cm absorption in a sample of 16 strong FeII systems ($W_{\rm r}$(MgII $\lambda2796$) $\ge1.0$ \AA\ and $W_{\rm r}$(FeII $\lambda2600$) or $W_{\rm FeII}$ $\ge1$ \AA) at $0.5

We present the results from our survey of HI 21-cm absorption, using GMRT, VLA and WSRT, in a sample of 55 z<0.4 galaxies towards radio sources with impact parameters (b) in the range ~0-35 kpc. In our primary sample (defined for statistical analyses) of 40 quasar-galaxy-pairs (QGPs), probed by 45 sightlines, we have found seven HI 21-cm absorption detections, two of which are reported here for the first time. Combining our primary sample with measurements having similar optical depth sensitivity ($\int\tau dv$ <= 0.3 km/s) from the literature, we find a weak anti-correlation (rank correlation coefficient = -0.20 at 2.42sigma level) between $\int\tau dv$ and b, consistent with previous literature results. The covering factor of HI 21-cm absorbers (C_21) is estimated to be 0.24 (+0.12/-0.08) at b <= 15 kpc and 0.06 (+0.09/-0.04) at b = 15-35 kpc. $\int\tau dv$ and C_21 show similar declining trend with radial distance along the galaxy's major axis and distances scaled with the effective HI radius. There is also tentative indication that most of the HI 21-cm absorbers could be co-planar with the extended HI discs. No significant dependence of $\int\tau dv$ and C_21 on galaxy luminosity, stellar mass, colour and star formation rate is found, though the HI 21-cm absorbing gas cross-section may be larger for the luminous galaxies. The higher detection rate (by a factor of ~4) of HI 21-cm absorption in z<1 DLAs compared to the QGPs indicates towards small covering factor and patchy distribution of cold gas clouds around low-z galaxies., Comment: 25 pages + 17 pages appendix, 12 figures, 5 tables, accepted for publication in MNRAS

This paper features and elaborates recent developments and modifications in asymptotic techniques in solving differential equation in non linear dynamics. These methods are proved to be powerful to solve weakly as well as strongly non linear cases. Obtained approximate analytical solutions are valid for the whole solution domain. In this paper, limitations of traditional perturbation methods are illustrated with various modified techniques. Mathematical tools such as variational approach, homotopy and iteration technique are discussed to solve various problems efficiently. Asymptotic methods such as Variational Method, modified Lindstedt-Poincare method, Linearized perturbation method, Parameter Expansion method, Homotopy Perturbation method and Perturbation-Iteration methods(singular and non singular cases) have been discussed in various situations. Main emphasis is given on Singular perturbation method and WKB method in various numerical problems., Comment: submit, to appear in Journal of Non Linear Science and Applications, 2016

In this report, Mathematical model for generalized nonlinear three dimensional wave breaking equations was de- veloped analytically using fully nonlinear extended Boussinesq equations to encompass rotational dynamics in wave breaking zone. The three dimensional equations for vorticity distributions are developed from Reynold based stress equations. Vorticity transport equations are also developed for wave breaking zone. This equations are basic model tools for numerical simulation of surf zone to explain wave breaking phenomena. The model reproduces most of the dynamics in the surf zone. Non linearity for wave height predictions is also shown close to the breaking both in shoaling as well as surf zone. Keyword Wave breaking, Boussinesq equation, shallow water, surf zone. PACS : 47.32-y, Comment: arXiv admin note: substantial text overlap with arXiv:physics/0503073

We present a detailed analysis of a H2-bearing metal-rich sub-damped Lyman-alpha system at zabs = 0.10115 towards the radio-loud quasar J0441-4313, at a projected separation of ~7.6 kpc from a star-forming galaxy. The H2, C I and Na I absorption are much stronger in the redder of the two components seen in the Hubble Space Telescope / Cosmic Origins Spectrograph spectrum. The best single component fit to the strong H2 component gives log N(H2) = 16.61 +/- 0.05. However, possible hidden saturation in the medium resolution spectrum can allow for log N(H2) to be as high as 18.9. The rotational excitation temperature of H2 in this component is 133 +33/-22 K. Photoionization models suggest 30-80% of the total N(H I) is associated with the strong H2 component, that has a density <= 100 cm^-3 and is subject to a radiation field that is <= 0.5 times the Galactic mean field. The Very Large Baseline Array 1.4 GHz continuum image of the radio source contains only 27% of the arcsecond scale emission. Using a previously published spectrum, no 21-cm absorption is found to be associated with the strong H2 component. This suggests that either the N(H I) associated with this component is <= 50% of the total N(H I) or the gas covering factor is <= 0.27. This is consistent with the results of the photoionization model that uses UV radiation due to stars in the associated galaxy. The 21-cm absorption previously reported from the weaker H2 component suggests a spin temperature of <= 90 K, at odds with the weakness of H2, C I and Na I absorption in this component. From the inferred physical and chemical conditions, we suggest that the gas may be tracing a recent metal-rich outflow from the host-galaxy., Comment: 13 pages, 5 figures, 4 tables, Accepted for publication in the MNRAS

We present a detailed high spectral resolution (R $\sim$ 40000) study of five high-z damped Lyman $\alpha$ systems (DLAs) and one sub-DLA detected along four QSO sightlines. Four of these DLAs are very metal-poor with [Fe/H] $\le$ $-$2. One of them, at z$_{abs}$ = 4.20287 towards J0953$-$0504, is the most metal-poor DLA at z $>$ 4 known till date. This system shows no enhancement of C over Fe and O, and standard Population II star yields can explain its relative abundance pattern. The DLA at z$_{abs}$ = 2.34006 towards J0035$-$0918 has been claimed to be the most carbon-enhanced metal-poor DLA. However, we show that thermal broadening is dominant in this system and, when this effect is taken into account, the measured carbon enhancement ([C/Fe] = 0.45 $\pm$ 0.19) becomes $\sim$ 10 times less than what was reported previously. The gas temperature in this DLA is estimated to be in the range of 5000 $-$ 8000 K, consistent with a warm neutral medium phase. From photoionization modelling of two of the DLAs showing C II* absorption, we find that the metagalactic background radiation alone is not sufficient to explain the observed C II* cooling rate, and local heating sources, probably produced by in-situ star formation, are needed. Cosmic ray heating is found to contribute $\gtrsim$ 60% to the total heating in these systems. Using a sample of metal-poor DLAs with C II* measurements, we conclude that the cosmic ray ionization rate is equal to or greater than that seen in the Milky Way in $\sim$ 33% of the systems with C II* detections., Comment: 21 pages, 17 figures, 8 tables, Accepted for publication in the MNRAS