We search for weak O VI absorption in the low-redshift intergalactic medium (IGM) using 82 high signal-to-noise quasar spectra obtained with the Cosmic Origins Spectrograph on board the Hubble Space Telescope. From this dataset, we compile a clean sample of 396 intervening Lyman-alpha (Lya) absorption lines with H I column densities log (N_HI) < 14.5, all of which lack individual O VI absorption with log (N_OVI ) > 13. We perform a spectral stacking analysis at the expected location of the O VI doublet, revealing O VI absorption with a statistical significance greater than 5σ, and measure an equivalent width of 1.7 ± 0.3 mA, corresponding to log (N_OVI ) = 12.14 ± 0.08. The stacked O VI absorption signal associated with strong Lya absorbers (13.5 <= log N_HI < 14.5) is significantly stronger than that associated with weaker Lya absorbers (12.5 <= log N_HI < 13.5). For the subset of 81 broad Lya absorbers (BLAs; b(HI) > 45 km/s), we obtain a marginal ∼3 σ O VI detection. Other than Si III, detected at 5σ, no associated metal lines are found. Cross-correlation of the Lya absorbers with galaxies indicates that 93

We present an analysis of a partial Lyman limit system at z = 0.87641 detected in the HST/COS spectrum of the background quasar LBQS 0107-0235. The absorber exhibits a simple kinematic structure, with the metal-lines and the H I Lyman-series absorption well described by a single component. Photoionization modeling yields a gas metallicity of one-tenth solar and a hydrogen number density of n_H ≈8.5 ×10^-4 cm^-3 (log_10(n_H/cm^-3) ≈-3.1). At the absorber redshift, the VLT/MUSE data show two galaxies (G1 and G2) at normalized impact parameters of ρ/R_vir ≈0.9 and velocity separations of |Δv| = 18 and 99 km s^-1, respectively, from the absorber. Both galaxies have rotating disks with stellar masses of M_* ≈6 ×10^9 and ≈2.2 ×10^10 M_⊙. Their 100-Myr-averaged star formation rates are ≈2.5 and ≈2.2 M_⊙ yr^-1, though their instantaneous rates place G2 on the star-forming main sequence and G1 above it, which is actively star-forming at this redshift. The absorber is positioned very close to the projected major axis of both galaxies. The absorber's orientation, kinematics, and sub-solar metallicity (log_10(Z/Z_⊙) = -1.05) are consistent with the absorption tracing a sub-solar metallicity inflowing stream, though a galaxy-galaxy interaction origin cannot be excluded. We discuss these scenarios in the context of cosmological simulations of cold-mode accretion and CGM gas flows around galaxies with halos of mass M_h ≲10^12 M_⊙.

Astronomy, of all the sciences, is possibly the one with the most public appeal across all age groups. This is also evidenced by the existence of a large number of planetaria and amateur astronomy societies, which are unique to the field. Astronomy is known as a ‘gateway science’, with the ability to attract students who then proceed to explore their interest in other STEM fields. Astronomy’s link to society is, therefore, substantive and diverse. This white paper analyses six key areas: outreach and communication, astronomy education, history and heritage, astronomy for development, diversity, and hiring practices for outreach personnel. The current status of each of these areas is described, followed by an analysis of what is needed for the future. A set of recommendations for institutions, funding agencies, and individuals are evolved for each specific area. This work outlines how the future astronomy-society connection should take shape and provides a road map for the various stakeholders involved.

The SSPACE Astrobiology Payload (SAP) series, starting with the SAP-1 project is designed to conduct in-situ microbiology experiments in low earth orbit. This payload series aims to understand the behaviour of microbial organisms in space, particularly those critical for human health, and the corresponding effects due to microgravity and solar/galactic radiation. SAP-1 focuses on studying Bacillus clausii and Bacillus coagulans, bacteria beneficial to humans. It aims to provide a space laboratory for astrobiology experiments under microgravity conditions. The hardware developed for these experiments is indigenous and tailored to meet the unique requirements of autonomous microbiology experiments by controlling pressure, temperature, and nutrition flow to bacteria. A rotating platform, which forms the core design, is innovatively utilised to regulate the flow and mixing of nutrients with dormant bacteria. The technology demonstration models developed at SSPACE have yielded promising results, with ongoing efforts to refine, adapt for space conditions, and prepare for integration with nanosatellites or space modules. The anticipated payload will be compact, approximately 1U in size (10cm x 10cm x 10cm), consume less than 5W power, and offer flexibility for various microbiological studies.

We present a spectroscopic and imaging analysis of the z_gal≈ 1.1334 ultra-strong MgII absorption system identified in the VLT/UVES spectrum of a background quasar located at ρ≈ 18 kpc from a star-forming galaxy. Low ionization metal lines like MgI, FeII, and CaII are also detected for this absorber. The HI lines are outside of the wavelength coverage. The MgII has a rest-frame equivalent width of W_r(2796) =3.185 +/- 0.032 A^∘, with the absorption spread across Δv ≈ 460 km s^-1 in several components. A component-by-component ionization modeling shows several of these components having solar and higher metallicities. The models also predict a total HI column density of log[N(HI)/cm^-2] ≈ 22.5, consistent with ultra-strong MgII absorbers being sub-Damped Lyman Alpha and Damped Lyman Alpha systems. The absorber is well within the virial radius of the nearest galaxy which has a stellar mass M_* = 4.7 × 10^10 M_⊙, and a star formation rate of ≈ 8.3 M_⊙ yr^-1. The absorption is along the projected major axis of the galaxy with a velocity spread that is wider than the galaxy's disk rotation. From the kinematic analysis of the absorber and the galaxy, the origin of the absorption can be attributed to a combination of circumgalactic gas structures, some corotating with the disk and the rest at line-of-sight velocities outside of the disk rotation.

Using data from the Galaxy and Mass Assembly (GAMA) survey, we investigate how galaxy properties correlate with the local environment, focusing on the two southern regions of the survey (G02 and G23) that have not previously been examined in this context. We employ two-point and marked correlation functions to quantify the environmental dependence of galaxy color, stellar mass, luminosity across the u, g, r, J, and K bands, as well as star formation rate (SFR) and specific star formation rate (sSFR). We also assess the impact of redshift incompleteness and cosmic variance on these clustering measurements. Our results show that u-r and g-r colors are most strongly correlated with local overdensity, followed by stellar mass. The sSFR exhibits a clear inverse relationship with density of the environment, consistent with the trend observed for u-band luminosity, which traces young stellar populations. In contrast, galaxies brighter in the g, J, and K bands preferentially inhabit denser regions. By comparing our measurements from the southern regions with those from the equatorial regions of GAMA, we find that cosmic variance does not significantly influence our conclusions. However, redshift incompleteness affects the clustering measurements, as revealed through comparisons of subsets within the G02 region. The measured correlations provide key constraints for models of galaxy assembly across mass and environment, while the environmental trends in color and near-infrared luminosity offer a means to trace stellar mass growth and quenching with redshift.

We present a spectroscopic and imaging analysis of the z gal ≈ 1.1334 ultrastrong Mg ii absorption system identified in the Very Large Telescope/UVES spectrum of a background quasar located at ρ ≈ 18 kpc from a star-forming galaxy. Low-ionization metal lines like Mg i , Fe ii , and Ca ii are also detected for this absorber. The H I lines are outside of the wavelength coverage. The Mg ii has a rest-frame equivalent width of W r (2796) = 3.185 ± 0.032 Å, with the absorption spread across Δ v ≈ 460 km s −1 in several components. A component-by-component ionization modeling shows several of these components having solar and higher metallicities. The models also predict a total h i column density of log [ N ( H I ) / cm − 2 ] ≈ 22.5 , consistent with ultrastrong Mg ii absorbers being sub–damped Ly α and damped Ly α systems. The absorber is well within the virial radius of the nearest galaxy, which has a stellar mass M * = 4.7 × 10 10 M ⊙ , and a star formation rate of ≈8.3 M ⊙ yr −1 . The absorption is along the projected major axis of the galaxy with a velocity spread that is wider than the galaxy’s disk rotation. From the kinematic analysis of the absorber and the galaxy, the origin of the absorption can be attributed to a combination of circumgalactic gas structures, some corotating with the disk and the rest moving at line-of-sight velocities outside of the disk rotation.

Context. Galaxy mergers play a crucial role in galaxy evolution. However, the correlation between mergers and the local environment of galaxies is not fully understood. Aims. We aim to address the question of whether galaxy mergers prefer denser or less dense environments by quantifying the spatial clustering of mergers and non-mergers. We use two different indicators to classify mergers and non-mergers – classification based on a deep learning technique (f) and non-parametric measures of galaxy morphology, Gini-M20 (g). Methods. We used a set of galaxy samples in the redshift range 0.1 < z < 0.15 from the Galaxy and Mass Assembly (GAMA) survey with a stellar mass cut of log(M⋆/M⊙) > 9.5. We measured and compared the two-point correlation function (2pCF) of the mergers and non-mergers classified using the two merger indicators f and g. We measured the marked correlation function (MCF), in which the galaxies were weighted by f to probe the environmental dependence of galaxy mergers. Results. We do not observe a statistically significant difference between the clustering strengths of mergers and non-mergers obtained using 2pCF. However, using the MCF measurements with f as a mark, we observe an anti-correlation between the likelihood of a galaxy being a merger and its environment. Our results emphasise the advantage of MCF over 2pCF in probing the environmental correlations. Conclusions. Based on the MCF measurements, we conclude that the galaxy mergers prefer to occur in the under-dense environments on scales > 50 h−1 kpc of the large-scale structure (LSS). We attribute this observation to the high relative velocities of galaxies in the densest environments that prevent them from merging.

ABSTRACT The pervasive presence of warm gas in galaxy haloes suggests that the circumgalactic medium (CGM) is multiphase in its ionization structure and complex in its kinematics. Some recent state-of-the-art cosmological galaxy simulations predict an azimuthal dependence of CGM metallicities. We investigate the presence of such a trend by analysing the distribution of gas properties in the CGM around 47 z < 0.7 galaxies from the Multiphase Galaxy Halos Survey determined using a cloud-by-cloud, multiphase, ionization modelling approach. We identify three distinct populations of absorbers: cool clouds (T ∼ 104.1 K) in photoionization equilibrium, warm–hot collisionally ionized clouds (T ∼ 104.5–105 K) affected by time-dependent photoionization, and hotter clouds (T ∼ 105.4–106 K) with broad O vi and Ly α absorption consistent with collisional ionization. We find that fragmentation can play a role in the origin of cool clouds, that warm–hot clouds are out of equilibrium due to rapid cooling, and that hotter clouds are representative of virialized halo gas in all but the lowest mass galaxies. The metallicities of clouds do not depend on the azimuthal angle or other galaxy properties for any of these populations. At face value, this disagrees with the simplistic model of the CGM with bipolar outflows and cold-mode planar accretion. However, the number of clouds per sightline is significantly larger close to the minor and major axes. This implies that the processes of outflows and accretion are contributing to these CGM cloud populations, and our sightlines are probing gas of mixed origins at all azimuthal angles in these low-redshift galaxies.

We report on the analysis of a multiphase Lyman limit system (LLS) at z = 0.39047 identified toward the background quasar FBQS J0209-0438. The O VI doublet lines associated with this absorber have a different profile from the low-ionization metals and H i. Ly alpha has a very broad H i (b approximate to 150 km s-1) component well-aligned with one of the O VI components. The Doppler b-parameters for the broad H i and O VI indicate gas with T = (0.8 - 2.0) x 106 K and a total hydrogen column density that is an order of magnitude larger than the cooler phase of gas responsible for the LLS. Observations by the Very Large Telescope MUSE show two moderately star-forming galaxies within rho less than or similar to 105 kpc and divided by Delta v divided by less than or similar to 130 km s-1 of the absorber, one of them a dwarf galaxy (M * approximate to 106 M circle dot) overlapping with the quasar point-spread function, and the other a larger galaxy (R 1/2 approximate to 4 kpc) with M * approximate to 3 x 1010 M circle dot and M h approximate to 7 x 1011 M circle dot, and the dwarf galaxy within its virial radius. Although the absorption is aligned with the extended major axis of the larger galaxy, the line-of-sight velocity of the absorbing gas is inconsistent with corotating accretion. The metallicity inferred for the LLS is lower than the gas phase [O/H] of the two galaxies. The mixture of cool and warm/hot gas phases for the absorbing gas and its proximity and orientation to the galaxy pair points to the LLS being a high-velocity gas in the combined halo environment of both galaxies.

We present an absorption line study of the physical and chemical properties of the Leo HI Ring and the Leo I Group as traced by 11 quasar sightlines spread over a 600 kpc X 800 kpc region. Using HST/COS G130/G160 archival observations as constraints, we couple cloud-by-cloud, multiphase, Bayesian ionization modeling with galaxy property information to determine the plausible origin of the absorbing gas along these sightlines. We search for absorption in the range 600 km/s - 1400 km/s consistent with the kinematics of the Leo Ring/Group. We find absorption plausibly associated with the Leo Ring towards five sightlines. Along three other sightlines, we find absorption likely to be associated with individual galaxies, intragroup gas, and/or large-scale filamentary structure. The absorption along these five sightlines is stronger in metal lines than expected from individual galaxies, indicative of multiple contributions, and of the complex kinematics of the region. We also identify three sightlines within a 7-degree X 6-degree field around the Leo Ring, along which we do not find any absorption. We find that the metallicities associated with the Leo Ring are generally high, with values between solar and several times solar. The inferred high metallicities are consistent with the origin of the ring as tidal debris from a major galaxy merger.

Blazars are some of the brightest ultraviolet (UV) and X-ray sources in the sky and are valuable probes of the elusive warm-hot intergalactic medium (WHIM; T similar or equal to 10(5) -10(7) K). However, many of the brightest blazars - called BL Lac objects such as 1ES 1553+113 - have quasi-featureless spectra and poorly constrained redshifts. Here, we significantly improve the precision of indirect redshift constraints for blazars based on the edge of the HILy alpha forest observed in their UV spectra. We develop a robust technique to constrain the redshift of a z < 0.5 active galactic nucleus (AGN) or blazar with a 1 sigma uncertainty of approximate to 0.01 using only the position of its highest redshift Ly alpha absorber with log N-H(I)/Cm-2 > 12.6. We use a large sample of 192 AGNs/quasi-stellar objects at 0.01 less than or similar to z less than or similar to 0.45 that have high-quality Cosmic Origins Spectrograph (COS) far-UV spectra to characterize the intrinsic scatter in the gap between the AGN redshift and the edge of their Ly alpha forest. We present new COS near-UV data for 1ES 1553+113 and confirm its redshift of z = 0.433 using our technique. We apply our Ly alpha-forest-based redshift estimation technique to nine additional blazars with archival Hubble Space Telescope UV spectra, most of which are key targets for future X-ray missions. Our inferred redshift constraints improve estimates for two BL Lacs (1ES 1118+424 and S5 0716+714) and are consistent with previous estimates for the rest. Our results emphasize the need to obtain further UV spectra of bright blazars, of which many have uncertain redshifts, in order to maximize the scientific value of future X-ray WHIM observations that will improve our understanding of galaxy evolution.

ABSTRACT Using HST/COS spectra of the twin quasar lines of sight Q 0107–025A & Q 0107–025B, we report on the physical properties, chemical abundances, and transverse sizes of a multiphase medium in a galaxy field at z = 0.399. The angular separation between the quasars corresponds to a physical separation of 520 kpc at the absorber redshift. The absorber towards Q 0107–025B is a partial Lyman limit system (pLLS) with $\log N({\mathrm{H}}{\small I})/\hbox{cm$^{-2}$}\approx 16.8$. The H i column density in the absorber along the other sightline is ≈ 2 orders of magnitude lower. The O vi along both sightlines have comparable column densities and broad b-values (b > 30 km s−1) whereas the low ionization lines are considerably narrower. The low ionization gas is inconsistent with the O vi when modelled assuming photoionization from the same phase. In both lines of sight, O vi and the broad H i coinciding, are best explained through collisional ionization in a cooling plasma with solar metallicity. Ionization models infer 1/10th solar metallicity for the pLLS and solar metallicity for the lower column density absorber along the other sightline. Within ± 250 km s−1 and 2 Mpc of projected distance from the sightlines 12 galaxies are identified, of which five are within 500 kpc. The twin sightlines are at normalized impact parameters of ρ ∼ 1.1Rvir, and ρ ∼ 0.8Rvir from a M* ∼ 1010.7 M⊙, L ∼ 0.07L*, and star formation rate (SFR) < 0.1 M⊙ yr−1 galaxy, potentially probing its CGM (circumgalactic medium). The next closest in normalized separation are a dwarf galaxy with M* ∼ 108.7 M⊙, and SFR ∼ 0.06 M⊙ yr−1, and an intermediate mass galaxy with M* ∼ 1010.0 M⊙, and SFR ∼ 3 M⊙ yr−1. Along both sightlines, O vi could be either tracing narrow transition temperature zones at the interface of low ionization gas and the hot halo of nearest galaxy, or a more spread-out warm component that could be gas bound to the circumgalactic halo or the intragroup medium. The latter scenarios lead to a warm gas mass limit of M ≳ 4.5 × 109 M⊙.

We present analysis of the galaxy environment and physical properties of a partial Lyman limit system at z = 0.83718 with Hi and metal-line components closely separated in redshift space (vertical bar Delta v vertical bar approximate to 400 km s(-1)) towards the background quasar HE 1003 + 0149. The HST/COS far-ultraviolet spectrum provides coverage of lines of oxygen ions from OI to Ov. Comparison of observed spectral lines with synthetic profiles generated from Bayesian ionization modelling reveals the presence of two distinct gas phases in the absorbing medium. The low-ionization phase of the absorber has sub-solar metallicities (similar to 1/10 solar) with indications of [C/O] <0 in each of three components. The OIv and Ov trace a more diffuse higher ionization medium with predicted Hi column densities that are approximate to 2 dex lower. The quasar field observed with VLT/MUSE reveals three dwarf galaxies with stellar masses of M* similar to 10(8)-10(9) M-circle dot, and with star formation rates of approximate to 0.5-1 M-circle dot yr(-1), at projected separations of rho/R-vir approximate to 1.8-3.0 from the absorber. Over a wider field with projected proper separation of <= 5 Mpc and radial velocity offset of vertical bar Delta v vertical bar <= 1000 km s(-1) from the absorber, 21 more galaxies are identified in the VLT/VIMOS and Magellan deep galaxy redshift surveys, with 8 of them within 1 Mpc and 500 km s(-1), consistent with the line of sight penetrating a group of galaxies. The absorber presumably traces multiple phases of cool (T similar to 10(4) K) photoionized intragroup medium. The inferred [C/O] <0 hint at preferential enrichment from core-collapse supernovae, with such gas displaced from one or more of the nearby galaxies, and confined to the group medium.

We present a new method aimed at improving the efficiency of component by component ionization modeling of intervening quasar absorption line systems. We carry out cloud-by-cloud, multiphase modeling making use of CLOUDY and Bayesian methods to extract physical properties from an ensemble of absorption profiles. Here, as a demonstration of method, we focus on four weak, low ionization absorbers at low redshift, because they are multi-phase but relatively simple to constrain. We place errors on the inferred metallicities and ionization parameters for individual clouds, and show that the values differ from component to component across the absorption profile. Our method requires user input on the number of phases and relies on an optimized transition for each phase, one observed with high resolution and signal-to-noise. The measured Doppler parameter of the optimized transition provides a constraint on the Doppler parameter of HI, thus providing leverage in metallicity measurements even when hydrogen lines are saturated. We present several tests of our methodology, demonstrating that we can recover the input parameters from simulated profiles. We also consider how our model results are affected by which radiative transitions are covered by observations (for example how many HI transitions) and by uncertainties in the b parameters of optimized transitions. We discuss the successes and limitations of the method, and consider its potential for large statistical studies. This improved methodology will help to establish direct connections between the diverse properties derived from characterizing the absorbers and the multiple physical processes at play in the circumgalactic medium.

We present here results from a survey of intervening C iv absorbers at z < 0.16 conducted using 223 sightlines from the Hubble Spectroscopic Legacy Archive. Most systems (83%) out of the total sample of 69 have simple kinematics with 1 or 2 C iv components. In the 22 C iv systems with well constrained H i column densities, the temperatures from the b-values imply predominantly photoionized plasma (T ≤ 105K) and non-thermal dynamics. These systems also have solar or highermetallicities. We obtain a C iv line density of dN/dX = 5.1±1.0 for log[N (C iv) (cm−2)] ≥ 12.9, andΩC iv = (8.01±1.62)×10−8 for 12.9 ≤ log[N (C iv) (cm−2)] ≤ 15.0. The C iv bearing diffuse gas in the z < 0.16Universe has ametallicity of (2.07± 0.43) × 10−3 Z , an order of magnitude more than the metal abundances in the IGM at high redshifts (z & 5), and consistent with the slow build-up of metals in the diffuse circum/intergalactic space with cosmic time. For z < 0.015 (complete above L > 0.01L), the Sloan Digital Sky Survey provides a tentative evidence of declining covering fraction for strong C iv (N > 1013.5 cm−2) with ρ (impact parameter) and ρ/Rvir. However, the increase at high separations suggests that strong systems are not necessarily coincident with such galaxies. We also find that strong C iv absorption at z < 0.051 is not coincident with galaxy over-dense regions complete for L > 0.13L.

ABSTRACT We present the detection and analysis of a weak low-ionization absorber at z = 0.121 22 along the sightline of the blazar PG 1424+240, using spectroscopic data from both HST/COS and STIS. The absorber is a weak Mg ii analogue, with an incidence of weak C ii and Si ii, along with multicomponent C iv and O vi. The low ions are tracing a dense (nH ∼ 10−3 cm−3) parsec-scale cloud of solar or higher metallicity. The kinematically coincident higher ions are either from a more diffuse (nH ∼ 10−5–10−4 cm−3) photoionized phase of kiloparsec-scale dimensions or are tracing a warm (T ∼ 2 × 105 K) collisionally ionized transition temperature plasma layer. The absorber resides in a galaxy overdense region, with 18 luminous (>L*) galaxies within a projected radius of 5 Mpc and velocity of 750 km s−1. The multiphase properties, high metallicity, and proximity to a 1.4L* galaxy, at ρ ∼ 200 kpc and separation |Δv| = 11 km s−1, favour the possibility of the absorption tracing circumgalactic gas. The absorber serves as an example of weak Mg ii–O vi systems as a means to study multiphase high-velocity clouds in external galaxies.