arXiv subjects

P. Noterdaeme

Publications and source records attributed to P. Noterdaeme.

At least 19 recordsLinked to original sources

arXiv2026

HI 21-cm absorption in low- and high-excitation radio-loud AGNs at $z<0.5$ from MALS

We present results from a search of cold neutral gas associated with radio-loud active galactic nuclei (AGNs) at $z < 0.5$ using HI 21-cm absorption measurements from the MeerKAT Absorption Line Survey (MALS). Cross-matching the MALS 1006 MHz and SDSS DR18 catalogs yields 1908 radio sources at $z < 0.5$. Of these, 613 are classified as AGNs using BPT diagnostics and radio luminosity criteria. We further classify 426 AGNs into 327 low-excitation radio galaxies (LERGs) and 99 high-excitation radio galaxies (HERGs). We observe a significant ($>3\sigma$) difference in $k$-corrected $g-r$ color, consistent with LERGs residing in older galaxies with quenched star formation. We searched a radio-bright subsample of 79 LERGs and 20 HERGs ($S_{\mathrm{1.4\,GHz}} > 4$ mJy) for associated HI 21-cm absorption. This spans six decades in radio luminosity ($\log L_{\mathrm{1.4\,GHz}}$ (WHz$^{-1}$) $\sim 21.1-27.0$), probing an order of magnitude fainter than previous targeted HI surveys. We report five new detections (4 LERGs, 1 HERG) at $0.29 < z < 0.47$. The overall detection rate of $3^{+3}_{-2}$% (at a $3\sigma$ threshold of 10.0 kms$^{-1}$) is consistent with sensitivity-matched low-$z$ ($<0.2$) samples, suggesting no significant redshift evolution out to $z \sim 0.5$ or dependence on radio luminosity. Evaluating velocity offset, asymmetry, and width reveals three systems with entirely redshifted absorption and two with predominantly blueshifted absorption. HI profiles in LERGs show diverse asymmetries and velocity offsets exceeding 350 kms$^{-1}$, indicating disturbed cold-gas kinematics likely driven by lobe expansion or jet activity.

astro-ph.GA↗

arXiv2026

A z$\sim$1 galactic-scale outflow transversally mapped to $\sim$50 kpc through gravitational-arc tomography

We report spatially resolved measurements of cool gas traced by Mg II and Fe II absorption in the circumgalactic medium (CGM) of a star-forming galaxy at $z\sim1$ (G1). The fortuitous alignment of a background gravitational arc at z$\sim$2.4 provides seven closely spaced ($\sim$6 kpc) transverse sightlines along the minor axis of G1, probing its CGM out to $\sim$50 kpc. This geometry allows us to detect a galactic-scale outflow simultaneously in down-the-barrel and transverse directions, where blue-shifted Mg II absorption is detected along both types of sightlines, revealing a large-scale, collimated wind. We measure blue-shifted line-of-sight velocities of $v_{\mathrm{los}}$ $\sim$ 62 - 239 km s$^{-1}$ and line-of-sight velocity dispersions $\sigma_{\mathrm{los}}$ $\sim$ 53 - 133 km s$^{-1}$, suggesting a structure dominated by bulk motion. De-projection of $v_{\mathrm{los}}$ along the minor axis indicates that the outflow material barely approaches the escape velocity and is likely to be gravitationally bound to G1. We constrain an outflow opening angle $\theta_c\sim$ 18$^\circ$ - 25$^\circ$, and a mass outflow rate of $ \dot{M}_{\mathrm{out}}$ $\gtrsim$ 0.06 $M_\odot$ yr$^{-1}$, corresponding to a mass loading factor $\eta$ $\gtrsim$ 0.004, estimated within $\sim$10 - 50 kpc ($\sim$ 0.05 - 0.3 $R_\text{vir}$) of the galaxy centre. Our measurements, combined with previous arc tomography data along the major axis, indicate that normalizing impact parameters by galaxy B-band luminosity substantially reduces scatter in the established anti-correlation between Mg II equivalent width and impact parameter, while also diminishing possible excess of Mg II equivalent width towards the minor axis.

astro-ph.GA↗

arXiv2026

One H2 molecule per ten million H-atoms reveals sub-pc scale cold overdensities at z~4

We present the detection and analysis of H2 absorption at z = 4.24 towards the bright quasar J0007-5705, observed with the Very Large Telescope as part of the ESPRESSO QUasar Absorption Line Survey (EQUALS). The high resolving power, R~120000, enables the identification of extremely weak H2 lines in several rotational levels at a total column density of N(H2)~2x10^14 cm^-2, among the lowest ever measured in quasar absorption systems. Remarkably, this constitutes the highest-redshift H2 detection to date. Two velocity components are resolved, separated by only 3 km/s: a narrow (b~1.7 km/s) and a broader (b~6.2 km/s) component. Modelling the rotational population of H2 yields density of log nH/cm^-3 ~ 2.8 with temperature of ~40K (typical of the cold neutral medium) for the narrow component and log nH/cm^-3 ~ 1.4 , T~600K for the warmer, more turbulent component under a moderate ultraviolet (UV) field, suggesting at least several Mpc distance from the quasar. This system reveals the existence of tiny (down to ~0.01 pc), cold overdensities in the neutral medium. Their detection among only 7 damped Lyman-alpha systems in EQUALS suggests that they may be widespread yet usually remain undetected. H2 provides an exceptionally sensitive probe of these structures: even a minute molecular fraction produces measurable Lyman-Werner absorption lines along the extremely narrow optical beam -- the size of the quasar's accretion disc -- when observed at sufficiently high spectral resolution. High-resolution spectroscopy on extremely large telescopes may routinely detect and resolve such structures in the distant Universe, when 21-cm absorption will trace the collective contribution of many cold cloudlets toward larger radio background sources.

astro-ph.CO↗

arXiv2025

Origin of gas in the Magellanic Bridge: MeerKAT detection of HI 21-cm absorption

HI 21-cm absorption lines are investigated to determine the origin of the neutral atomic hydrogen (HI) of the Magellanic Bridge (MB). Using the MeerKat Absorption Line Survey (MALS) data we report the detection of an HI absorption line at a peak signal-to-noise ratio of 10 caused by MB gas against the radio source J033242.97-724904.5. In combination with earlier data obtained with the Australia Telescope Compact Array (ATCA) our new detected HI line permits the exploration of the MB atomic hydrogen gas across 4-6 kpc. The radial velocity profiles from the ATCA data and new data from MALS are analysed. Apart from the excitation conditions, the radial velocity structure of the HI gas seen in emission and absorption is investigated. Eventually the gas-to-dust ratio is quantified to identify the origin of the MB gas being either from the SMC (Small Magellanic Cloud) or the LMC (Large Magellanic Cloud). The HI absorption lines towards lines of sight separated by several kpc consistently coincide with the densest and perhaps coolest gas at the lower radial-velocity limit of the corresponding HI emission profiles. The gas-to-dust ratio is found to be consistent with an origin of the MB gas from the LMC. The large scale velocity distribution as seen from the HI absorption features favors the LMC-SMC direct collision scenario over the close fly-by scenario, as also currently found by numerical simulations.

astro-ph.GA↗

arXiv2025

The MeerKAT Absorption Line Survey (MALS) data release 3: Cold atomic gas associated with the Milky Way

We present results of a blind search for Galactic HI 21-cm absorption lines toward 19130 radio sources, using 390 pointings of MALS, each pointing centered on a source brighter than 200 mJy. We detected 3640 HI absorption features. This represents the largest Galactic HI absorption line catalog to date. Based on the strong correlation between the HI 21-cm emission line column densities ($N_{HI}$) and the visual extinction ($A_V$) measured toward the pointing center, along with the confinement of the absorption features to a narrow range in radial velocities (-25$ 2\sigma$. A similar difference is observed for H$_2$ detections and non-detections in damped Lyman-alpha systems at $z$ > 1.8, implying that turbulence-driven WNM-to-CNM conversion is the common governing factor for the presence of HI 21-cm and H$_2$ absorption. Through a comparison of central and off-axis absorption features, we find that the slope of rms fluctuations in the optical depth variations in the quiescent gas associated with LISM is shallower than the earlier measurements in the disk. The densities (20-30 cm$^{-3}$) inferred from the optical depth variations are typical of the CNM values. The negligible velocity shifts between central and off-axis absorbers are in line with the hypothesis that the CNM and LNM clouds freeze out of the extended WNM phase.

astro-ph.GA↗

arXiv2025

Exploring quasar evolution with proximate molecular absorbers: Insights from the kinematics of highly ionized nitrogen

We investigate the presence and kinematics of NV absorption proximate to high redshift quasars selected upon the presence of strong $H_{2}$ and HI absorption at the quasar redshift. Our spectroscopic observations with X-shooter at the VLT reveal a 70% detection rate of NV (9 of 13 quasars with 2.5 < z < 3.3), remarkably higher than the 10% detection rate in intervening DLA systems and the 30% rate observed within a few thousand km/s of the source in the general quasar population. While many NV components lie within the velocity range of the neutral gas, the kinematic profiles of high-ionization species appear decoupled from those of low-ionization species, with the former extending over much larger velocity ranges, particularly towards bluer velocities. We also observe significant variations in the NV/SiIV, which we attribute to varying ionization conditions, with a velocity-dependent trend: blueshifted NV components systematically exhibit higher ionization parameters compared to those near the quasar's systemic redshift. Furthermore, the most redshifted systems relative to the quasar show no evidence of NV absorption. The results suggest that proximate $H_{2}$ absorption systems select critical stages of quasar evolution, during which the quasar remains embedded in a rich molecular environment. Redshifted systems trace infalling gas, potentially associated with mergers, preceding the onset of outflows. Such outflows may reach or even carry out neutral and molecular gas.This latter stage would correspond to proximate $H_{2}$ systems located around or blueshifted relative to the quasar's systemic z. Finally, the only case in our sample featuring highly blueshifted neutral gas shows no evidence of an association with the quasar.Our findings highlight the need to account for the ionization state when defining a velocity threshold to distinguish quasar-associated systems from intervening.

astro-ph.GA↗

arXiv2024

Modelling of long gamma-ray burst host galaxies at cosmic noon from damped Lyman-{\alpha} absorption statistics

We study the properties of long gamma-ray burst (GRB) host galaxies using a statistical modelling framework derived to model damped Lyman-$\alpha$ absorbers (DLAs) in quasar spectra at high redshift. The distribution of NHI for GRB-DLAs is $\sim$10 times higher than what is found for quasar-DLAs at similar impact parameters. We interpret this as a temporal selection effect due to the short-lived GRB progenitor probing its host at the onset of a starburst where the interstellar medium may exhibit multiple overdense regions. Owing to the larger NHI, the dust extinction is larger with 29 per cent of GRB-DLAs exhibiting A(V)>1 mag in agreement with the fraction of 'dark bursts'. Despite the differences in NHI distributions, we find that high-redshift 2 < z < 3 quasar- and GRB-DLAs trace the luminosity function of star-forming host galaxies in the same way. We propose that their differences may arise from the fact that the galaxies are sampled at different times in their star formation histories, and that the absorption sightlines probe the galaxy haloes differently. Quasar-DLAs sample the full H I cross-section, whereas GRB-DLAs sample only regions hosting cold neutral medium. Previous studies have found that GRBs avoid high-metallicity galaxies ($\sim$0.5 $Z_{\odot}$). Since at these redshifts galaxies on average have lower metallicities, our sample is only weakly sensitive to such a threshold. Lastly, we find that the modest detection rate of cold gas (H$_2$ or C I) in GRB spectra can be explained mainly by a low volume filling factor of cold gas clouds and to a lesser degree by destruction from the GRB explosion itself.

astro-ph.GA↗

arXiv2024

Transverse clues on the kpc-scale structure of the circumgalactic medium as traced by C IV absorption

We present VLT/MUSE integral-field spectroscopy ($R\approx 1\,800$) of four giant gravitational arcs exhibiting strong C IV absorption at 8 intervening redshifts, $z_{abs}\approx 2.0$--$2.5$. We detect C IV absorption in a total of 222 adjacent and seeing-uncorrelated sightlines, whose spectra sample beams of ("de-lensed") linear size $\approx 1$ kpc. Our data show that (1) absorption velocities cluster at all probed transverse scales, $\Delta r_\perp\approx0$--$15$ kpc, depending on system; (2) the (transverse) velocity dispersion never exceeds the mean (line-of-sight) absorption spread; and (3) the (transverse) velocity autocorrelation function does not resolve kinematic patterns at the above spatial scales, but its velocity projection, $\xi^{arc}(\Delta v)$, exhibits a similar shape to the known two-point correlation function toward quasars, $\xi^{QSO}(\Delta v)$. An empirical kinematic model suggests that these results are a natural consequence of wide-beam observations of an unresolved clumpy medium. Our model recovers both the underlying velocity dispersion of the clumps ($70$--$170$ \kms) and the mean number of clumps per unit area ($2$--$13$ kpc$^{-2}$). The latter constrains the projected mean inter-clump distance to within $\approx0.3$--$0.8$ kpc, which we argue is a measure of clump size for near-unity covering fraction. The model is also able to predict $\xi^{arc}(\Delta v)$ from $\xi^{QSO}(\Delta v)$, suggesting that the strong systems that shape the former and the line-of-sight velocity components that define the latter trace the same kinematic population. Consequently, the clumps must possess an internal density structure that generates both weak and strong components. We discuss how our interpretation is consistent with previous observations using background galaxies and multiple quasars.

astro-ph.GA↗

arXiv2024

The rich galactic environment of a H$_2$-absorption selected quasar

We present the first VLT/MUSE observations of a quasar featuring a proximate molecular absorption system, SDSS J125917.31+030922.5. The proximate damped Ly$\alpha$ absorption acts as a natural coronagraph, removing the quasar emission over $\sim$40 {\AA} in wavelength, and allows us to detect extended Ly$\alpha$ emission without the necessity of subtracting the quasar emission. This natural coronagraph permits the investigation of the quasar environment down to its inner regions ($r < 20$ kpc), where galaxy interactions or feedback processes should have the most noticeable effects. Our observations reveal a dense environment, with a highly asymmetric Ly$\alpha$ emission within $2"$ ($\sim 15$ kpc), possibly shaped by a companion galaxy, and a southern extension of the nebulae at about 50~kpc, with rotation-like kinematic signature. The width of the Ly$\alpha$ emission is broadest closer to the quasar, indicating perturbed kinematics as expected if interactions and significant gas flows are present. The foreground absorbing system itself is redshifted by $\approx $400 km/s relative to the background quasar, and therefore is likely arising from gas moving towards the quasar. Finally two additional Ly$\alpha$ emitters are detected with $>10\,\sigma$ significance at 96 and 223 kpc from the quasar, making this field overdense relative to other similar observations of quasars at $z\sim 3$. Our results support the hypothesis that quasars with proximate neutral/molecular absorption trace rich environments where galaxy interactions are at play and motivates further studies of H$_2$-selected quasars to shed light on feeding and feedback processes.

astro-ph.GA↗

arXiv2024

A New Precise Determination of the Primordial Abundance of Deuterium: Measurement in the metal-poor sub-DLA system at z=3.42 towards quasar J1332+0052

The theory of Big Bang nucleosynthesis, coupled with an estimate of the primordial deuterium abundance (D/H)_pr, offers insights into the baryon density of the Universe. Independently, the baryon density can be constrained during a different cosmological era through the analysis of cosmic microwave background (CMB) anisotropy. The comparison of these estimates serves as a rigorous test for the self-consistency of the Standard Cosmological Model and stands as a potent tool in the quest for new physics beyond the Standard Model of Particle Physics. For a meaningful comparison, a clear understanding of the various systematic errors affecting deuterium measurements is crucial. Given the limited number of D/H measurements, each new estimate carries significant weight. This study presents the detection of DI absorption lines in a metal-poor sub-Damped Lyman-alpha system ([O/H]=-1.71+-0.02, logN(HI)=19.304+-0.004) at z_abs=3.42 towards the quasar J1332+0052. Through simultaneous fitting of HI and DI Lyman-series lines, as well as low-ionization metal lines, observed at high spectral resolution and high signal-to-noise using VLT/UVES and Keck/HIRES, we derive log(DI/HI)=-4.622+-0.014, accounting for statistical and systematic uncertainties of 0.008dex and 0.012dex, respectively. Thanks to negligible ionization corrections and minimal deuterium astration at low metallicity, this D/H ratio provides a robust measurement of the primordial deuterium abundance, consistent and competitive with previous works. Incorporating all prior measurements, the best estimate of the primordial deuterium abundance is constrained as: (D/H)_pr=(2.533+-0.024)*10^-5. This represents a 5% improvement in precision over previous studies and reveals a moderate tension with the expectation from the Standard Model (~2.2sig). This discrepancy underscores the importance of further measurements in the pursuit of new physics.

astro-ph.CO↗

arXiv2023

Cosmology and fundamental physics with the ELT-ANDES spectrograph

State-of-the-art 19th century spectroscopy led to the discovery of quantum mechanics, and 20th century spectroscopy led to the confirmation of quantum electrodynamics. State-of-the-art 21st century astrophysical spectrographs, especially ANDES at ESO's ELT, have another opportunity to play a key role in the search for, and characterization of, the new physics which is known to be out there, waiting to be discovered. We rely on detailed simulations and forecast techniques to discuss four important examples of this point: big bang nucleosynthesis, the evolution of the cosmic microwave background temperature, tests of the universality of physical laws, and a real-time model-independent mapping of the expansion history of the universe (also known as the redshift drift). The last two are among the flagship science drivers for the ELT. We also highlight what is required for the ESO community to be able to play a meaningful role in 2030s fundamental cosmology and show that, even if ANDES only provides null results, such `minimum guaranteed science' will be in the form of constraints on key cosmological paradigms: these are independent from, and can be competitive with, those obtained from traditional cosmological probes.

astro-ph.CO↗

arXiv2023

MALS discovery of a rare HI 21-cm absorber at $z\sim1.35$: origin of the absorbing gas in powerful AGN

We report a new, rare detection of HI 21-cm absorption associated with a quasar (only six known at $1 5$ GHz). The simplest explanation would be that no large HI column (N(HI)$>10^{17}$ cm$^{-2}$) is present towards the radio `core' and the optical AGN. Based on the joint optical and radio analysis of a heterogeneous sample of 16 quasars ($z_{median}$ = 0.7) and 15 radio galaxies ($z_{median}$ = 0.3) with HI 21-cm absorption detection and matched in 1.4 GHz luminosity (L$_{\rm 1.4\,GHz}$), a consistent picture emerges where quasars are primarily tracing the gas in the inner circumnuclear disk and cocoon created by the jet-ISM interaction. These exhibit L$_{1.4\,\rm GHz}$ - $\Delta V_{\rm null}$ correlation, and frequent mismatch between the radio and optical spectral lines. The radio galaxies show no such correlation and likely trace the gas from the cocoon and the galaxy-wide ISM outside the photoionization cone. The analysis presented here demonstrates the potential of radio spectroscopic observations to reveal the origin of the absorbing gas associated with AGN that may be missed in optical observations.

astro-ph.GA↗

arXiv2023

Directly constraining the spatial coherence of the $z\sim1$ circumgalactic medium

One of the biggest puzzles regarding the circumgalactic medium (CGM) is the structure of its cool ($T\sim10^4$ K) gas phase. While the kinematics of quasar absorption systems suggests the CGM is composed of a population of different clouds, constraining the clouds' extent and spatial distribution has proven challenging, both from the theoretical and observational points of view. In this work we study the spatial structure of the $z\sim 1$ CGM with unprecedented detail via resolved spectroscopy of giant gravitational arcs. We put together a sample of Mg II$\lambda\lambda 2796,2803$ detections obtained with VLT/MUSE in 91 spatially independent and contiguous sight-lines toward 3 arcs, each probing an isolated star-forming galaxy believed to be detected in absorption. We constrain the coherence scale of this gas ($C_{\rm{length}}$), which represents the spatial scale over which the Mg II equivalent width (EW) remains constant, by comparing EW variations measured across all sight-lines with empirical models. We find $1.4 <C_{\rm{length}}/\rm{kpc} <7.8$ (95% confidence). This measurement, of unprecedented accuracy, represents the scale over which the cool gas tends to cluster in separate structures. We argue that, if $C_{\rm{length}}$ is a universal property of the CGM, it needs to be reproduced by current and future theoretical models in order to understand the exact role of this medium in galaxy evolution.

astro-ph.GA↗

arXiv2023

The MeerKAT Absorption Line Survey (MALS) data release I: Stokes I image catalogs at 1-1.4 GHz

The MeerKAT Absorption Line Survey (MALS) has observed 391 telescope pointings at L-band (900 - 1670 MHz) at $\delta\lesssim$ $+20\deg$. We present radio continuum images and a catalog of 495,325 (240,321) radio sources detected at a signal-to-noise ratio (SNR) $>$5 over an area of 2289 deg$^2$ (1132 deg$^2$) at 1006 MHz (1381 MHz). Every MALS pointing contains a central bright radio source ($S_{1\,\mathrm{GHz}} \gtrsim 0.2$ Jy). The median spatial resolution is $12^{\prime\prime}$ ($8^{\prime\prime}$). The median rms noise away from the pointing center is 25 $\mu$Jy beam$^{-1}$ (22 $\mu$Jy beam$^{-1}$) and is within $\sim$ 15% of the achievable theoretical sensitivity. The flux density scale ratio and astrometric accuracy deduced from multiply observed sources in MALS are less than 1% (8% scatter) and $1^{\prime\prime}$, respectively. Through comparisons with NVSS and FIRST at 1.4 GHz, we establish the catalog's accuracy in the flux density scale and astrometry to be better than 6% (15% scatter) and $0.8^{\prime\prime}$, respectively. The median flux density offset is higher (9%) for an alternate beam model based on holographic measurements. The MALS radio source counts at 1.4 GHz are in agreement with literature. We estimate spectral indices ($\alpha$) of a subset of 125,621 sources (SNR$>$8), confirm the flattening of spectral indices with decreasing flux density and identify 140 ultra steep-spectrum ($\alpha<-1.3$) sources as prospective high-$z$ radio galaxies ($z>2$). We have identified 1308 variable and 122 transient radio sources comprising primarily of AGN that demonstrate long-term (26 years) variability in their observed flux densities. The MALS catalogs and images are publicly available at https://mals.iucaa.in.

astro-ph.GA↗

arXiv2023

Proximate molecular quasar absorbers: Chemical enrichment and kinematics of the neutral gas

Proximate molecular quasar absorbers (PH2) are an intriguing population of absorption systems recently uncovered through strong H2 absorption at small velocity separation from the background quasars. We performed a multi-wavelength spectroscopic follow-up of thirteen such systems with VLT/X-Shooter. Here, we present the observations and study the overall chemical enrichment measured from the HI, H2 and metal lines. We combine this with an investigation of the neutral gas kinematics with respect to the quasar host. We find gas-phase metallicities in the range 2% to 40% of the Solar value, i.e. in the upper-half range of HI-selected proximate damped Lyman-alpha systems, but similar to what is seen in intervening H2-bearing systems. This is likely driven by similar selection effects that play against the detection of most metal and molecular rich systems in absorption. Differences are however seen in the abundance of dust (from [Zn/Fe]) and its depletion pattern, when compared to intervening systems, possibly indicating different dust production or destruction close to the AGN. We also note the almost-ubiquitous presence of a high-ionisation phase traced by NV in proximate systems. In spite of the hard UV field from the quasars, we found no strong overall deficit of neutral argon, at least when compared to intervening DLAs. This likely results from argon being mostly neutral in the H2 phase, which actually accounts for a large fraction of the total amount of metals. We measure the quasar systemic redshifts through emission lines from both ionised gas and CO(3-2) emission, the latter being detected in all 6 cases for which we obtained 3-mm data from complementary NOEMA observations. For the first time, we observe a trend between line-of-sight velocity with respect to systemic redshift and metallicity of the absorbing gas. [truncated]

astro-ph.GA↗

arXiv2022

CUBES: a UV spectrograph for the future

In spite of the advent of extremely large telescopes in the UV/optical/NIR range, the current generation of 8-10m facilities is likely to remain competitive at ground-UV wavelengths for the foreseeable future. The Cassegrain U-Band Efficient Spectrograph (CUBES) has been designed to provide high-efficiency (>40%) observations in the near UV (305-400 nm requirement, 300-420 nm goal) at a spectral resolving power of R>20,000, although a lower-resolution, sky-limited mode of R ~ 7,000 is also planned. CUBES will offer new possibilities in many fields of astrophysics, providing access to key lines of stellar spectra: a tremendous diversity of iron-peak and heavy elements, lighter elements (in particular Beryllium) and light-element molecules (CO, CN, OH), as well as Balmer lines and the Balmer jump (particularly important for young stellar objects). The UV range is also critical in extragalactic studies: the circumgalactic medium of distant galaxies, the contribution of different types of sources to the cosmic UV background, the measurement of H2 and primordial Deuterium in a regime of relatively transparent intergalactic medium, and follow-up of explosive transients. The CUBES project completed a Phase A conceptual design in June 2021 and has now entered the Phase B dedicated to detailed design and construction. First science operations are planned for 2028. In this paper, we briefly describe the CUBES project development and goals, the main science cases, the instrument design and the project organization and management.

astro-ph.IM↗

arXiv2022

PKS1413+135: OH and HI at z = 0.247 with MeerKAT

The BL Lac PKS 1413+135 was observed by the Large Survey Project "MeerKAT Absorption Line Survey" (MALS) in the L-band, at 1139 MHz and 1293-1379 MHz, targeting the HI and OH lines in absorption at z = 0.24671. The radio continuum is thought to come from a background object at redshift lower than 0.5, as suggested by the absence of gravitational images. The HI absorption line is detected at high signal-to-noise, with a narrow central component, and a red wing, confirming previous results. The OH 1720 MHz line is clearly detected in (maser) emission, peaking at a velocity shifted by -10 to -15 km/s with respect to the HI peak. The 1612 MHz line is lost due to radio interferences. The OH 1667 MHz main line is tentatively detected in absorption, but not the 1665 MHz one. Over 30 years, a high variability is observed in optical depths, due to the rapid changes of the line of sight, caused by the superluminal motions of the radio knots. The HI line has varied by 20 per cent in depth, while the OH-1720 MHz depth has varied by a factor 4. The position of the central velocity and the widths also varied. The absorbing galaxy is an early-type spiral (maybe S0) seen edge-on, with a prominent dust lane, covering the whole disk. Given the measured mass concentration, and the radio continuum size at centimeter wavelengths (100 mas corresponding to 400 pc at z = 0.25), the width of absorption lines from the nuclear regions are expected up to 250 km/S. The narrowness of the observed lines (< 15 km/s) suggest that the absorption comes from an outer gas ring, as frequently observed in S0 galaxies. The millimetric lines are even narrower (< 1 km/s), which corresponds to the continuum size restricted to the core. The core source is covered by individual 1 pc molecular clouds, of column density a few 10^22 cm-2, which is compatible with the gas screen detected in X-rays.

astro-ph.GA↗

arXiv2022

Orientation effects on cool gas absorption from gravitational-arc tomography of a z = 0.77 disc galaxy

We use spatially-resolved spectroscopy of a distant giant gravitational arc to test orientation effects on MgII absorption equivalent width (EW) and covering fraction (kappa) in the circumgalactic medium of a foreground star-forming galaxy (G1) at z~0.77. Forty-two spatially-binned arc positions uniformly sample impact parameters (D) to G1 between 10 and 30 kpc and azimuthal angles alpha between 30 and 90 degrees (minor axis). We find an EW-D anti-correlation, akin to that observed statistically in quasar absorber studies, and an apparent correlation of both EW and kappa with alpha, revealing a non-isotropic gas distribution. In line with our previous results on MgII kinematics suggesting the presence of outflows in G1, at minimum a simple 3-D static double-cone model (to represent the trace of bipolar outflows) is required to recreate the EW spatial distribution. The D and alpha values probed by the arc cannot confirm the presence of a disc, but the data highly disfavor a disc alone. Our results support the interpretation that the EW-alpha correlation observed statistically using other extant probes is partly shaped by bipolar metal-rich winds.

astro-ph.GA↗