This paper investigates C iv absorption in the circumgalactic medium (CGM) of L-star galaxies and its relationship with galaxy star formation rates. We present new observations from the C iv in L-star galaxies survey (PID#17076) using the Hubble Space Telescope/Cosmic Origins Spectrograph. By combining these measurements with archival C iv data (46 observations total), we estimate detection fractions for star-forming (sSFR > 10(-11) yr(-1)) and passive galaxies (sSFR <= 10(-11) yr(-1) ) to be 72(-18)(+14)% [21/29] and 23(-15)(+27)% [3/13], respectively. This indicates a significant dichotomy in C iv presence between L-star star-forming and passive galaxies, with over 99% confidence. This finding aligns with J. Tumlinson et al., which noted a similar dichotomy in O vi absorption. Our results imply a substantial carbon reservoir in the CGM of L star galaxies, suggesting a minimum carbon mass of greater than or similar to 3.03 x 10(6) M-circle dot out to 120 kpc. Together, these findings highlight a strong connection between star formation in galaxies and the state of their CGM, providing insight into the mechanisms governing galaxy evolution.

H I-rich absorbers seen within quasar spectra contain the bulk of neutral gas in the Universe. However, the spatial extent of these reservoirs are not extensively studied due to the pencil beam nature of quasar sightlines. Using two giant gravitational arc fields (at redshifts 1.17 and 2.06) as 2D background sources with known strong Mg II absorption observed with the Multi Unit Spectroscopic Explorer integral field spectrograph (IFS), we investigated whether spatially mapped Mg II absorption can predict the presence of strong H I systems, and determine both the physical extent and H I mass of the two absorbing systems. We created a simple model of an ensemble of gas clouds in order to simultaneously predict the H I column density and gas covering fraction of H I-rich absorbers based on observations of the Mg II rest-frame equivalent width in IFS spaxels. We first test the model on the lensing field with H I observations already available from the literature, finding that we can recover H I column densities consistent with the previous estimates (although with large uncertainties). We then use our framework to simultaneously predict the gas covering fraction, H I column density and total H I gas mass (M-HI) for both fields. We find that both of the observed strong systems have a covering fraction of approximate to 70% and are likely damped Lyman alpha systems (DLAs) with MHI > 109 M-circle dot. Our model shows that the typical Mg II metrics used in the literature to identify the presence of DLAs are sensitive to the gas covering fraction. However, these Mg II metrics are still sensitive to strong H I, and can be still applied to absorbers towards gravitational arcs or other spatially extended background sources. Based on our results, we speculate that the two strong absorbers are likely representative of a neutral inner circumgalactic medium and are a significant reservoir of fuel for star formation within the host galaxies.

In the pursuit of understanding the multiplicity of massive stars, the OWN Survey has undertaken spectroscopic monitoring of hundreds of targets over the past 20 yr. This effort has led to the discovery of new single-lined spectroscopic binaries. Characterizing the unseen companions of these systems is crucial to deriving precise stellar parameters, including the mass of each component, and constraining formation models for massive binary systems. In this paper, we aim to physically and evolutionarily characterize the stellar components of the massive binary HD 165246. We analyzed spectra obtained by the OWN Survey and used Kepler's second mission (K2) photometry, from which we determined the physical parameters of the system. Thanks to the high-resolution capabilities of the new echelle spectrograph Gemini/GHOST, we could directly detect spectral features of the secondary component for the first time. A very low mass ratio for the system is confirmed ( q ~ 0.16), making this binary one of the few extremely low mass ratio systems known. The primary star has a mass of M a = 22 ± 1 M ⊙ and a radius of R a = 7.0 ± 0.1 R ⊙ , while the secondary star has a mass of M b = 3.4 ± 0.1 M ⊙ and a radius of R b = 2.22 ± 0.02 R ⊙ . Stellar evolution models indicate that the system has undergone approximately two million years of evolution since its formation. Moreover, the secondary star is identified as a pre-main-sequence object, progressing toward the zero-age main sequence. This paper illustrates the power of high-resolution spectrographs such as GHOST in finding much lower mass, previously unseen stellar components of binary star systems.

This paper investigates C IV absorption in the circumgalactic medium (CGM) of L* galaxies and its relationship with galaxy star formation rates. We present new observations from the C IV in L* survey (CIViL*; PID#17076) using the Hubble Space Telescope/Cosmic Origins Spectrograph. By combining these measurements with archival C IV data (46 observations total), we estimate detection fractions for star-forming (sSFR > 10^-11 yr^-1) and passive galaxies (sSFR ≤ 10^-11 yr^-1) to be 72_-18^+14% [21/29] and 23_-15^+27% [3/13], respectively. This indicates a significant dichotomy in C IV presence between L* star-forming and passive galaxies, with over 99 (2011), which noted a similar dichotomy in O VI absorption. Our results imply a substantial carbon reservoir in the CGM of L* galaxies, suggesting a minimum carbon mass of ≳ 3.03 × 10^6 M_⊙ out to 120 kpc. Together, these findings highlight a strong connection between star formation in galaxies and the state of their CGM, providing insight into the mechanisms governing galaxy evolution.

We present VLT/MUSE integral-field spectroscopy (R≈ 1 800) of four giant gravitational arcs exhibiting strong C IV absorption at 8 intervening redshifts, z_abs≈ 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 ≈ 1 kpc. Our data show that (1) absorption velocities cluster at all probed transverse scales, Δ r_⊥≈0–15 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, ξ^arc(Δ v), exhibits a similar shape to the known two-point correlation function toward quasars, ξ^QSO(Δ 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 ) and the mean number of clumps per unit area (2–13 kpc^-2). The latter constrains the projected mean inter-clump distance to within ≈0.3–0.8 kpc, which we argue is a measure of clump size for near-unity covering fraction. The model is also able to predict ξ^arc(Δ v) from ξ^QSO(Δ 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.

With high equilibrium temperatures and tidally locked rotation, ultra-hot Jupiters (UHJs) are unique laboratories within which to probe extreme atmospheric physics and chemistry. In this paper, we present high-resolution dayside spectroscopy of the UHJ WASP-189 b obtained with the new Gemini High-resolution Optical SpecTrograph (GHOST) at the Gemini South Observatory. The observations, which cover 3 hr of post-eclipse orbital phases, were obtained during the instrument’s System Verification run. We detect the planet’s atmosphere via the Doppler cross-correlation technique, and recover a detection of neutral iron in the planet’s dayside atmosphere at a significance of 7.5 σ in the red arm of the data, verifying the presence of a thermal inversion. We also investigate the presence of other species in the atmosphere and discuss the implications of model injection/recovery tests. These results represent the first atmospheric characterization of an exoplanet with GHOST’s high-resolution mode, and demonstrate the potential of this new instrument in detecting and studying ultra-hot exoplanet atmospheres.

We present the first Very Large Telescope (VLT) Multi Unit Spectroscopic Explorer (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 similar to 40 & Aring; 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 '' (similar to 15 kpc), possibly shaped by a companion galaxy, and a southern extension of the nebulae to 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 approximate to 400 km/s relative to the background quasar, and therefore is likely arising from gas moving toward 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 similar to 3. Our results support the hypothesis that quasars with proximate neutral and 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.

We present the first VLT/MUSE observations of a quasar featuring a proximate molecular absorption system, SDSS J125917.31+030922.5. The proximate damped Lyα absorption acts as a natural coronagraph, removing the quasar emission over ∼40 Å in wavelength, and allows us to detect extended Lyα 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 Lyα emission within 2" (∼ 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 Lyα 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 ≈400 km/s relative to the background quasar, and therefore is likely arising from gas moving towards the quasar. Finally two additional Lyα emitters are detected with >10 σ significance at 96 and 223 kpc from the quasar, making this field overdense relative to other similar observations of quasars at z∼ 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.

The Gemini High-resolution Optical SpecTrograph (GHOST) is a new echelle spectrograph available on the Gemini-South telescope as of Semester 2024A. We present the first high resolution spectrum of the quasar J1449-1227 (redshift z_em=3.27) using data taken during the commissioning of GHOST. The observed quasar hosts an intervening iron-poor ([Fe/H] = -2.5) damped Lyman alpha (DLA) system at redshift z=2.904. Taking advantage of the high spectral resolving power of GHOST (R~55000), we are able to accurately model the metal absorption lines of the metal-poor DLA and find a supersolar [Si/Fe], suggesting the DLA gas is in an early stage of chemical enrichment. Using simple ionization models, we find that the large range in the C IV/Si IV column density ratio of individual components within the DLA's high ionization absorption profile can be reproduced by several metal-poor Lyman limit systems surrounding the low-ionization gas of the DLA. It is possible that this metal-poor DLA resides within a complex system of metal-poor galaxies or filaments with inflowing gas. The high spectral resolution, wavelength coverage and sensitivity of GHOST makes it an ideal spectrograph for characterizing the chemistry and kinematics of quasar absorption lines.

The kiloparsec-scale kinematics and density structure of the circumgalactic medium (CGM) is still poorly constrained observationally, which poses a problem for understanding the role of the baryon cycle in galaxy evolution. Here we present VLT/MUSE integral-field spectroscopy (R approximate to 1800) of four giant gravitational arcs exhibiting W-0 greater than or similar to 0.2 & Aring; C IV absorption at eight intervening redshifts, z(abs) approximate to 2.0-2.5. We detected C IV absorption in a total of 222 adjacent and seeing-uncorrelated sight lines whose spectra sample beams of ("de-lensed") linear size approximate to 1 kpc. Our data show that (1) absorption velocities cluster at all probed transverse scales, Delta r(perpendicular to) approximate to 0-15 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 km s(-1)) and the mean number of clumps per unit area (2-13 kpc(-2)). The latter constrains the projected mean inter-clump distance to within approximate to 0.3-0.8 kpc, which we argue is a measure of clump size for a 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 xi(arc)(Delta v) and the line-of-sight velocity components that define xi(QSO)(Delta v) 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 as well as its implications for the connection between the small-scale kinematic structure of the CGM and galactic-scale accretion and feedback processes.

This study focuses on Pristine_180956.78-294759.8 (hereafter P180956, [Fe/H] = -1.95 +/- 0.02), a star selected from the Pristine Inner Galaxy Survey (PIGS), and followed-up with the recently commissioned Gemini High-resolution Optical SpecTrograph (GHOST) at the Gemini South telescope. The GHOST spectrograph's high efficiency in the blue spectral region (3700-4800 & Aring;) enables the detection of elemental tracers of early supernovae (e.g. Al, Mn, Sr, and Eu). The star exhibits chemical signatures resembling those found in ultrafaint dwarf (UFD) systems, characterized by very low abundances of neutron-capture elements (Sr, Ba, and Eu), which are uncommon among stars in the Milky Way halo. Our analysis suggests that P180956 bears the chemical imprints of a small number (2 or 4) of low-mass hypernovae (similar to 10-15M(circle dot)), which are needed to mostly reproduce the abundance pattern of the light-elements (e.g. [Si, Ti/Mg, Ca] similar to 0.6), and one fast-rotating intermediate-mass supernova (similar to 300km s(-1), similar to 80-120M(circle dot)), which is the main channel contributing to the high [Sr/Ba] (similar to+1.2). The small pericentric (similar to 0.7kpc) and apocentric (similar to 13kpc) distances and its orbit confined to the plane (less than or similar to 2kpc) indicate that this star was likely accreted during the early Galactic assembly phase. Its chemo-dynamical properties suggest that P180956 formed in a system similar to a UFD galaxy accreted either alone, as one of the low-mass building blocks of the proto-Galaxy, or as a satellite of Gaia-Sausage-Enceladus. The combination of Gemini's large aperture with GHOST's high efficiency and broad spectral coverage makes this new spectrograph one of the leading instruments for near-field cosmology investigations.

The Gemini High Resolution Optical Spectrograph (GHOST) is a fiber-fed spectrograph system on the Gemini South telescope that provides simultaneous wavelength coverage from 348 - 1061nm, and designed for optimal performance between 363 - 950nm. It can observe up to two objects simultaneously in a 7.5 arcmin diameter field of regard at R = 56,000 or a single object at R = 75,000. The spectral resolution modes are obtained by using integral field units to image slice a 1.2" aperture by a factor of five in width using 19 fibers in the high resolution mode and by a factor of three in width using 7 fibers in the standard resolution mode. GHOST is equipped with hardware to allow for precision radial velocity measurements, expected to approach meters per second precision. Here, we describe the basic design and operational capabilities of GHOST, and proceed to derive and quantify the key aspects of its on-sky performance that are of most relevance to its science users.

The Gemini South telescope is now equipped with a new high-resolution spectrograph called the Gemini High-resolution Optical SpecTrograph (GHOST). This instrument provides high-efficiency, high-resolution spectra covering 347-1060 nm in a single exposure of either one or two targets simultaneously, along with precision radial velocity spectroscopy utilizing an internal calibration source. It can operate at a spectral element resolving power of either 76,000 or 56,000, and can reach a signal-to-noise ratio of similar to 5 in a 1 hr exposure on a V similar to 20.8 mag target in median site seeing and dark skies (per resolution element). GHOST was installed on-site in 2022 June, and we report performance after full integration to queue operations in 2023 November, in addition to scientific results enabled by the integration observing runs. These results demonstrate the ability to observe a wide variety of bright and faint targets with high efficiency and precision. With GHOST, new avenues to explore high-resolution spectroscopy have opened up to the astronomical community. These are described, along with the planned and potential upgrades to the instrument.

We present two new tools for studying and modelling metal absorption lines in the circumgalactic medium. The first tool, dubbed 'NMF Profile Maker' (NMF-PM), uses a non-negative matrix factorization (NMF) method and provides a robust means to generate large libraries of realistic metal absorption profiles. The method is trained and tested on 650 unsaturated metal absorbers in the redshift interval z = 0.9-4.2 with column densities in the range of 11.2 <= log (N/cm(-2)) <= 16.3, obtained from high-resolution (R > 4000) and high-signal-to-noise ratio (S/N >= 10) quasar spectroscopy. To avoid spurious features, we train on infinite S/N Voigt models of the observed line profiles derived using the code 'Monte-Carlo Absorption Line Fitter' (MC-ALF), a novel automatic Bayesian fitting code that is the second tool we present in this work. MC-ALF is a Monte-Carlo code based on nested sampling that, without the need for any prior guess or human intervention, can decompose metal lines into individual Voigt components. Both MC-ALF and NMF-PM are made publicly available to allow the community to produce large libraries of synthetic metal profiles and to reconstruct Voigt models of absorption lines in an automatic fashion. Both tools contribute to the scientific effort of simulating and analysing metal absorbers in very large spectroscopic surveys of quasars like the ongoing Dark Energy Spectroscopic Instrument, the 4-m Multi-Object Spectroscopic Telescope, and the WHT Enhanced Area Velocity Explorer surveys.

One of the biggest puzzles regarding the circumgalactic medium (CGM) is the structure of its cool ( T ∼ 10 4 K) gas phase. While the kinematics of quasar absorption systems suggests the CGM is composed of a population of different clouds, constraining their extent and spatial distribution has proven challenging, both from theoretical and observational points of view. In this work, we study the spatial structure of the z ∼ 1 CGM with unprecedented detail via resolved spectroscopy of giant gravitational arcs. We put together a sample of Mg II λλ 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 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 length /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 length is a universal property of the CGM, it needs to be reproduced by current and future theoretical models in order for us to understand the exact role of this medium in galaxy evolution.

We report on the chemo-dynamical analysis of SPLUS J142445.34-254247.1, an extremely metal-poor halo star enhanced in elements formed by the rapid neutron-capture process. This star was first selected as a metal-poor candidate from its narrow-band S-PLUS photometry and followed up spectroscopically in medium-resolution with Gemini South/GMOS, which confirmed its low-metallicity status. High-resolution spectroscopy was gathered with GHOST at Gemini South, allowing for the determination of chemical abundances for 36 elements, from carbon to thorium. At [Fe/H]=-3.39, SPLUS J1424-2542 is one of the lowest metallicity stars with measured Th and has the highest logeps(Th/Eu) observed to date, making it part of the "actinide-boost" category of r-process enhanced stars. The analysis presented here suggests that the gas cloud from which SPLUS J1424-2542 was formed must have been enriched by at least two progenitor populations. The light-element (Z<=30) abundance pattern is consistent with the yields from a supernova explosion of metal-free stars with 11.3-13.4 Msun, and the heavy-element (Z>=38) abundance pattern can be reproduced by the yields from a neutron star merger (1.66Msun and 1.27Msun) event. A kinematical analysis also reveals that SPLUS J1424-2542 is a low-mass, old halo star with a likely in-situ origin, not associated with any known early merger events in the Milky Way.

In this work, we investigate the discovery potential of low-mass Galactic dark matter (DM) subhaloes for indirect searches of DM. We use data from the Via Lactea II (VL-II) N-body cosmological simulation, which resolves subhaloes down to $\mathcal{O}(10^4)$ solar masses and it is thus ideal for this purpose. First, we characterize the abundance, distribution and structural properties of the VL-II subhalo population in terms of both subhalo masses and maximum circular velocities. Then, we repopulate the original simulation with millions of subhaloes of masses down to about five orders of magnitude below the minimum VL-II subhalo mass (more than one order of magnitude in velocities). We compute subhalo DM annihilation astrophysical"J-factors"and angular sizes for the entire subhalo population, by placing the Earth at a random position but at the right galactocentric distance in the simulation. Thousands of these realizations are generated in order to obtain statistically meaningful results. We find that some nearby low-mass Galactic subhaloes, not massive enough to retain stars or gas, may indeed yield DM annihilation fluxes comparable to those expected from other, more massive and acknowledgeable DM targets like dwarf satellite galaxies. Typical angular sizes are of the order of the degree, thus subhaloes potentially appearing as extended sources in gamma-ray telescopes, depending on instrument angular resolution and sensitivity. Our work shows that low-mass Galactic subhaloes with no visible counterparts are expected to play a relevant role in current and future indirect DM search searches and should indeed be considered as excellent DM targets.

The Gemini High-resolution Optical SpecTrograph (GHOST) is the newest high-resolution spectrograph to be developed for a large-aperture telescope, recently deployed and commissioned at the Gemini-South telescope. In this paper, we present the first science results from the GHOST spectrograph taking during its commissioning runs. We have observed the bright metal-poor benchmark star HD 122563, along with two stars in the ultrafaint dwarf galaxy Reticulum II (Ret ii ), one of which was previously identified as a candidate member, but did not have a previous detailed chemical abundance analysis. We find that this candidate (GDR3 0928) to be a bona fide member of Ret ii , and from a spectral synthesis analysis it is also revealed to be a CEMP- r star, with significant enhancements in several light elements (C, N, O, Na, Mg, and Si), in addition to featuring an r -process enhancement like many other Ret ii stars. The light-element enhancements in this star resemble the abundance patterns seen in the CEMP-no stars of other ultrafaint dwarf galaxies, and are thought to have been produced by an independent source from the r -process. These unusual abundance patterns are thought to be produced by faint supernovae, which may be produced by some of the earliest generations of stars.

ABSTRACT Pristine_183.6849 + 04.8619 (P1836849) is an extremely metal-poor ([Fe/H] = −3.3 ± 0.1) star on a prograde orbit confined to the Galactic disc. Such stars are rare and may have their origins in protogalactic fragments that formed the early Milky Way, in low-mass satellites accreted later, or forming in situ in the Galactic plane. Here, we present a chemo-dynamical analysis of the spectral features between 3700−11 000 Å from a high-resolution spectrum taken during Science Verification of the new Gemini High-resolution Optical SpecTrograph. Spectral features for many chemical elements are analysed (Mg, Al, Si, Ca, Sc, Ti, Cr, Mn, Fe, Ni), and valuable upper limits are determined for others (C, Na, Sr, Ba). This main sequence star exhibits several rare chemical signatures, including (i) extremely low metallicity for a star in the Galactic disc, (ii) very low abundances of the light α-elements (Na, Mg, Si) compared to other metal-poor stars, and (iii) unusually large abundances of Cr and Mn, where [Cr, Mn/Fe]NLTE > +0.5. A comparison to theoretical yields from supernova models suggests that two low-mass Population III objects (one 10 M⊙ supernova and one 17 M⊙ hypernova) can reproduce the abundance pattern well (reduced χ2 < 1). When this star is compared to other extremely metal-poor stars on quasi-circular, prograde planar orbits, differences in both chemistry and kinematics imply there is little evidence for a common origin. The unique chemistry of P1836849 is discussed in terms of the earliest stages in the formation of the Milky Way.

The first stars were born from chemically pristine gas. They were likely massive, and thus they rapidly exploded as supernovae, enriching the surrounding gas with the first heavy elements. In the Local Group, the chemical signatures of the first stellar population were identified among low-mass, long-lived, very metal-poor ([Fe/H]<-2) stars, characterized by high abundances of carbon over iron ([C/Fe]>+0.7): the so-called carbon-enhanced metal-poor stars. Conversely, a similar carbon excess caused by first-star pollution was not found in dense neutral gas traced by absorption systems at different cosmic time. Here we present the detection of 14 very metal-poor, optically thick absorbers at redshift z 3-4. Among these, 3 are carbon-enhanced and reveal an overabundance with respect to Fe of all the analyzed chemical elements (O, Mg, Al, and Si). Their relative abundances show a distribution with respect to [Fe/H] that is in very good agreement with those observed in nearby very metal-poor stars. All the tests we performed support the idea that these C-rich absorbers preserve the chemical yields of the first stars. Our new findings suggest that the first-star signatures can survive in optically thick but relatively diffuse absorbers, which are not sufficiently dense to sustain star formation and hence are not dominated by the chemical products of normal stars.