arXiv subjects

Catarina M. J. Marques

Publications and source records attributed to Catarina M. J. Marques.

5 recordsLinked to original sources

arXiv2026

Estimating the completeness of the QUBRICS Survey with 3501 QSO redshifts from Gaia DR3 spectra

QSOs are essential for investigating the structure and evolution of the Universe. Historically, their identification has been concentrated in the northern hemisphere, primarily due to the sky coverage of major astronomical surveys. The QUBRICS survey, started in 2019 to address this asymmetry, has identified more than 1300 new bright (i<19.5) high-redshift (2.5 2.5 fell within the XGB dataset footprint, of which 152 were unclassified and thus eligible for completeness testing. Similarly, 675 QSOs with z>2.5 were within the PRF dataset footprint, including 69 unclassified objects. The XGB correctly identified as candidates 136 (89%) of the 152 QSOs with z>2.5 present in its dataset as unclassified objects. The PRF correctly identified as candidates 46 (66%) of the 69 QSOs with z>2.5 present in its dataset as unclassified objects. These findings confirm the high efficiency of the QUBRICS selection methods (recall=89%) and provide the completeness estimate for spectroscopically confirmed QSOs (82%), necessary for cosmological studies using QUBRICS data. This work also provides reliable redshifts for 1223 new QSOs (median redshift z=2.1 and magnitude G=17.8), that will help improve the performance of future selections.

astro-ph.CO↗

arXiv2026

The ESPRESSO Redshift Drift Experiment III -- The Third Epoch of QSO J052915.80-435152.0

The Sandage-Loeb test probes cosmic expansion directly by measuring the redshift drift in quasar absorption features in a model-independent way. In this series of papers, we have launched an observational campaign to assess whether current instrumentation is capable of measuring this effect and what systematic effects might interfere with a detection. We report the observations and analysis of the third epoch of ESPRESSO observations of the bright quasar J052915.80-435152.0 (SB2, z=3.962), extending the temporal baseline to $\sim2$ years, and providing the tightest constraints on the redshift drift in the series so far. We acquired 9.5 hours of ESPRESSO observations, complementing the 12 hours presented in the first paper of the series, with one year of separation from the second epoch. The complete dataset was analysed and compared to spline-based Lyman-$α$ forest models calibrated on simulations, to measure the presence of any velocity drift among the spectra. The measurement was carried out with two independent methods. Both approaches give a consistent null result, $\dot{v} = -3.5 \pm 3.6 ~{\rm m s^{-1} yr^{-1}}$ (or $\dot{z} = (-5.3\pm5.6)\times 10^{-8}~{\rm yr^{-1}}$ in redshift space), in agreement with $Λ$CDM expectations, systematic effects remain subdominant at the present level of noise. By extrapolating the results from the observed sightline to the complete QUBRICS Golden Sample, we show that ESPRESSO alone could detect the signal on century timescales, while a joint ESPRESSO+ANDES programme would reach first detection before 2080. A future analysis of the other quasars of the QUBRICS Golden Sample is required to improve this estimate. We show that the program would greatly benefit from a complementary effort with radio facilities targeting low-z HI 21 cm absorption lines. Such synergy could reduce the experiments' timeline by up to $\sim10$ years.

astro-ph.CO↗

arXiv2025

The ESPRESSO Redshift Drift Experiment I -- High-resolution spectra of the Lyman-$α$ forest of QSO J052915.80-435152.0

The measurement of the temporal evolution in the redshift of distant objects, the redshift drift, is a probe of universal expansion and cosmology. We perform the first steps towards a measurement of such effect using the Lyman-$α$ forest in the spectra of bright quasars as a tracer of cosmological expansion. Our goal is to determine to which precision a velocity shift measurement can be carried out with the signal-to-noise (S/N) level currently available and whether this precision aligns with previous theoretical expectations. A precise assessment of the achievable measurement precision is fundamental for estimating the time required to carry out the whole project. We acquire 12 hours of ESPRESSO observations distributed over 0.875 years of the brightest quasar known, J052915.80-435152.0 (z=3.962), to obtain high-resolution spectra of the Lyman-$α$ forest, with median S/N of ~86 per 1 km/s pixel at the continuum. We divide the observations into two epochs and analyse them using both a pixel-by-pixel method and a model-based approach. This comparison allows us to estimate the velocity shift between the epochs, as well as the velocity precision that can be achieved at this S/N. The model-based method is calibrated using high-resolution simulations of the intergalactic medium, and it provides greater accuracy compared to the pixel-by-pixel approach. We measure a velocity drift of the Lyman-$α$ forest consistent with zero: $Δv = -1.25\pm 4.45 {\rm ms^{-1}}$, equivalent to a cosmological drift of $\dot{v}=-1.43\pm 5.09 {\rm ms^{-1}yr^{-1}}$ or $\dot{z}= (-2.19\pm7.77) \times 10^{-8}{\rm yr^{-1}}$. The measurement uncertainties are on par with the expected precision. We estimate that reaching a 99% detection of the cosmic drift requires a monitoring campaign of 5400 hours of integration time over 54 years with an ELT and an ANDES-like high-resolution spectrograph.

astro-ph.CO↗

arXiv2023

Spectroscopy of QUBRICS quasar candidates: 1672 new redshifts and a Golden Sample for the Sandage Test of the Redshift Drift

The QUBRICS (QUasars as BRIght beacons for Cosmology in the Southern hemisphere) survey aims at constructing a sample of the brightest quasars with z>~2.5, observable with facilities in the Southern Hemisphere. QUBRICS makes use of the available optical and IR wide-field surveys in the South and of Machine Learning techniques to produce thousands of bright quasar candidates of which only a few hundred have been confirmed with follow-up spectroscopy. Taking advantage of the recent Gaia Data Release 3, which contains 220 million low-resolution spectra, and of a newly developed spectral energy distribution fitting technique, designed to combine the photometric information with the Gaia spectroscopy, it has been possible to measure 1672 new secure redshifts of QUBRICS candidates, with a typical uncertainty $σ_z = 0.02$. This significant progress of QUBRICS brings it closer to (one of) its primary goals: providing a sample of bright quasars at redshift 2.5 < z < 5 to perform the Sandage test of the cosmological redshift drift. A Golden Sample of seven quasars is presented that makes it possible to carry out this experiment in about 1500 hours of observation in 25 years, using the ANDES spectrograph at the 39m ELT, a significant improvement with respect to previous estimates.

astro-ph.CO↗

arXiv2022

Fundamental Physics with ESPRESSO, Constraining a simple parametrisation for varying $α$

The spectrograph ESPRESSO recently obtained a limit on the variation of the fine-structure constant, $α$, through measurements along the line of sight of a bright quasar with a precision of $1.36$ ppm at $1σ$ level. This imposes new constraints on cosmological models with a varying $α$. We assume such a model where the electromagnetic sector is coupled to a scalar field dark energy responsible for the current acceleration of the Universe. We parametrise the variation of $α$ with two extra parameters, one defining the cosmological evolution of the quintessence component and the other fixing the coupling with the electromagnetic field. The objective of this work is to constrain these parameters with both astrophysical and local probes. We also carried out a comparative analysis of how each data probe may constrain our parametrisation. We performed a Bayesian analysis by comparing the predictions of the model with observations. The astrophysical datasets are composed of quasar spectra measurements, including the latest ESPRESSO data point, as well as Planck observations of the cosmic microwave background. We combined these with local results from atomic clocks and the MICROSCOPE experiment. The constraints placed on the quintessence parameter are consistent with a null variation of the field, and are therefore compatible with a $Λ$CDM cosmology. The constraints on the coupling to the electromagnetic sector are dominated by the Eötvös parameter local bound. More precise measurements with ESPRESSO will be extremely important to study the cosmological evolution of $α$ as it probes an interval of redshift not accessible to other types of observations. However, for this particular model, current available data favour a null variation of $α$ resulting mostly from the strong MICROSCOPE limits.

astro-ph.CO↗