arXiv subjects

Esperanza Carrasco

Publications and source records attributed to Esperanza Carrasco.

14 recordsLinked to original sources

arXiv2026

The WEAVE acquisition and guiding software: pattern recognition-based acquisition and multi-fibre guiding

We present the architecture, implementation, and on-sky validation of the fully automated acquisition and guiding system (AG) developed for the WEAVE instrument on the William Herschel Telescope. The AG operates in two distinct modes, corresponding to the observing modes of WEAVE. For the large integral field unit (LIFU), an off-axis imaging guider is used, for which we have devised an automatic acquisition method based on pattern recognition of stellar asterisms matched against Gaia predictions. For the multi-object spectrograph (MOS) and the mini-integral field units (mIFU), a multi-fibre guider uses up to eight coherent image guide fibre bundles to derive and apply continuous corrections in azimuth, altitude, and rotation. The system performs complete astrometric calculations, including atmospheric differential refraction and instrument flexure, for each guide frame, enabling accurate target placement and stable closed-loop guiding in all configurations. To support development, commissioning, and operational validation, we have also built a high-fidelity simulation mode that reproduces the behaviour of the telescope control system and of the AG cameras, and we release the standalone camera simulator as open-source software. Using two years of routine WEAVE operations spanning commissioning and early survey phases, we present a statistically robust characterization of AG performance, demonstrating that both modes meet design requirements and are ready for sustained survey operations.

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arXiv2025

The WEAVE-TwiLight-Survey: Expanding WEAVE's Reach to Bright and Low-Surface-Density Targets with a Novel Observing Mode

Current-day multi-object spectroscopic surveys are often limited in their ability to observe bright stars due to their low surface densities, resulting in increased observational overheads and reduced efficiency. Addressing this, we have developed a novel observing mode for WEAVE (William Herschel Telescope Enhanced Area Velocity Explorer) that enables efficient observations of low-surface-density target fields without incurring additional overheads from calibration exposures. As a pilot for the new mode, we introduce the WEAVE-TwiLight-Survey (WTLS), focusing on bright exoplanet-host stars and their immediate surroundings on the sky. High observational efficiency is achieved by superimposing multiple low-target-density fields and allocating the optical fibres in this configuration. We use a heuristic method to define fields relative to a central guide star, which serves as a reference for their superposition. Suitable guide fibres for each merged configuration are selected using a custom algorithm. Test observations have been carried out, demonstrating the feasibility of the new observing mode. We show that merged field configurations can be observed with WEAVE using the proposed method. The approach minimizes calibration times and opens twilight hours to WEAVE's operational schedule. WTLS is built upon the new observing mode and sourced from the ESA PLATO long-duration-phase fields. This survey will result in a homogeneous catalogue of approximately 6300 bright stars, including 62 known planet hosts, laying the groundwork for future elemental abundance studies tracing chemical patterns of planetary formation. This new observing mode (WEAVE-Tumble-Less) expands WEAVE's capabilities to rarely used on-sky time and low-density field configurations without sacrificing efficiency.

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arXiv2023

Once in a blue stream: Detection of recent star formation in the NGC 7241 stellar stream with MEGARA

In this work we study the striking case of a narrow blue stream around the NGC 7241 galaxy and its foreground dwarf companion. We want to figure out if the stream was generated by tidal interaction with NGC 7241 or it first interacted with the foreground dwarf companion and later both fell together towards NGC 7241. We use four sets of observations, including a follow-up spectroscopic study with the MEGARA instrument at the 10.4-m Gran Telescopio Canarias. Our data suggest that the compact object we detected in the stream is a foreground Milky Way halo star. Near this compact object we detect emission lines overlapping a bluer and fainter blob of the stream that is clearly visible in both ultra-violet and optical deep images. From its heliocentric systemic radial velocity (Vsyst= 1548.58+/-1.80 km s^-1) and new UV and optical broad-band photometry, we conclude that this over-density could be the actual core of the stream, with an absolute magnitude of M_g ~ -10 and a (g-r) = 0.08 +/- 0.11, consistent with a remnant of a low-mass dwarf satellite undergoing a current episode of star formation. From the width of the stream and assuming a circular orbit, we calculate that the progenitor mass can be the typical of a dwarf galaxy, but it could also be substantially lower if the stream is on a very radial orbit or it was created by tidal interaction with the companion dwarf instead of with NGC 7241. Finally, we find that blue stellar streams containing star formation regions are commonly predicted by high-resolution cosmological simulations of galaxies lighter than the Milky Way. This scenario is consistent with the processes explaining the bursty star formation history of some dwarf satellites, which are followed by a gas depletion and a fast quenching once they enter within the virial radius of their host galaxies for the first time.

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arXiv2023

The wide-field, multiplexed, spectroscopic facility WEAVE: Survey design, overview, and simulated implementation

WEAVE, the new wide-field, massively multiplexed spectroscopic survey facility for the William Herschel Telescope, will see first light in late 2022. WEAVE comprises a new 2-degree field-of-view prime-focus corrector system, a nearly 1000-multiplex fibre positioner, 20 individually deployable 'mini' integral field units (IFUs), and a single large IFU. These fibre systems feed a dual-beam spectrograph covering the wavelength range 366$-$959\,nm at $R\sim5000$, or two shorter ranges at $R\sim20\,000$. After summarising the design and implementation of WEAVE and its data systems, we present the organisation, science drivers and design of a five- to seven-year programme of eight individual surveys to: (i) study our Galaxy's origins by completing Gaia's phase-space information, providing metallicities to its limiting magnitude for $\sim$3 million stars and detailed abundances for $\sim1.5$ million brighter field and open-cluster stars; (ii) survey $\sim0.4$ million Galactic-plane OBA stars, young stellar objects and nearby gas to understand the evolution of young stars and their environments; (iii) perform an extensive spectral survey of white dwarfs; (iv) survey $\sim400$ neutral-hydrogen-selected galaxies with the IFUs; (v) study properties and kinematics of stellar populations and ionised gas in $z<0.5$ cluster galaxies; (vi) survey stellar populations and kinematics in $\sim25\,000$ field galaxies at $0.3\lesssim z \lesssim 0.7$; (vii) study the cosmic evolution of accretion and star formation using $>1$ million spectra of LOFAR-selected radio sources; (viii) trace structures using intergalactic/circumgalactic gas at $z>2$. Finally, we describe the WEAVE Operational Rehearsals using the WEAVE Simulator.

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arXiv2022

Optimisation of the WEAVE target assignment algorithm

WEAVE is the new wide-field spectroscopic facility for the prime focus of the William Herschel Telescope in La Palma, Spain. Its fibre positioner is essential for the accurate placement of the spectrograph's ~960-fibre multiplex. To maximise the assignment of its optical fibres, WEAVE uses a simulated annealing algorithm called Configure, which allocates the fibres to targets in the field of view. We have conducted an analysis of the algorithm's behaviour using a subset of mid-tier WEAVE-LOFAR fields, and adjusted the priority assignment algorithm to optimise the total fibres assigned per field, and the assignment of fibres to the higher priority science targets. The output distributions have been examined, to investigate the implications for the WEAVE science teams.

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arXiv2020

Final assembly, metrology, and testing of the WEAVE fibre positioner

WEAVE is the new wide-field spectroscopy facility for the prime focus of the William Herschel Telescope at La Palma, Spain. Its fibre positioner is essential for the accurate placement of the spectrograph's 960 fibre multiplex. We provide an overview of the final assembly and metrology of the fibre positioner, and results of lab commissioning of its robot gantries. A completely new z-gantry for each positioner robot was acquired, with measurements showing a marked improvement in positioning repeatability. We also present the first results of the configuration software testing, and discuss the metrology procedures that must be repeated after the positioner's arrival at the observatory.

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arXiv2020

High Resolution Spectral Line Indices Useful for the Analysis of Stellar Populations

The well-known age-metallicity-attenuation degeneracy does not permit unique and good estimates of basic parameters of stars and stellar populations. The effects of dust can be avoided using spectral line indices, but current methods have not been able to break the age-metallicity degeneracy. Here we show that using at least two new spectral line indices defined and measured on high-resolution (R= 6000) spectra of a signal-to-noise ratio (S/N) > 10 one gets unambiguous estimates of the age and metallicity of intermediate to old stellar populations. Spectroscopic data retrieved with new astronomical facilities, e.g., X-shooter, MEGARA, and MOSAIC, can be employed to infer the physical parameters of the emitting source by means of spectral line index and index--index diagram analysis.

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arXiv2018

High-resolution MEGARA IFU spectroscopy and structural analysis of a fast-rotating, disky bulge in NGC 7025

Disky bulges in spiral galaxies are commonly thought to form out of disk materials (mainly) via bar driven secular processes, they are structurally and dynamically distinct from `classical bulges' built in violent merger events. We use high-resolution GTC/MEGARA integral-field unit spectroscopic observations of the Sa galaxy NGC 7025, obtained during the MEGARA commissioning run, together with detailed 1D and 2D decompositions of this galaxy's SDSS $i$-band data to investigate the formation of its disky (bulge) component which makes up $\sim 30\%$ of the total galaxy light. With a Sérsic index $n \sim 1.80 \pm 0.24$, half-light radius $R_{\rm e} \sim 1.70 \pm 0.43$ kpc and stellar mass $M_{*} \sim (4.34 \pm 1.70) \times10^{10} M_{\odot}$, this bulge dominates the galaxy light distribution in the inner $R \sim 15"$ ($\sim 4.7$ kpc). Measuring the spins ($λ$) and ellipticities ($ε$) enclosed within nine different circular apertures with radii $R \le R_{\rm e}$, we show that the bulge, which exhibits a spin track of an outwardly rising $λ$ and $ε$, is a fast rotator for all the apertures considered. Our findings suggest that this inner disky component is a pseudo-bulge, consistent with the stellar and dust spiral patterns seen in the galaxy down to the innermost regions but in contrast to the classical bulge interpretation favored in the past. We propose that a secular process involving the tightly wound stellar spiral arms of NGC 7025 may drive gas and stars out of the disk into the inner regions of the galaxy, building up the massive pseudo-bulge.

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arXiv2004

High altitude wind velocity at Sierra Negra and San Pedro Mártir

It has been proposed that the global circulation of the atmosphere winds at 200 mb can be used as a criteria to establish the suitability of a site for the development of adaptive optics techniques such as slow wavefront corrugation correction. By using the NOAA NCEP/NCAR Reanalysis data base we analyze the monthly average wind velocity at 200 mb for a 16 year period, for two sites in Mexico: Sierra Negra and San Pedro Mártir. We compare the results with those obtained for Mauna Kea, Paranal and La Silla, with Maidanak in Uzbekistan, and with Gamsberg in Namibia. We show that for all the sites under study there is a yearly wind speed modulation and we model that modulation. Our results show that Sierra Negra and San Pedro Mártir are comparable with the best observatory sites as Mauna Kea and are amongst the most advantageous sites to apply adaptive optics techniques.

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arXiv2003

High altitude wind velocity at San Pedro Martir and Mauna Kea

We analyze the monthly average wind velocity at about 12 km above sea level, between 1980 to 1995, for San Pedro Martir, Mauna Kea, another existing observatorie and some sites of interest. We compare the results obtained from two different data sets, the GGUAS and NCEP. Our results show that San Pedro Martir and Mauna Kea are comparable and are amongst the most suitable sites to apply slow wavefront corrugation correction techniques

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arXiv2003

Optical Seeing at Sierra Negra

Optical seeing measurements carried out at Sierra Negra, the site of the Large Millimeter Telescope, are reported. The site, one of the highest peaks of Central Mexico, offers good coverage of Northern and Southern hemispheres and we have undertaken several campaigns to investigate the astronomical potential of the site in the optical. Here we report on our campaign aimed at establishing the seeing quality of the site. We present data of the first three campaigns of optical seeing monitoring covering from February 2000 to May 2002, carried out with a Differential Image Motion Monitor. The results clearly indicate a sub-arcsec seeing, better statistics during the dry season and no dependence with the time of night. We find no dependence of our results with the integration time used.

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arXiv2000

The IRAS view of the Local Universe

We summarise results for the predicted density and peculiar velocity fields from the PSCz survey. We have used a generalisation of the Path Interchange Zeldovich Approximation to determine the velocity field; the most remarkable feature being a coherent large-scale flow along the baseline connecting the Local Supercluster, Centaurus and the Shapley Concentration. Comparison of the predicted and observed bulk flows gives a value of beta = 0.50+-0.1. We re-examine the PSCz dipole, with improved redshift completeness at low-latitudes and using PIZA to estimate real-space distances. We find the dipole to be stable between 80 and 180 hMpc, although there appears to be a significant contribution to the dipole around 200 hMpc. The overall misalignment with the CMB dipole remains at 20degrees. The implied value of beta is in the range 0.40-0.55 with statistical error +-0.1. We also present the density field and a preliminary dipole analysis from the almost completed Behind The Plane survey, which extends the PSCz to cover 93% of the sky including the proposed core of the Great Attractor. We find a density peak at (325,-5,3500km/s), about half as massive as Centaurus or Pavo-Indus, and forming part of a continuous filament linking them across the Plane. We also find evidence for a much larger `Greater Attractor' directly behind the GA, at a distance of 125 hMpc, and more massive than the Shapley concentration. At large distances the dipole direction is in much improved agreement with the CMB: at 250-300hMpc, the misalignment is only 5-10 degrees, though this depends on the incompleteness corrections made. The dipole amplitude implies a value for the parameter beta of 0.44+-0.1.

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arXiv2000

The Behind The Plane Survey - source selection, identifications and completeness

We present details of the Behind The Plane survey of IRAS galaxies, which extends the PSCz survey to cover the 93% of the sky with complete and reliable IRAS data from the Point Source Catalog. At low latitudes, our catalogue is not complete to 0.6Jy, but the incompleteness is physically understood and can be corrected for. IRAS galaxies at low latitudes are heavily or completely obscured optically, and are heavily outnumbered by Galactic sources with similar IRAS properties. We have used radio, optical, mm, near and far-infrared data to identify the galaxies, and the 2D catalogue is now complete. We have used optical and HI spectroscopy to obtain redshifts for the galaxies; the southern spectroscopy is completed and the north nearly so.

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arXiv1999

The Behind The Plane Survey

We have extended the PSCz to cover 93% of the sky, the practical limit for any catalogue based on the Point Source Catalog. The galaxy identifications are complete, and the core of the Great Attractor is quantitatively mapped for the first time. We discuss the likely effect of the increased sky coverage on the IRAS dipole.

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