M. Bellazzini; D. Massari; De Angeli F.; A. Mucciarelli; A Bragaglia.; M. Riello; P. Montegriffo
arXiv (Cornell University) · DOI ↗
We use the calibrations by Calamida et al. and by Hilker et al., and the standardised synthetic photometry in the v, b, and y Stromgren passbands from Gaia DR3 BP/RP spectra, to obtain photometric metallicities for a selected sample of 694233 old Galactic giant stars having |b|>20.0 and parallax uncertainties lower than 10%. The zero point of both sets of photometric metallicities has been shifted to to ensure optimal match with the spectroscopic [Fe/H] values for 44785 stars in common with APOGEE DR17, focusing on the metallicity range where they provide the highest accuracy. The metallicities derived in this way from the Calamida et al. calibration display a typical accuracy of ~0.1 dex and 1 sigma precision ~0.2 dex in the range -2.2 <=[Fe/H]<= -0.4, while they show a systematic trend with [Fe/H] at higher metallicity, beyond the applicability range of the relation. Those derived from the Hilker et al. calibration display, in general, worse precision, and lower accuracy in the metal-poor regime, but have a median accuracy < 0.05 dex for [Fe/H]>= -0.8. These results are confirmed and, consequently, the metallicities validated, by comparison with large sets of spectroscopic metallicities from various surveys. The newly obtained metallicities are used to derive metallicity distributions for several previously identified sub-structures in the Galactic halo with an unprecedented number of stars. The catalogue including both sets of metallicities and the associated uncertainties is made publicly available.
Sumedha Biswas; Z. Kostrzewa-Rutkowska; P. G. Jonker; P. M. Vreeswijk; D. Eappachen; P. Groot; S. T. Hodgkin; Abdullah Yoldaş; G. Rixon; D. L. Harrison; M. van Leeuwen; D. W. Evans
Monthly Notices of the Royal Astronomical Society · DOI ↗
ABSTRACT The discovery of gravitational wave (GW) events and the detection of electromagnetic counterparts from GW170817 has started the era of multimessenger GW astronomy. The field has been developing rapidly, and in this paper, we discuss the preparation for detecting these events with ESA’s Gaia satellite, during the 4th observing run of the LIGO–Virgo–KAGRA (LVK) collaboration that has started on 2023 May 24. Gaia is contributing to the search for GW counterparts by a new transient detection pipeline called GaiaX. In GaiaX, a new source appearing in the field of view of only one of the two telescopes on-board Gaia is sufficient to send out an alert on the possible detection of a new transient. Ahead of O4, an experiment was conducted over a period of about two months. During the two weeks around New Moon in this period of time, the MeerLICHT (ML) telescope located in South Africa tried (weather permitting) to observe the same region of the sky as Gaia within 10 min. Any GaiaX detected transient was published publicly. ML and Gaia have similar limiting magnitudes for typical seeing conditions at ML. At the end of the experiment, we had 11 861 GaiaX candidate transients and 15 806 ML candidate transients, which we further analysed and the results of which are presented in this paper. Finally, we discuss the possibility and capabilities of Gaia contributing to the search for electromagnetic counterparts of gravitational wave events during O4 through the GaiaX detection and alert procedure.
Laura K. Rogers; Amy Bonsor; Siyi Xu; P. Dufour; B. Klein; Andrew M. Buchan; S. T. Hodgkin; François Hardy; M. Kissler‐Patig; Carl Melis; Alycia J. Weinberger; B. Zuckerman
Monthly Notices of the Royal Astronomical Society · DOI ↗
ABSTRACT Observations of planetary material polluting the atmospheres of white dwarfs are an important probe of the bulk composition of exoplanetary material. Medium- and high-resolution optical and ultraviolet spectroscopy of seven white dwarfs with known circumstellar dust and gas emission are presented. Detections or meaningful upper limits for photospheric absorption lines are measured for: C, O, Na, S, P, Mg, Al, Si, Ca, Ti, Cr, Fe, and Ni. For 16 white dwarfs with known observable gaseous emission discs (and measured photospheric abundances), there is no evidence that their accretion rates differ, on average, from those without detectable gaseous emission. This suggests that, typically, accretion is not enhanced by gas drag. At the effective temperature range of the white dwarfs in this sample (16 000–25 000 K) the abundance ratios of elements are more consistent than absolute abundances when comparing abundances derived from spectroscopic white dwarf parameters versus photometric white dwarf parameters. Crucially, this highlights that the uncertainties on white dwarf parameters do not prevent white dwarfs from being utilized to study planetary composition. The abundances of oxygen and silicon for the three hydrogen-dominated white dwarfs in the sample with both optical and ultraviolet spectra differ by 0.62 dex depending on if they are derived from the optical or ultraviolet spectra. This optical/ultraviolet discrepancy may be related to differences in the atmospheric depth of line formation; further investigations into the white dwarf atmospheric modelling are needed to understand this discrepancy.
Anke Arentsen; David S. Aguado; Federico Sestito; J. I. Gónzalez Hernández; Nicolas F. Martin; Else Starkenburg; P. Jablonka; Zhen Yuan
Monthly Notices of the Royal Astronomical Society · DOI ↗
ABSTRACT Ultra-metal-poor stars ($\rm {[Fe/H]} \lt -4.0$) are very rare, and finding them is a challenging task. Both narrow-band photometry and low-resolution spectroscopy have been useful tools for identifying candidates, and in this work, we combine both approaches. We cross-matched metallicity-sensitive photometry from the Pristine survey with the low-resolution spectroscopic Large Sky Area Multi-Object Fibre Spectroscopic Telescope (LAMOST) data base, and re-analysed all LAMOST spectra with $\rm {[Fe/H]} _{\rm Pristine} \lt -2.5$. We find that ∼1/3rd of this sample (selected without $\rm {[Fe/H]} _{\rm Pristine}$ quality cuts) also have spectroscopic $\rm {[Fe/H]} \lt -2.5$. From this sample, containing many low signal-to-noise ratio (S/N) spectra, we selected 11 stars potentially having $\rm {[Fe/H]} \lt -4.0$ or $\rm {[Fe/H]} \lt -3.0$ with very high carbon abundances, and we performed higher S/N medium-resolution spectroscopic follow-up with the Optical System for Imaging and low Resolution Integrated Spectroscopy (OSIRIS) on the 10.4-m Gran Telescopio Canarias (GTC). We confirm their extremely low metallicities, with a mean of $\rm {[Fe/H]} = -3.4$, and the most metal-poor star having $\rm {[Fe/H]} = -3.8$. Three of these are clearly carbon-enhanced metal-poor (CEMP) stars with $+1.65 \lt \rm {[C/Fe]} \lt +2.45$. The two most carbon-rich stars are either among the most metal-poor CEMP-s stars or the most carbon-rich CEMP-no stars known, the third is likely a CEMP-no star. We derived orbital properties for the OSIRIS sample and find that only one of our targets can be confidently associated with known substructures/accretion events, and that three out of four inner halo stars have prograde orbits. Large spectroscopic surveys may contain many hidden extremely and ultra-metal-poor stars, and adding additional information from e.g. photometry as in this work can uncover them more efficiently and confidently.
L. Mashonkina; Anke Arentsen; David S. Aguado; A Smogorzhevskii; Matías Rolf Hampel; Amanda I. Karakas; Federico Sestito; Nicolas F. Martin; Kim A. Venn; J. I. Gónzalez Hernández
Monthly Notices of the Royal Astronomical Society · DOI ↗
ABSTRACT Well-studied very metal-poor (VMP, [Fe/H] <−2) stars in the inner Galaxy are few in number, and they are of special interest because they are expected to be among the oldest stars in the Milky Way. We present high-resolution spectroscopic follow-up of the carbon-enhanced metal-poor (CEMP) star Pristine_184237.56-260624.5 (hereafter Pr184237) identified in the Pristine Inner Galaxy Survey. This star has an apocentre of ∼2.6 kpc. Its atmospheric parameters (Teff = 5100 K, log g = 2.0, and [Fe/H] = −2.60) were derived based on the non-local thermodynamic equilibrium (NLTE) line formation. We determined abundances for 32 elements, including 15 heavy elements beyond the iron group. The NLTE abundances were calculated for 13 elements from Na to Pb. Pr184237 is strongly enhanced in C, N, and O, and both s- and r-process elements from Ba to Pb; it reveals a low carbon isotope ratio of 12C/13C = 7. The element abundance pattern in the Na–Zn range is typical of halo stars. With [Ba/Eu] = 0.32, Pr184237 is the first star of the CEMP-r/s subclass identified in the inner Galaxy. Variations in radial velocity suggest binarity. We tested whether a pollution by the s- or i-process material produced in the more massive and evolved companion can form the observed abundance pattern and find that an i-process in the asymptotic giant branch star with a progenitor mass of 1.0–2.0 $\, {\rm M}_{\odot }$ can be the solution.
Sakurako Okamoto; N. Arimoto; A. M. N. Ferguson; M. J. Irwin; Rokas Žemaitis
The Astrophysical Journal · DOI ↗
Abstract We present a study of the structural properties and metallicity distribution of the nearby peculiar galaxy NGC 3077. Using data from our survey of the M81 Group with the Hyper Suprime-Cam on board the Subaru Telescope, we construct deep color–magnitude diagrams that are used to probe the old red giant branch (RGB) population of NGC 3077. We map these stars out to and beyond the nominal tidal radius, which allows us to derive the structural properties and stellar content of the peripheral regions. We show that NGC 3077 has an extended stellar halo and pronounced “S-shaped” tidal tails that diverge from the radial profile of the inner region. The average metallicity of the old population in NGC 3077 is estimated from individual RGBs to be [M/H] = −0.98 ± 0.26, which decreases with the distance from the galaxy center as [M/H] = −0.17 dex <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML&quot; overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mi>R</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>h</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> . The metallicity of the S-shaped structure is similar to that of the regions lying at r ∼ 4 × R h ( ∼ 30 kpc), indicating that the stellar constituents of the tidal tails have come from the outer envelope of NGC 3077. These results suggest that this peculiar galaxy was probably a rather normal dwarf elliptical galaxy before the tidal interaction with M81 and M82. We also examine the evidence in our data set for the six recently reported ultrafaint dwarf candidates around NGC 3077. We recover a spatial overdensity of sources coinciding with only one of these.
Alice M Eltvedt; T. Shanks; N. Metcalfe; Behzad Ansarinejad; L. Felipe Barrientos; R. Sharp; U Malik; D. N. A. Murphy; M. J. Irwin; Michael Wilson; D. M. Alexander; András Kovács; J. García-Bellido; S. P. Ahlen; D. Brooks; Axel de la Macorra; Andreu Font-Ribera; Satya Gontcho A Gontcho; K. Honscheid; Aaron Meisner; R. Miquel; Jundan Nie; G. Tarlé; M. Vargas-Magaña; Zhimin Zhou
Monthly Notices of the Royal Astronomical Society · DOI ↗
ABSTRACT We present the VST ATLAS Quasar Survey, consisting of ∼1229 000 quasar (QSO) candidates with 16 &amp;lt; g &amp;lt; 22.5 over ∼4700 deg2. The catalogue is based on VST ATLAS+NEOWISE imaging surveys and aims to reach a QSO sky density of 130 deg−2 for $z$ &amp;lt; 2.2 and ∼30 deg−2 for $z$ &amp;gt; 2.2. To guide our selection, we use X-ray/UV/optical/MIR data in the extended William Herschel Deep Field (WHDF) where we find a g &amp;lt; 22.5 broad-line QSO density of 269 ± 67 deg−2, roughly consistent with the expected ∼196 deg−2. We find that ∼25 per cent of our QSOs are morphologically classed as optically extended. Overall, we find that in these deep data, MIR, UV, and X-ray selections are ∼70–90 per cent complete while X-ray suffers less contamination than MIR and UV. MIR is however more sensitive than X-ray or UV to $z$ &amp;gt; 2.2 QSOs at g &amp;lt; 22.5 and the $S_X(0.5-10\, {\rm keV})\gt 1\times 10^{-14}$ ergs cm−2 s−1 limit of eROSITA. We adjust the selection criteria from our previous 2QDES pilot survey and prioritize VST ATLAS candidates that show both UV and MIR excess, also selecting candidates initially classified as extended. We test our selections using data from DESI (which will be released in DR1) and 2dF to estimate the efficiency and completeness, and we use ANNz2 to determine photometric redshifts. Applying over the ∼4700 deg2 ATLAS area gives us $\sim 917\,000\, z\lt 2.2$ QSO candidates of which 472 000 are likely to be $z$ &amp;lt; 2.2 QSOs, implying a sky density of ∼100 deg−2, which our WHDF analysis suggests will rise to at least 130 deg−2 when eROSITA X-ray candidates are included. At $z$ &amp;gt; 2.2, we find ∼310() 000 candidates, of which 169 000 are likely to be QSOs for a sky density of ∼36 deg−2.
Duncan A. Forbes; Jonah S. Gannon; E. Iodice; M. Hilker; Goran Doll; Chiara Buttitta; Antonio La Marca; M. Arnaboldi; Michele Cantiello; G. D’Ago; J. Falcón‐Barroso; L. Greggio; Marco Gullieuszik; Johanna Hartke; Steffen Mieske; Marco Mirabile; R. Rampazzo; M. Rejkuba; Marilena Spavone; Chiara Spiniello; Giulio Capasso
Monthly Notices of the Royal Astronomical Society Letters · DOI ↗
ABSTRACT Although ultra diffuse galaxies (UDGs) are found in large numbers in clusters of galaxies, the role of the cluster environment in shaping their low surface brightness and large sizes is still uncertain. Here, we examine a sample of UDGs in the Hydra I cluster (D = 51 Mpc) with new radial velocities obtained as part of the LEWIS (Looking into the faintest with MUSE) project using VLT/MUSE data. Using a phase-space, or infall diagnostic, diagram we compare the UDGs to other known galaxies in the Hydra I cluster and to UDGs in other clusters. The UDGs, along with the bulk of regular Hydra I galaxies, have low relative velocities and are located near the cluster core, and thus consistent with very early infall into the cluster. Combining with literature data, we do not find the expected trend of GC-rich UDGs associated with earlier infall times. This result suggests that quenching mechanisms other than cluster infall should be further considered, e.g. quenching by strong feedback or in cosmic sheets and filaments. Tidal stripping of GCs in the cluster environment also warrants further modelling.
A. Vallenari; A. G. A. Brown; T. Prusti; J. H. J. de Bruijne; F. Arenou; C. Babusiaux; M. Biermann; O. L. Creevey; C. Ducourant; D. W. Evans; et al.
Astronomy and Astrophysics · DOI ↗
Context. We present the third data release of the European Space Agency’s Gaia mission, Gaia DR3. This release includes a large variety of new data products, notably a much expanded radial velocity survey and a very extensive astrophysical characterisation of Gaia sources. Aims. We outline the content and the properties of Gaia DR3, providing an overview of the main improvements in the data processing in comparison with previous data releases (where applicable) and a brief discussion of the limitations of the data in this release. Methods. The Gaia DR3 catalogue is the outcome of the processing of raw data collected with the Gaia instruments during the first 34 months of the mission by the Gaia Data Processing and Analysis Consortium. Results. The Gaia DR3 catalogue contains the same source list, celestial positions, proper motions, parallaxes, and broad band photometry in the G , G BP , and G RP pass-bands already present in the Early Third Data Release, Gaia EDR3. Gaia DR3 introduces an impressive wealth of new data products. More than 33 million objects in the ranges G RVS &lt; 14 and 3100 &lt; T eff &lt; 14 500, have new determinations of their mean radial velocities based on data collected by Gaia . We provide G RVS magnitudes for most sources with radial velocities, and a line broadening parameter is listed for a subset of these. Mean Gaia spectra are made available to the community. The Gaia DR3 catalogue includes about 1 million mean spectra from the radial velocity spectrometer, and about 220 million low-resolution blue and red prism photometer BP/RP mean spectra. The results of the analysis of epoch photometry are provided for some 10 million sources across 24 variability types. Gaia DR3 includes astrophysical parameters and source class probabilities for about 470 million and 1500 million sources, respectively, including stars, galaxies, and quasars. Orbital elements and trend parameters are provided for some 800 000 astrometric, spectroscopic and eclipsing binaries. More than 150 000 Solar System objects, including new discoveries, with preliminary orbital solutions and individual epoch observations are part of this release. Reflectance spectra derived from the epoch BP/RP spectral data are published for about 60 000 asteroids. Finally, an additional data set is provided, namely the Gaia Andromeda Photometric Survey, consisting of the photometric time series for all sources located in a 5.5 degree radius field centred on the Andromeda galaxy. Conclusions. This data release represents a major advance with respect to Gaia DR2 and Gaia EDR3 because of the unprecedented quantity, quality, and variety of source astrophysical data. To date this is the largest collection of all-sky spectrophotometry, radial velocities, variables, and astrophysical parameters derived from both low- and high-resolution spectra and includes a spectrophotometric and dynamical survey of SSOs of the highest accuracy. The non-single star content surpasses the existing data by orders of magnitude. The quasar host and galaxy light profile collection is the first such survey that is all sky and space based. The astrophysical information provided in Gaia DR3 will unleash the full potential of Gaia ’s exquisite astrometric, photometric, and radial velocity surveys.
R. Andrae; M. Fouesneau; R. Sordo; C. A. L. Bailer‐Jones; T. E. Dharmawardena; J. Rybizki; F. De Angeli; H. E. P. Lindstrøm; D. J. Marshall; R. Drimmel; et al.
Astronomy and Astrophysics · DOI ↗
Context. The astrophysical characterisation of sources is among the major new data products in the third Gaia Data Release (DR3). In particular, there are stellar parameters for 471 million sources estimated from low-resolution BP/RP spectra. Aims. We present the General Stellar Parameterizer from Photometry (GSP-Phot), which is part of the astrophysical parameters inference system (Apsis). GSP-Phot is designed to produce a homogeneous catalogue of parameters for hundreds of millions of single non-variable stars based on their astrometry, photometry, and low-resolution BP/RP spectra. These parameters are effective temperature, surface gravity, metallicity, absolute M G magnitude, radius, distance, and extinction for each star. Methods. GSP-Phot uses a Bayesian forward-modelling approach to simultaneously fit the BP/RP spectrum, parallax, and apparent G magnitude. A major design feature of GSP-Phot is the use of the apparent flux levels of BP/RP spectra to derive, in combination with isochrone models, tight observational constraints on radii and distances. We carefully validate the uncertainty estimates by exploiting repeat Gaia observations of the same source. Results. The data release includes GSP-Phot results for 471 million sources with G &lt; 19. Typical differences to literature values are 110 K for T eff and 0.2–0.25 for log g , but these depend strongly on data quality. In particular, GSP-Phot results are significantly better for stars with good parallax measurements ( ϖ / σ ϖ &gt; 20), mostly within 2 kpc. Metallicity estimates exhibit substantial biases compared to literature values and are only useful at a qualitative level. However, we provide an empirical calibration of our metallicity estimates that largely removes these biases. Extinctions A 0 and A BP show typical differences from reference values of 0.07–0.09 mag. MCMC samples of the parameters are also available for 95% of the sources. Conclusions. GSP-Phot provides a homogeneous catalogue of stellar parameters, distances, and extinctions that can be used for various purposes, such as sample selections (OB stars, red giants, solar analogues etc.). In the context of asteroseismology or ground-based interferometry, where targets are usually bright and have good parallax measurements, GSP-Phot results should be particularly useful for combined analysis or target selection.
D. W. Evans; L. Eyer; G. Busso; M. Riello; F. De Angeli; P. W. Burgess; M. Audard; G. Clementini; A. Garofalo; B. Holl; G. Jévardat de Fombelle; A. C. Lanzafame; I. Lecœur-Taı̈bi; N. Mowlavï; K. Nienartowicz; L. Palaversa; L. Rimoldini
Astronomy and Astrophysics · DOI ↗
Context. As part of Gaia Data Release 3 ( Gaia DR3), epoch photometry has been released for 1.2 million sources centred on M 31. This is a taster for Gaia Data Release 4 where all the epoch photometry will be released. Aims. In this paper, the content of the Gaia Andromeda Photometric Survey (GAPS) is described, including statistics to assess the quality of the data. Known issues with the photometry are also outlined. Methods. Methods are given to improve interpretation of the photometry, in particular, a method for error renormalisation. Also, use of correlations between the three photometric passbands allows clearer identification of variables, and is not affected by false detections caused by systematic effects. Results. GAPS presents a unique opportunity to look at Gaia epoch photometry that has not been preselected based on variability. This allows investigations to be carried out that can be applied to the rest of the sky using the mean source results. Additionally, scientific studies of variability can be carried out on M 31 and the Milky Way in general.
P. Montegriffo; F. De Angeli; R. Andrae; M. Riello; E. Pancino; N. Sanna; M. Bellazzini; D. W. Evans; J. M. Carrasco; R. Sordo; G. Busso; C. Cacciari; C. Jordi; F. van Leeuwen; A. Vallenari; G. Altavilla; M. A. Barstow; A. G. A. Brown; P. W. Burgess; M. Castellani; S. Cowell; M. Davidson; F. De Luise; L. Delchambre; C. Diener; C. Fabricius; Y. Frémat; M. Fouesneau; G. Gilmore; G. Giuffrida; N. C. Hambly; D. L. Harrison; S. L. Hidalgo; S. T. Hodgkin; G. Holland; S. Marinoni; P. Osborne; C. Pagani; L. Palaversa; A. M. Piersimoni; L. Pulone; S. Ragaini; M. Rainer; P. J. Richards; N. Rowell; D. Ruz-Mieres; L. M. Sarro; N. A. Walton; A. Yoldas
Astronomy and Astrophysics · DOI ↗
Context.Gaia Data Release 3 contains astrometry and photometry results for about 1.8 billion sources based on observations collected by the European Space Agency (ESA) Gaia satellite during the first 34 months of its operational phase (the same period covered by Gaia early Data Release 3; Gaia EDR3). Low-resolution spectra for 220 million sources are one of the important new data products included in this release. Aims. In this paper, we focus on the external calibration of low-resolution spectroscopic content, describing the input data, algorithms, data processing, and the validation of the results. Particular attention is given to the quality of the data and to a number of features that users may need to take into account to make the best use of the catalogue. Methods. We calibrated an instrument model to relate mean Gaia spectra to the corresponding spectral energy distributions (SEDs) using an extended set of calibrators: this includes modelling of the instrument dispersion relation, transmission, and line spread functions. Optimisation of the model is achieved through total least-squares regression, accounting for errors in Gaia and external spectra. Results. The resulting instrument model can be used for forward modelling of Gaia spectra or for inverse modelling of externally calibrated spectra in absolute flux units. Conclusions. The absolute calibration derived in this paper provides an essential ingredient for users of BP / RP spectra. It allows users to connect BP / RP spectra to absolute fluxes and physical wavelengths.
L. Galluccio; Marco Delbò; F. De Angeli; T. Pauwels; P. Tanga; F. Mignard; A. Cellino; A. G. A. Brown; K. Muinonen; Antti Penttilä; et al.
Astronomy and Astrophysics · DOI ↗
Context. The Gaia mission of the European Space Agency (ESA) has been routinely observing Solar System objects (SSOs) since the beginning of its operations in August 2014. The Gaia data release three (DR3) includes, for the first time, the mean reflectance spectra of a selected sample of 60 518 SSOs, primarily asteroids, observed between August 5, 2014, and May 28, 2017. Each reflectance spectrum was derived from measurements obtained by means of the Blue and Red photometers (BP/RP), which were binned in 16 discrete wavelength bands. For every spectrum, the DR3 also contains additional information about the data quality for each band. Aims. We describe the processing of the Gaia spectral data of SSOs, explaining both the criteria used to select the subset of asteroid spectra published in Gaia DR3, and the different steps of our internal validation procedures. In order to further assess the quality of Gaia SSO reflectance spectra, we carried out external validation against SSO reflectance spectra obtained from ground-based and space-borne telescopes and available in the literature; we present our validation approach. Methods. For each selected SSO, an epoch reflectance was computed by dividing the calibrated spectrum observed by the BP/RP at each transit on the focal plane by the mean spectrum of a solar analogue. The latter was obtained by averaging the Gaia spectral measurements of a selected sample of stars known to have very similar spectra to that of the Sun. Finally, a mean of the epoch reflectance spectra was calculated in 16 spectral bands for each SSO. Results.Gaia SSO reflectance spectra are in general agreement with those obtained from a ground-based spectroscopic campaign specifically designed to cover the same spectral interval as Gaia and mimic the illumination and observing geometry characterising Gaia SSO observations. In addition, the agreement between Gaia mean reflectance spectra and those available in the literature is good for bright SSOs, regardless of their taxonomic spectral class. We identify an increase in the spectral slope of S-type SSOs with increasing phase angle. Moreover, we show that the spectral slope increases and the depth of the 1 μm absorption band decreases for increasing ages of S-type asteroid families. The latter can be interpreted as proof of progressive ageing of S-type asteroid surfaces due to their exposure to space weathering effects.
A. Panahi; Tsevi Mazeh; S. Zucker; David W. Latham; Karen A. Collins; L. Rimoldini; D. W. Evans; L. Eyer
Astronomy and Astrophysics · DOI ↗
Context. The TESS team periodically issues a new list of transiting exoplanet candidates based on the analysis of the accumulating light curves obtained by the satellite. The list includes the estimated epochs, periods, and durations of the potential transits. As the point spread function (PSF) of TESS is relatively wide, follow-up photometric observations at higher spatial resolution are required in order to exclude apparent transits that are actually blended background eclipsing binaries (BEBs). Aims. The Gaia space mission, with its growing database of epoch photometry and high angular resolution, enables the production of distinct light curves for all sources included in the TESS PSF, up to the limiting magnitude of Gaia . This paper reports the results of an ongoing Gaia -TESS collaboration that uses the Gaia photometry to facilitate the identification of BEB candidates and even to confirm on-target candidates in some cases. Methods. We inspected the Gaia photometry of the individual sources included in the TESS PSF, searching for periodic dimming events compatible with their ephemerides and uncertainties, as published by TESS. The performance of the search depends mainly on the number of Gaia measurements during transit and their precision. Results. Since February 2021, the collaboration has been able to confirm 126 on-target candidates and exclude 124 as BEBs. Since June 2021, when our search methodology matured, we have been able to identify on the order of 5% as on-target candidates and another 5% as BEBs. Conclusions. This synergistic approach is combining the complementary capabilities of two of the astronomical space missions of NASA and ESA. It serves to optimize the process of detecting new planets by making better use of the resources of the astronomical community.
Rokas Žemaitis; A. M. N. Ferguson; Sakurako Okamoto; Jean‐Charles Cuillandre; Connor Stone; N. Arimoto; M. J. Irwin
Monthly Notices of the Royal Astronomical Society · DOI ↗
ABSTRACT We present the discovery of a giant tidal tail of stars associated with F8D1, the closest known example of an ultra-diffuse galaxy (UDG). F8D1 sits in a region of the sky heavily contaminated by Galactic cirrus and has been poorly studied since its discovery two decades ago. The tidal feature was revealed in a deep map of resolved red giant branch stars constructed using data from our Subaru Hyper Suprime-Cam survey of the M81 Group. It has an average surface brightness of μg ∼ 32 mag arcsec−2 and can be traced for over a degree on the sky (60 kpc at the distance of F8D1) with our current imagery. We revisit the main body properties of F8D1 using deep multiband imagery acquired with MegaCam on CFHT and measure effective radii of 1.7–1.9 kpc, central surface brightnesses of 24.7–25.7 mag, and a stellar mass of ∼7 × 107M⊙. Assuming a symmetric feature on the other side of the galaxy, we calculate that 30–36 per cent of F8D1’s present-day luminosity is contained in the tail. We argue that the most likely origin of F8D1’s disruption is a recent close passage to M81, which would have stripped its gas and quenched its star formation. As the only UDG that has so far been studied to such faint surface brightness depths, the unveiling of F8D1’s tidal disruption is important. It leaves open the possibility that many other UDGs could be the result of similar processes, with the most telling signatures of this lurking below current detection limits.
P. B. Kuzma; A. M. N. Ferguson; Anna Lisa Varri; M. J. Irwin; Edouard J. Bernard; Eline Tolstoy; Jorge Peñarrubia; D. B. Zucker
Monthly Notices of the Royal Astronomical Society · DOI ↗
ABSTRACT The tidal tails of Palomar 5 (Pal 5) have been the focus of many spectroscopic studies in an attempt to identify individual stars lying along the stream and characterize their kinematics. The well-studied trailing tail has been explored out to a distance of 15○ from the cluster centre, while less than 4° have been examined along the leading tail. In this paper, we present results of a spectroscopic study of two fields along the leading tail that we have observed with the AAOmega spectrograph on the Anglo-Australian telescope. One of these fields lies roughly 7○ along the leading tail, beyond what has been previously been explored spectroscopically. Combining our measurements of kinematics and line strengths with Pan-STARRS1 photometric data and Gaia EDR3 astrometry, we adopt a probabilistic approach to identify 16 stars with a high probability of belonging to the Pal 5 stream. Eight of these stars lie in the outermost field and their sky positions confirm the presence of ‘fanning’ in the leading arm. We also revisit previously published radial velocity studies and incorporate Gaia EDR3 astrometry to remove interloping field stars. With a final sample of 109 bona fide Pal 5 cluster and tidal stream stars, we characterize the 3D kinematics along the the full extent of the system. We provide this catalogue for future modeling work.
R. Andrae; M. Fouesneau; R. Sordo; C. A. L. Bailer-Jones; T. E. Dharmawardena; J. Rybizki; F. De Angeli; H. E. P. Lindstrøm; D. J. Marshall; R. Drimmel; et al.
Espacio Tiempo y Forma Serie I Prehistoria y Arqueología · DOI ↗
We present the General Stellar Parameterizer from Photometry (GSP-Phot), which is part of the astrophysical parameters inference system (Apsis). GSP-Phot is designed to produce a homogeneous catalogue of parameters for hundreds of millions of single non-variable stars based on their astrometry, photometry, and low-resolution BP/RP spectra. These parameters are effective temperature, surface gravity, metallicity, absolute $M_G$ magnitude, radius, distance, and extinction for each star. GSP-Phot uses a Bayesian forward-modelling approach to simultaneously fit the BP/RP spectrum, parallax, and apparent $G$ magnitude. A major design feature of GSP-Phot is the use of the apparent flux levels of BP/RP spectra to derive, in combination with isochrone models, tight observational constraints on radii and distances. We carefully validate the uncertainty estimates by exploiting repeat Gaia observations of the same source. The data release includes GSP-Phot results for 471 million sources with $G&lt;19$. Typical differences to literature values are 110 K for $T_{\rm eff}$ and 0.2-0.25 for $\log g$, but these depend strongly on data quality. In particular, GSP-Phot results are significantly better for stars with good parallax measurements ($\varpi/σ_varpi&gt;20$), mostly within 2kpc. Metallicity estimates exhibit substantial biases compared to literature values and are only useful at a qualitative level. However, we provide an empirical calibration of our metallicity estimates that largely removes these biases. Extinctions $A_0$ and $A_{\rm BP}$ show typical differences from reference values of 0.07-0.09 mag. MCMC samples of the parameters are also available for 95% of the sources. GSP-Phot provides a homogeneous catalogue of stellar parameters, distances, and extinctions that can be used for various purposes, such as sample selections (OB stars, red giants, solar analogues etc.).
F. De Angeli
Zenodo (CERN European Organization for Nuclear Research) · DOI ↗
This XML file contains the basis function configuration adopted for the internally calibrated BP and RP spectra published in Gaia Data Release 3. The same file is included in the GaiaXPy (https://gaia-dpci.github.io/GaiaXPy-website/index.html) python package offering some useful functions to use the spectra. The content of the file and its basic usage are described in detail in Appendix C in the paper "Gaia Data Release 3: Processing and validation of BP/RP low-resolution spectral data", De Angeli, F. et al. A&amp;A (2022).
F. De Angeli
Zenodo (CERN European Organization for Nuclear Research) · DOI ↗
This XML file contains the basis function configuration adopted for the internally calibrated BP and RP spectra published in Gaia Data Release 3. The same file is included in the GaiaXPy (https://gaia-dpci.github.io/GaiaXPy-website/index.html) python package offering some useful functions to use the spectra. The content of the file and its basic usage are described in detail in Appendix C in the paper "Gaia Data Release 3: Processing and validation of BP/RP low-resolution spectral data", De Angeli, F. et al. A&amp;A (2022).
F. De Angeli
Zenodo (CERN European Organization for Nuclear Research) · DOI ↗
This dataset includes mean BP/RP spectra for about 43.6 thousand sources for which two mean spectra per source were generated using only a random selection of the available epoch spectra. More details about this dataset are given in Appendix D in the paper "Gaia Data Release 3: Processing and validation of BP/RP low-resolution spectral data", De Angeli, F., et al. A&amp;A (2022). Results obtained from this dataset are published in the same paper and in "Gaia Data Release 3: The Galaxy in your preferred colours. Synthetic photometry from Gaia low-resolution spectra", Gaia Collaboration, Montegriffo, P., et al. A&amp;A (2022).