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Gaia Data Release 3. Stellar multiplicity, a teaser for the hidden treasure
Get PDFContext. The Gaia DR3 catalogue contains, for the first time, about 800 000 solutions with either orbital elements or trend parameters for astrometric, spectroscopic, and eclipsing binaries, and combinations of these three. Aims: With this paper, we aim to illustrate the huge potential of this large non-single-star catalogue. Methods: Using the orbital solutions and models of the binaries, we have built a catalogue of tens of thousands of stellar masses or lower limits thereof, some with consistent flux ratios. Properties concerning the completeness of the binary catalogues are discussed, statistical features of the orbital elements are explained, and a comparison with other catalogues is performed. Results: Illustrative applications are proposed for binaries across the Hertzsprung-Russell Diagram (HRD). Binarity is studied in the giant branch and a search for genuine spectroscopic binaries among long-period variables is performed. The discovery of new EL CVn systems illustrates the potential of combining variability and binarity catalogues. Potential compact object companions are presented, mainly white dwarf companions or double degenerates, but one candidate neutron star is also found. Towards the bottom of the main sequence, the orbits of previously suspected binary ultracool dwarfs are determined and new candidate binaries are discovered. The long awaited contribution of Gaia to the analysis of the substellar regime shows the brown dwarf desert around solar-type stars using true rather than minimum masses, and provides new important constraints on the occurrence rates of substellar companions to M dwarfs. Several dozen new exoplanets are proposed, including two with validated orbital solutions and one super-Jupiter orbiting a white dwarf, all being candidates requiring confirmation. Besides binarity, higher order multiple systems are also found. Conclusions: By increasing the number of known binary orbits by more than one order of magnitude, Gaia DR3 will provide a rich reservoir of dynamical masses and an important contribution to the analysis of stellar multiplicity...
CEERS Epoch 1 NIRCam Imaging: Reduction Methods and Simulations Enabling Early JWST Science Results
No full textWe present the data release and data reduction process for the Epoch 1 NIRCam observations for the Cosmic Evolution Early Release Science Survey (CEERS). These data consist of NIRCam imaging in six broadband filters (F115W, F150W, F200W, F277W, F356W and F444W) and one medium-band filter (F410M) over four pointings, obtained in parallel with primary CEERS MIRI observations. We reduced the NIRCam imaging with the JWST Calibration Pipeline, with custom modifications and reduction steps designed to address additional features and challenges with the data. Here we provide a detailed description of each step in our reduction and a discussion of future expected improvements. Our reduction process includes corrections for known prelaunch issues such as 1/f noise, as well as in-flight issues including snowballs, wisps, and astrometric alignment. Many of our custom reduction processes were first developed with prelaunch simulated NIRCam imaging over the full 10 CEERS NIRCam pointings. We present a description of the creation and reduction of this simulated data set in the Appendix. We provide mosaics of the real images in a public release, as well as our reduction scripts with detailed explanations to allow users to reproduce our final data products. These represent one of the first official public data sets released from the Directors Discretionary Early Release Science (DD-ERS) program
Magnetic reconnection as an erosion mechanism for magnetic switchbacks
Get PDFMagnetic switchbacks are localised polarity reversals in the radial component
of the heliospheric magnetic field. Observations from Parker Solar Probe (PSP)
have shown that they are a prevalent feature of the near-Sun solar wind.
However, observations of switchbacks at 1 au and beyond are less frequent,
suggesting that these structures evolve and potentially erode through yet-to-be
identified mechanisms as they propagate away from the Sun. We analyse magnetic
field and plasma data from the Magnetometer and Solar Wind Analyser instruments
aboard Solar Orbiter between 10 August and 30 August 2021. During this period,
the spacecraft was 0.6 to 0.7 au from the Sun. We identify three instances of
reconnection occurring at the trailing edge of magnetic switchbacks, with
properties consistent with existing models describing reconnection in the solar
wind. Using hodographs and Walen analysis methods, we test for rotational
discontinuities (RDs) in the magnetic field and reconnection-associated
outflows at the boundaries of the identified switchback structures. Based on
these observations, we propose a scenario through which reconnection can erode
a switchback and we estimate the timescales over which this occurs. For our
events, the erosion timescales are much shorter than the expansion timescale
and thus, the complete erosion of all three observed switchbacks would occur
well before they reach 1 au. Furthermore, we find that the spatial scale of
these switchbacks would be considerably larger than is typically observed in
the inner heliosphere if the onset of reconnection occurs close to the Sun.
Hence, our results suggest that the onset of reconnection must occur during
transport in the solar wind in our cases. These results suggest that
reconnection can contribute to the erosion of switchbacks and may explain the
relative rarity of switchback observations at 1 au
Gaia Data Release 3. Astrometric orbit determination with Markov chain Monte Carlo and genetic algorithms: Systems with stellar, sub-stellar, and planetary mass companions
Get PDFContext. The astrometric discovery of sub-stellar mass companions orbiting stars is exceedingly hard due to the required sub-milliarcsecond precision, limiting the application of this technique to only a few instruments on a target-per-target basis and to the global astrometry space missions HIPPARCOS and Gaia. The third Gaia data release (Gaia DR3) includes the first Gaia astrometric orbital solutions whose sensitivity in terms of estimated companion mass extends down to the planetary-mass regime. Aims: We present the contribution of the exoplanet pipeline to the Gaia DR3 sample of astrometric orbital solutions by describing the methods used for fitting the orbits, the identification of significant solutions, and their validation. We then present an overview of the statistical properties of the solution parameters. Methods: Using both a Markov chain Monte Carlo and a genetic algorithm, we fitted the 34 months of Gaia DR3 astrometric time series with a single Keplerian astrometric-orbit model that had 12 free parameters and an additional jitter term, and retained the solutions with the lowest χ2. Verification and validation steps were taken using significance tests, internal consistency checks using the Gaia radial velocity measurements (when available), as well as literature radial velocity and astrometric data, leading to a subset of candidates that were labelled "validated". Results: We determined astrometric-orbit solutions for 1162 sources, and 198 solutions were assigned the "Validated" label. Precise companion-mass estimates require external information and are presented elsewhere. To broadly categorise the different mass regimes in this paper, we use the pseudo-companion mass M̃c assuming a solar-mass host and define three solution groups: 17 (9 validated) solutions with companions in the planetary-mass regime (M̃c J), 52 (29 validated) in the brown dwarf regime (20 MJ ≤ M̃c ≤ 120 MJ), and 1093 (160 validated) in the low-mass stellar companion regime (M̃c > 120 MJ). From internal and external verification and validation, we estimate the level of spurious and incorrect solutions in our sample to be ∼5% and ∼10% in the `OrbitalAlternative' and `OrbitalTargetedSearch' candidate sample, respectively. Conclusions: We demonstrate that Gaia is able to confirm and sometimes refine the orbits of known orbital companions and to identify new candidates, providing us with a positive outlook for the expected harvest from the full mission data in future data releases. Tables refsols.dat, bd-18113.dat, 46_10046.dat, gj812a.dat, gj9732.dat, hd26596.dat, hd40503.dat, hd68638.dat, hd89010.dat, hd134237.dat, hd183162.dat, hip9095.dat, and toi-288.dat are only available at the CDS via anonymous ftp to cdsarc.cds.unistra.fr (ftp://130.79.128.5) or via https://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/674/A10..
Solar Observations by Angelo Secchi. I. Digitization of Original Documents and Analysis of Group Numbers over the Period of 1853-1878
Get PDFAngelo Secchi, an Italian Jesuit and prominent scientist of the 19th century, and one of the founders of modern astrophysics, observed the Sun regularly at the Collegio Romano in Rome, Italy, for more than 25 yr. Results from his observations are reported in articles published in the scientific journals of the time, as well as in drawings and personal notebooks that are stored in the historical archive of the Istituto Nazionale di Astrofisica Osservatorio Astronomico di Roma. The latter material, which reports solar observations performed from 1853-1878, includes original documents from Secchi and from a few of his close collaborators. The above unique material has recently been digitized for preservation purposes and for allowing the scientific exploitation of data not easily accessible so far. A total of more than 5400 digital images have been produced. Here we present the archival material and the new digital data derived from it. We also present results obtained from our primary analysis of the new digital data. In particular, we produced new measurements of the group number from 1853-1878, which will be available for future recalibration of the group number series
Ejecta from the DART-produced active asteroid Dimorphos
Get PDFSome active asteroids have been proposed to be formed as a result of impact events1. Because active asteroids are generally discovered by chance only after their tails have fully formed, the process of how impact ejecta evolve into a tail has, to our knowledge, not been directly observed. The Double Asteroid Redirection Test (DART) mission of NASA2, in addition to having successfully changed the orbital period of Dimorphos3, demonstrated the activation process of an asteroid resulting from an impact under precisely known conditions. Here we report the observations of the DART impact ejecta with the Hubble Space Telescope from impact time T + 15 min to T + 18.5 days at spatial resolutions of around 2.1 km per pixel. Our observations reveal the complex evolution of the ejecta, which are first dominated by the gravitational interaction between the Didymos binary system and the ejected dust and subsequently by solar radiation pressure. The lowest-speed ejecta dispersed through a sustained tail that had a consistent morphology with previously observed asteroid tails thought to be produced by an impact4,5. The evolution of the ejecta after the controlled impact experiment of DART thus provides a framework for understanding the fundamental mechanisms that act on asteroids disrupted by a natural impact1,6
Early Spectroscopy and Dense Circumstellar Medium Interaction in SN 2023ixf
Get PDFWe present the optical spectroscopic evolution of SN 2023ixf seen in subnight cadence spectra from 1.18 to 15 days after explosion. We identify high-ionization emission features, signatures of interaction with material surrounding the progenitor star, that fade over the first 7 days, with rapid evolution between spectra observed within the same night. We compare the emission lines present and their relative strength to those of other supernovae with early interaction, finding a close match to SN 2020pni and SN 2017ahn in the first spectrum and SN 2014G at later epochs. To physically interpret our observations, we compare them to CMFGEN models with confined, dense circumstellar material around a red supergiant (RSG) progenitor from the literature. We find that very few models reproduce the blended N III (λλ4634.0,4640.6)/C III (λλ4647.5,4650.0) emission lines observed in the first few spectra and their rapid disappearance thereafter, making this a unique diagnostic. From the best models, we find a mass-loss rate of 10-3-10-2 M ⊙ yr-1, which far exceeds the mass-loss rate for any steady wind, especially for an RSG in the initial mass range of the detected progenitor. These mass-loss rates are, however, similar to rates inferred for other supernovae with early circumstellar interaction. Using the phase when the narrow emission features disappear, we calculate an outer dense radius of circumstellar material R CSM,out ≈ 5 × 1014 cm, and a mean circumstellar material density of ρ = 5.6 × 10-14 g cm-3. This is consistent with the lower limit on the outer radius of the circumstellar material we calculate from the peak Hα emission flux, R CSM,out ≳ 9 × 1013 cm
Geological, compositional and crystallinity analysis of the Melkart impact crater, Ganymede
Get PDFIn this work, we analyze the ∼103 km-diameter Melkart impact crater on the surface of Ganymede, which is a ∼ 103 km impact crater located at the boundary between the two main geological units of the satellite, the light and dark terrains. Such crater is covered both by Galileo SSI and NIMS datasets allowing inference of any possible correlation between its geology and composition, as well as to investigate the evolution of the substrate units. We provide a geomorphological characterization of the crater by creating a high-resolution geological map, investigating the DTM and performing a strain analysis to infer its deformation. We find that the Melkart dome underwent strike-slip deformation with right-lateral kinematics. Moreover, this crater is a low strain end member with subtle deformation, which has been formed in an area of gradual transition between light and dark terrains. The results obtained through band depth and crystallinity maps of the study area do not reflect the evolutionary history of the crater, instead, they are representative of the different geological terrains affecting the subsurface of Melkart. Such result implies that the possible compositional differences between the crater's units might have been obliterated through time. Our analysis supports the interpretation that the material constituting the substrate of the crater might be heterogeneous suggesting that: (i) the transition between the two geological units might be gradual or ii) the dark material located over the study area only represents a thin layer draping the icy crust
Is the star formation rate in z ∼ 6 quasars overestimated?
No full textThe large total infrared (TIR) luminosities () observed in quasars are generally converted into
high star formation rates ( yr) of their host
galaxies. However, these estimates rely on the assumption that dust heating is
dominated by stellar radiation, neglecting the contribution from the central
Active Galactic Nuclei (AGN). We test the validity of this assumption by
combining cosmological hydrodynamic simulations with radiative transfer
calculations. We find that, when AGN radiation is included in the simulations,
the mass (luminosity)-weighted dust temperature in the host galaxies increases
from K ( K) to K ( K),
suggesting that AGN effectively heat the bulk of dust in the host galaxy. We
compute the AGN-host galaxy from the synthetic spectral energy
distribution by using standard relations, and compare the
results with the "true" values in the simulations. We find that the is
overestimated by a factor of () for AGN bolometric
luminosities of (), implying that the star formation rates of quasars can be
overestimated by over an order of magnitude
A New Galaxy Cluster Merger Capable of Probing Dark Matter: A56
No full textWe report the discovery of a binary galaxy cluster merger via a search of the redMaPPer optical cluster catalog, with a projected separation of 535 kpc between the brightest cluster galaxies (BCGs). Archival XMM-Newton spectro-imaging reveals a gas peak between the BCGs, suggesting a recent pericenter passage. We conduct a galaxy redshift survey to quantify the line-of-sight velocity difference (153 ± 281 km s-1) between the two subclusters. We present weak-lensing mass maps from archival Hubble Space Telescope Advanced Camera for Surveys (HST/ACS) imaging, revealing masses of M 200 = 4.5 ± 0.8 × 1014 and 2.8 ± 0.7 × 1014 M ⊙ associated with the southern and northern galaxy subclusters, respectively. We also present deep GMRT 650 MHz data revealing extended emission, 420 kpc long, which may be an active galactic nucleus (AGN) tail but is potentially also a candidate radio relic. We draw from cosmological n-body simulations to find analog systems, which imply that this system is observed fairly soon (60-271 Myr) after pericenter, and that the subcluster separation vector is within 22° of the plane of the sky, making it suitable for an estimate of the dark matter scattering cross section. We find cm2 g-1, suggesting that further study of this system could support interestingly tight constraints...