ABSTRACT
The epoch corresponding to a redshift of z ∼ 6.5 is close to full re-ionization of the Universe, and early enough to provide an intriguing environment to observe the early stage of ...large-scale structure formation. It is also an epoch that can be used to verify the abundance of a large population of low luminosity star-forming galaxies that are deemed responsible for cosmic re-ionization. Here, we present the results of follow-up multi-object spectroscopy using OSIRIS at Gran Telescopio Canarias of 16 Ly α emitter (LAE) candidates discovered in the Subaru/XMM Newton Deep Survey. We have securely confirmed 10 LAEs with sufficient signal-to-noise ratio of the Ly α emission line. The inferred star formation rates of the confirmed LAEs are on the low side, within the range 0.9–4.7 M⊙ yr−1. However, they show relatively high Ly α rest frame equivalent widths. Finally we have shown that the mechanical energy released by the star formation episodes in these galaxies is enough to create holes in the neutral hydrogen medium such that Lyman continuum photons can escape to the intergalactic medium, thus contributing to the re-ionization of the Universe.
The all-sky PLATO input catalogue Montalto, M.; Piotto, G.; Marrese, P. M. ...
Astronomy and astrophysics (Berlin),
09/2021, Letnik:
653
Journal Article
Recenzirano
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Context.
The ESA PLAnetary Transits and Oscillations of stars (PLATO) mission will search for terrestrial planets in the habitable zone of solar-type stars. Because of telemetry limitations, PLATO ...targets need to be pre-selected.
Aims.
In this paper, we present an all sky catalogue that will be fundamental to selecting the best PLATO fields and the most promising target stars, deriving their basic parameters, analysing the instrumental performances, and then planing and optimising follow-up observations. This catalogue also represents a valuable resource for the general definition of stellar samples optimised for the search of transiting planets.
Methods.
We used
Gaia
Data Release 2 astrometry and photometry and 3D maps of the local interstellar medium to isolate FGK (
V
≤ 13) and M (
V
≤ 16) dwarfs and subgiant stars.
Results.
We present the first public release of the all-sky PLATO input catalogue (asPIC1.1) containing a total of 2 675 539 stars including 2 378 177 FGK dwarfs and subgiants and 297 362 M dwarfs. The median distance in our sample is 428 pc for FGK stars and 146 pc for M dwarfs, respectively. We derived the reddening of our targets and developed an algorithm to estimate stellar fundamental parameters (
T
eff
, radius, mass) from astrometric and photometric measurements.
Conclusions.
We show that the overall (internal+external) uncertainties on the stellar parameter determined in the present study are ∼230 K (4%) for the effective temperatures, ∼0.1
R
⊙
(9%) for the stellar radii, and ∼0.1
M
⊙
(11%) for the stellar mass. We release a special target list containing all known planet hosts cross-matched with our catalogue.
The X-ray Integral Field Unit (X-IFU) of the Advanced Telescope for High-ENergy Astrophysics (Athena) large-scale mission of ESA will provide spatially resolved high-resolution X-ray spectroscopy ...from 0.2 to 12 keV, with 5
″
pixels over a field of view of 5 arc minute equivalent diameter and a spectral resolution of 2.5 eV (FWHM) up to 7 keV. The core scientific objectives of Athena drive the main performance parameters of the X-IFU. We present the current reference configuration of the X-IFU, and the key issues driving the design of the instrument.
Is the Bremer Deep Field reionized, at z ∼ 7? Rodríguez Espinosa, J M; Mas-Hesse, J M; Calvi, R
Monthly notices of the Royal Astronomical Society,
05/2021, Letnik:
503, Številka:
3
Journal Article
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ABSTRACT
We show herein that the population of star-forming galaxies in the Bremer Deep Field (BDF) has enough ionizing power to form two large ionized bubbles that could be in the process of merging ...into a large one with a volume of 14 000 cMpc3. The sources identified in the BDF have been completed with a set of expected low-luminosity sources at z ∼ 7. We have estimated the number of ionizing photons per second produced by the different star-forming galaxies in the BDF. This number has been compared with the number that would be required to ionize the bubbles around the two overdense regions. We have used, as reference, ionizing emissivities derived from the AMIGA (Analytic Model of Intergalactic-medium and Galaxies) cosmological evolutionary model. We find that even using the most conservative estimates, with a Lyman continuum escape fraction of 10${{\ \rm per\ cent}}$, the two regions we have defined within the BDF would be reionized. Assuming more realistic estimates of the ionizing photon production efficiency, both bubbles would be in the process of merging into a large reionized bubble, such as those that through percolation completed the reionization of the Universe by z = 6. The rather small values of the escape fraction required to reionize the BDF are compatible with the low fraction of faint Ly α emitters identified in the BDF. Finally, we confirm that the low-luminosity sources represent indeed the main contributors to the BDF ionizing photon production.
In this paper we report the second soft gamma-ray source catalog obtained with the IBIS/ISGRI gamma-ray imager on board the INTEGRAL satellite. The scientific data set is based on more than 10 Ms of ...high-quality observations performed during the first 2 years of Core Program and public IBIS/ISGRI observations, and covers ~50% of the whole sky. The main aim of the first survey was to scan systematically, for the first time at energies above 20 keV, the whole Galactic plane to achieve a limiting sensitivity of ~1 mcrab in the central radian. The target of the second year of the INTEGRAL mission lifetime was to expand as much as possible our knowledge of the soft gamma-ray sky, with the same limiting sensitivity, to at least 50% of the whole sky, mainly by including a substantial coverage of extragalactic fields. This catalog comprises more than 200 high-energy sources detected in the energy range 20-100 keV, including new transients not active during the first year of operation, faint persistent objects revealed with longer exposure time, and several Galactic and extragalactic sources in sky regions not observed in the first survey. The mean position error for all the sources detected with significance above 10 ? is ~40", enough to identify most of them with a known X-ray counterpart and to unveil the nature of most of the strongly absorbed ones, even though they are very difficult to detect in X-rays. Based on observations with INTEGRAL, an ESA project with instruments and science data center funded by ESA member states (especially the PI countries: Denmark, France, Germany, Italy, Switzerland, Spain), Czech Republic, and Poland, and with the participation of Russia and the USA.
Abstract As the nearest confirmed Lyman continuum (LyC) emitter, Haro 11 is an exceptional laboratory for studying LyC escape processes crucial to cosmic reionization. Our new Hubble Space ...Telescope/Cosmic Origins Spectrograph G130M/1055 observations of its three star-forming knots now reveal that the observed LyC originates in Knots B and C, with 903–912 Å luminosities of 1.9 ± 1.5 × 10 40 erg s −1 and 0.9 ± 0.7 × 10 40 erg s −1 , respectively. We derive local escape fractions f esc,912 = 3.4% ± 2.9% and 5.1% ± 4.3% for Knots B and C, respectively. Our Starburst99 modeling shows dominant populations on the order of ∼1–4 Myr and 1–2 × 10 7 M ⊙ in each knot, with the youngest population in Knot B. Thus, the knot with the strongest LyC detection has the highest LyC production. However, LyC escape is likely less efficient in Knot B than in Knot C due to higher neutral gas covering. Our results therefore stress the importance of the intrinsic ionizing luminosity, and not just the escape fraction, for LyC detection. Similarly, the Ly α escape fraction does not consistently correlate with LyC flux, nor do narrow Ly α red peaks. High observed Ly α luminosity and low Ly α peak velocity separation, however, do correlate with higher LyC escape. Another insight comes from the undetected Knot A, which drives the Green Pea properties of Haro 11. Its density-bounded conditions suggest highly anisotropic LyC escape. Finally, both of the LyC-leaking Knots, B and C, host ultraluminous X-ray sources (ULXs). While stars strongly dominate over the ULXs in LyC emission, this intriguing coincidence underscores the importance of unveiling the role of accretors in LyC escape and reionization.
Context. We present a multiwavelength analysis of the simultaneous optical and X-ray light curves of the microquasar V404 Cyg during the June 2015 outburst. Aims. We have performed a comprehensive ...analysis of all the INTEGRAL/IBIS, JEM–X, and OMC observations during the brightest epoch of the outburst, along with complementary NuSTAR, AAVSO, and VSNET data, to examine the timing relationship between the simultaneous optical and X-ray light curves, in order to understand the emission mechanisms and physical locations. Methods. We have identified all optical flares that have simultaneous X-ray observations, and performed a cross-correlation analysis to estimate the time delays between the optical and soft and hard X-ray emission. We also compared the evolution of the optical and X-ray emission with the hardness ratios. Results. We have identified several types of behaviour during the outburst. On many occasions, the optical flares occur simultaneously with X-ray flares, but at other times, positive and negative time delays between the optical and X-ray emission are measured. Conclusions. We conclude that the observed optical variability is driven by different physical mechanisms, including reprocessing of X-rays in the accretion disc and/or the companion star, interaction of the jet ejections with surrounding material or with previously ejected blobs, and synchrotron emission from the jet.
The PLATO 2.0 mission Rauer, H.; Catala, C.; Benz, W. ...
Experimental astronomy,
11/2014, Letnik:
38, Številka:
1-2
Journal Article, Web Resource
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PLATO 2.0 has recently been selected for ESA’s M3 launch opportunity (2022/24). Providing accurate key planet parameters (radius, mass, density and age) in statistical numbers, it addresses ...fundamental questions such as: How do planetary systems form and evolve? Are there other systems with planets like ours, including potentially habitable planets? The PLATO 2.0 instrument consists of 34 small aperture telescopes (32 with 25 s readout cadence and 2 with 2.5 s candence) providing a wide field-of-view (2232 deg
2
) and a large photometric magnitude range (4–16 mag). It focusses on bright (4–11 mag) stars in wide fields to detect and characterize planets down to Earth-size by photometric transits, whose masses can then be determined by ground-based radial-velocity follow-up measurements. Asteroseismology will be performed for these bright stars to obtain highly accurate stellar parameters, including masses and ages. The combination of bright targets and asteroseismology results in high accuracy for the bulk planet parameters: 2 %, 4–10 % and 10 % for planet radii, masses and ages, respectively. The planned baseline observing strategy includes two long pointings (2–3 years) to detect and bulk characterize planets reaching into the habitable zone (HZ) of solar-like stars and an additional step-and-stare phase to cover in total about 50 % of the sky. PLATO 2.0 will observe up to 1,000,000 stars and detect and characterize hundreds of small planets, and thousands of planets in the Neptune to gas giant regime out to the HZ. It will therefore provide the first large-scale catalogue of bulk characterized planets with accurate radii, masses, mean densities and ages. This catalogue will include terrestrial planets at intermediate orbital distances, where surface temperatures are moderate. Coverage of this parameter range with statistical numbers of bulk characterized planets is unique to PLATO 2.0. The PLATO 2.0 catalogue allows us to e.g.: - complete our knowledge of planet diversity for low-mass objects, - correlate the planet mean density-orbital distance distribution with predictions from planet formation theories,- constrain the influence of planet migration and scattering on the architecture of multiple systems, and - specify how planet and system parameters change with host star characteristics, such as type, metallicity and age. The catalogue will allow us to study planets and planetary systems at different evolutionary phases. It will further provide a census for small, low-mass planets. This will serve to identify objects which retained their primordial hydrogen atmosphere and in general the typical characteristics of planets in such low-mass, low-density range. Planets detected by PLATO 2.0 will orbit bright stars and many of them will be targets for future atmosphere spectroscopy exploring their atmosphere. Furthermore, the mission has the potential to detect exomoons, planetary rings, binary and Trojan planets. The planetary science possible with PLATO 2.0 is complemented by its impact on stellar and galactic science via asteroseismology as well as light curves of all kinds of variable stars, together with observations of stellar clusters of different ages. This will allow us to improve stellar models and study stellar activity. A large number of well-known ages from red giant stars will probe the structure and evolution of our Galaxy. Asteroseismic ages of bright stars for different phases of stellar evolution allow calibrating stellar age-rotation relationships. Together with the results of ESA’s Gaia mission, the results of PLATO 2.0 will provide a huge legacy to planetary, stellar and galactic science.
ABSTRACT
We show herein that a proto-cluster of Ly α emitting galaxies, spectroscopically confirmed at redshift 6.5, produces a remarkable number of ionizing continuum photons. We start from the Ly α ...fluxes measured in the spectra of the sources detected spectroscopically. From these fluxes, we derive the ionizing emissivity of continuum photons of the protocluster, which we compare with the ionizing emissivity required to reionize the protocluster volume. We find that the sources in the protocluster are capable of ionizing a large bubble, indeed larger than the volume occupied by the protocluster. For various calculations, we have used the model AMIGA, in particular to derive the emissivity of the Lyman continuum photons required to maintain the observed volume ionized. Besides, we have assumed the ionizing photons escape fraction given by AMIGA at this redshift.
Context.
Identifying very high-redshift galaxies is crucial for understanding the formation and evolution of galaxies. However, many questions still remain, and the uncertainty on the epoch of ...reionization is large. In this approach, some models allow a double-reionization scenario, although the number of confirmed detections at very high
z
is still too low to serve as observational proof.
Aims.
The main goal of this project is studying whether we can search for Lyman-
α
emitters (LAEs) at
z
∼ 9 using a narrow-band (NB) filter that was specifically designed by our team and was built for this experiment.
Methods.
We used the NB technique to select candidates by measuring the flux excess due to the Ly
α
emission. The observations were taken with an NB filter (full width at half minimum of 11 nm and central wavelength
λ
c
= 1.257 μm) and the CIRCE near-infrared camera for the Gran Telescopio Canarias. We describe a data reduction procedure that was especially optimized to minimize instrumental effects. With a total exposure time of 18.3 h, the final NB image covers an area of ∼6.7 arcmin
2
, which corresponds to a comoving volume of 1.1 × 10
3
Mpc
3
at
z
= 9.3.
Results.
We pushed the source detection to its limit, which allows us to analyze an initial sample of 97 objects. We detail the different criteria we applied to select the candidates. The criteria included visual verifications in different photometric bands. None of the objects resembled a reliable LAE, however, and we found no robust candidate down to an emission-line flux of 2.9 × 10
−16
erg s
−1
cm
−2
, which corresponds to a Ly
α
luminosity limit of 3 × 10
44
erg s
−1
. We derive an upper limit on the Ly
α
luminosity function at
z
∼ 9 that agrees well with previous constraints. We conclude that deeper and wider surveys are needed to study the LAE population at the cosmic dawn.
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