scholarly journals On the detection of supermassive primordial stars – II. Blue supergiants

2019 ◽  
Vol 488 (3) ◽  
pp. 3995-4003 ◽  
Author(s):  
Marco Surace ◽  
Erik Zackrisson ◽  
Daniel J Whalen ◽  
Tilman Hartwig ◽  
S C O Glover ◽  
...  
Keyword(s):  
Gravitational Lensing ◽  
Near Infrared ◽  
Detection Limits ◽  
Wide Field ◽  
Spectral Features ◽  
Field Surveys ◽  
Space Telescope ◽  
Surface Temperatures ◽  
James Webb Space Telescope ◽  
The Universe

ABSTRACT Supermassive primordial stars in hot, atomically cooling haloes at z ∼ 15–20 may have given birth to the first quasars in the Universe. Most simulations of these rapidly accreting stars suggest that they are red, cool hypergiants, but more recent models indicate that some may have been bluer and hotter, with surface temperatures of 20 000–40 000 K. These stars have spectral features that are quite distinct from those of cooler stars and may have different detection limits in the near-infrared today. Here, we present spectra and AB magnitudes for hot, blue supermassive primordial stars calculated with the tlusty and cloudy codes. We find that photometric detections of these stars by the James Webb Space Telescope will be limited to z ≲ 10–12, lower redshifts than those at which red stars can be found, because of quenching by their accretion envelopes. With moderate gravitational lensing, Euclid and the Wide-Field Infrared Space Telescope could detect blue supermassive stars out to similar redshifts in wide-field surveys.

scholarly journals Probing the faintest galaxy population at the epoch of reionization with gravitational lensing

2019 ◽  
Vol 15 (S352) ◽  
pp. 26-26
Author(s):  
Hakim Atek
Keyword(s):  
Gravitational Lensing ◽  
Hubble Space Telescope ◽  
Space Telescope ◽  
Systematic Uncertainties ◽  
James Webb Space Telescope ◽  
Exciting Opportunity ◽  
Complete Dataset ◽  
Galaxy Populations ◽  
Galaxy Population ◽  
The Universe

AbstractUltra-deep observations of blank fields with the Hubble Space Telescope have made important inroads in characterizing galaxy populations at redshift z = 6 – 10. Gravitational lensing by massive galaxy clusters offers a new route to identify the faintest sources at the epoch of reionization. In particular, thanks to the Hubble Frontier Fields program, we robustly pushed the detection limit down to MAB = − 15 mag at z ∼ 6. I will present the latest results based on the complete dataset of the HFF clusters and parallel fields, and their implications on the ability of galaxies to reionize the Universe. I will also discuss the results of a comprehensive end-to-end modeling effort towards constraining the systematic uncertainties of the lens models, which are currently the last hurdle before extending the UV LF to fainter luminosities. Finally, I will discuss the great discoveries awaiting combination of such cosmic lenses with the upcoming James Webb Space Telescope and the exciting opportunity to probe the turnover of the UV LF, hence the limit of the star formation process at those early epochs.

scholarly journals Radio Power from Direct-collapse Black Holes

2021 ◽  
Vol 922 (2) ◽  
pp. L39
Author(s):  
Daniel J. Whalen ◽  
Mar Mezcua ◽  
Samuel J. Patrick ◽  
Avery Meiksin ◽  
Muhammad A. Latif
Keyword(s):  
Black Holes ◽  
Near Infrared ◽  
Space Telescope ◽  
Very Large Array ◽  
Black Hole Accretion ◽  
James Webb Space Telescope ◽  
New Radio ◽  
Sky Survey ◽  
The Universe ◽  
Radio Power

Abstract Direct-collapse black holes (DCBHs) forming at z ∼ 20 are currently the leading candidates for the seeds of the first quasars, over 200 of which have now been found at z > 6. Recent studies suggest that DCBHs could be detected in the near-infrared by the James Webb Space Telescope, Euclid, and the Roman Space Telescope. However, new radio telescopes with unprecedented sensitivities such as the Square Kilometre Array (SKA) and the Next-Generation Very Large Array (ngVLA) may open another window on the properties of DCBHs in the coming decade. Here we estimate the radio flux from DCBHs at birth at z = 8–20 with several fundamental planes of black hole accretion. We find that they could be detected at z ∼ 8 by the SKA-FIN all-sky survey. Furthermore, SKA and ngVLA could discover 106–107 M ⊙ BHs out to z ∼ 20, probing the formation pathways of the first quasars in the universe.

scholarly journals All NIRspec Needs is HST/WFC3 Pre-Imaging? The Use of Milky Way Stars in WFC3 Imaging to Register NIRspec MSA Observations

2016 ◽  
Vol 05 (03) ◽  
pp. 1650008
Author(s):  
B. W. Holwerda ◽  
R. J. Bouwens ◽  
M. Trenti ◽  
M. A. Kenworthy
Keyword(s):  
Near Infrared ◽  
Hubble Space Telescope ◽  
High Redshift ◽  
Wide Field ◽  
Galactic Latitude ◽  
Space Telescope ◽  
James Webb Space Telescope ◽  
Specific Formula ◽  
The Right ◽  
Guide Star

The James Webb Space Telescope (JWST) will be an exquisite new near-infrared observatory with imaging and multi-object spectroscopy through ESA’s NIRspec instrument with its unique Micro-Shutter Array (MSA), allowing for slits to be positioned on astronomical targets by opening specific [Formula: see text]-wide micro shutter doors. To ensure proper Target Acquisition (TA), the on-sky position of the MSA needs to be verified before spectroscopic observations start. An onboard centroiding program registers the position of pre-identified guide stars in a TA image, a short pre-spectroscopy exposure without dispersion (image mode) through the MSA with all shutters open. The outstanding issue is the availability of Galactic stars in the right luminosity range for TA relative to typical high redshift targets. We explore this here using the stars and [Formula: see text] candidate galaxies identified in the source extractor catalogs of Brightest of Reionizing Galaxies survey (BoRG[z8]), a pure-parallel program with Hubble Space Telescope Wide-Field Camera 3. We find that (a) a single WFC3 field contains enough Galactic stars to satisfy the NIRspec astrometry requirement (20 milli-arcseconds), provided its and the NIRspec TA’s are [Formula: see text] AB in WFC3 [Formula: see text], (b) a single WFC3 image can therefore serve as the pre-image if need be, (c) a WFC3 mosaic and accompanying TA image satisfy the astrometry requirement at [Formula: see text] AB mag in WFC3 [Formula: see text], (d) no specific Galactic latitude requires deeper TA imaging due to a lack of Galactic stars, and (e) a depth of [Formula: see text] AB mag in WFC3 [Formula: see text] is needed if a guide star in the same MSA quadrant as a target is required. We take the example of a BoRG identified [Formula: see text] candidate galaxy and require a Galactic star within 20[Formula: see text] of it. In this case, a depth of 25.5 AB in [Formula: see text] is required (with [Formula: see text]97% confidence).

scholarly journals Search for giant planets around seven white dwarfs in the Hyades cluster with the Hubble Space Telescope

2020 ◽  
Vol 500 (3) ◽  
pp. 3920-3925
Author(s):  
Wolfgang Brandner ◽  
Hans Zinnecker ◽  
Taisiya Kopytova
Keyword(s):  
White Dwarfs ◽  
Near Infrared ◽  
Hubble Space Telescope ◽  
Infrared Camera ◽  
Detection Limits ◽  
Giant Planets ◽  
High Angular Resolution ◽  
Mass Detection ◽  
Space Telescope ◽  
Hyades Cluster

ABSTRACT Only a small number of exoplanets have been identified in stellar cluster environments. We initiated a high angular resolution direct imaging search using the Hubble Space Telescope (HST) and its Near-Infrared Camera and Multi-Object Spectrometer (NICMOS) instrument for self-luminous giant planets in orbit around seven white dwarfs in the 625 Myr old nearby (≈45 pc) Hyades cluster. The observations were obtained with Near-Infrared Camera 1 (NIC1) in the F110W and F160W filters, and encompass two HST roll angles to facilitate angular differential imaging. The difference images were searched for companion candidates, and radially averaged contrast curves were computed. Though we achieve the lowest mass detection limits yet for angular separations ≥0.5 arcsec, no planetary mass companion to any of the seven white dwarfs, whose initial main-sequence masses were >2.8 M⊙, was found. Comparison with evolutionary models yields detection limits of ≈5–7 Jupiter masses (MJup) according to one model, and between 9 and ≈12 MJup according to another model, at physical separations corresponding to initial semimajor axis of ≥5–8 au (i.e. before the mass-loss events associated with the red and asymptotic giant branch phase of the host star). The study provides further evidence that initially dense cluster environments, which included O- and B-type stars, might not be highly conducive to the formation of massive circumstellar discs, and their transformation into giant planets (with m ≥ 6 MJup and a ≥6 au). This is in agreement with radial velocity surveys for exoplanets around G- and K-type giants, which did not find any planets around stars more massive than ≈3 M⊙.

scholarly journals Substellar and low-mass dwarf identification with near-infrared imaging space observatories

2018 ◽  
Vol 620 ◽  
pp. A132 ◽  
Author(s):  
B. W. Holwerda ◽  
J. S. Bridge ◽  
R. Ryan ◽  
M. A. Kenworthy ◽  
N. Pirzkal ◽  
...  
Keyword(s):  
Near Infrared ◽  
Infrared Imaging ◽  
High Redshift ◽  
Brown Dwarfs ◽  
Wide Field ◽  
Space Telescope ◽  
Low Mass ◽  
Space Observatories ◽  
Broad Type ◽  
Selection Of

Aims. We aim to evaluate the near-infrared colors of brown dwarfs as observed with four major infrared imaging space observatories: the Hubble Space Telescope (HST), the James Webb Space Telescope (JWST), the Euclid mission, and the WFIRST telescope. Methods. We used the SPLAT SPEX/ISPEX spectroscopic library to map out the colors of the M-, L-, and T-type dwarfs. We have identified which color–color combination is optimal for identifying broad type and which single color is optimal to then identify the subtype (e.g., T0-9). We evaluated each observatory separately as well as the narrow-field (HST and JWST) and wide-field (Euclid and WFIRST) combinations. Results. The Euclid filters perform equally well as HST wide filters in discriminating between broad types of brown dwarfs. WFIRST performs similarly well, despite a wider selection of filters. However, subtyping with any combination of Euclid and WFIRST observations remains uncertain due to the lack of medium, or narrow-band filters. We argue that a medium band added to the WFIRST filter selection would greatly improve its ability to preselect brown dwarfs its imaging surveys. Conclusions. The HST filters used in high-redshift searches are close to optimal to identify broad stellar type. However, the addition of F127M to the commonly used broad filter sets would allow for unambiguous subtyping. An improvement over HST is one of two broad and medium filter combinations on JWST: pairing F140M with either F150W or F162M discriminates very well between subtypes.

scholarly journals Fracture of Be and Its Alloys - Webb Space Telescope Revisited

2021 ◽  
Author(s):  
Muhammad Musaddique Ali Rafique
Keyword(s):  
Near Infrared ◽  
Joint Venture ◽  
Coefficient Of Thermal Expansion ◽  
Infrared Range ◽  
Linear Coefficient ◽  
Space Telescope ◽  
Hexagonal Close Packed ◽  
James Webb Space Telescope ◽  
Layer Deposition ◽  
Slip Planes

NASA/ESA/CSA joint venture James Webb Space Telescope is about to be launched. It is hypothesized to operate in near-infrared range. It is also hypothesized to unveil early star formation, galaxies, and universe due to its orbit, point in orbit and orbital motion. It has been under manufacturing for over 20 years at a staggering cost of 10 billion US dollars (most expensive scientific experiment in history). Beryllium (Be) is chosen to be element for construction of its main mirrors due to its high stiffness, low density, low linear coefficient of thermal expansion (α) in cryogenics and high thermal conductivity. It is followed by gold (Au) layer deposition on its (Be) surface to enhance its sensitivity towards infrared radiation as later is hypothesized to bear superior properties. However, serious mistakes have been made in selecting this material for this application. Owing to its crystal structure (hexagonal close packed (hcp)), slip planes (basal, prismatic and pyramidal) and mechanisms of their activation, Be necessitates easy fracture at cryogenic temperature. It has anisotropic properties and prone to transverse fracture under tensile loading. Furthermore, its ductile to brittle transition temperature is very low making it entirely unsuitable for such an application. It is one of most expensive metals on planet. This study constitutes revisiting these fundamental properties and mechanisms which were entirely ignored during materials selection thus rendering whole project useless.

Detectors for the James Webb Space Telescope near infrared spectrograph (NIRSpec)

2006 ◽  
Author(s):  
Bernard J. Rauscher ◽  
Torsten Böker ◽  
Craig Cabelli ◽  
Guido De Marchi ◽  
Pierre Ferruit ◽  
...  
Keyword(s):  
Near Infrared ◽  
Space Telescope ◽  
James Webb Space Telescope

scholarly journals Properties of sub-Neptune atmospheres: TOI-270 system

2020 ◽  
Vol 495 (1) ◽  
pp. 962-970
Author(s):  
J Chouqar ◽  
Z Benkhaldoun ◽  
A Jabiri ◽  
J Lustig-Yaeger ◽  
A Soubkiou ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Signal To Noise Ratio ◽  
Spectral Features ◽  
Transmission Spectra ◽  
Infrared Transmission ◽  
Signal To Noise ◽  
Space Telescope ◽  
Molecular Features ◽  
James Webb Space Telescope ◽  
Mean Molecular Weight

ABSTRACT We investigate the potential for the James Webb Space Telescope (JWST) to detect and characterize the atmospheres of the sub-Neptunian exoplanets in the TOI-270 system. Sub-Neptunes are considered more likely to be water worlds than gas dwarfs. We model their atmospheres using three atmospheric compositions – two examples of hydrogen-dominated atmospheres and a water-dominated atmosphere. We then simulate the infrared transmission spectra of these atmospheres for JWST instrument modes optimized for transit observation of exoplanet atmospheres: NIRISS, NIRSpec, and MIRI. We then predict the observability of each exoplanet’s atmosphere. TOI-270c and d are excellent targets for detecting atmospheres with JWST transmission spectroscopy, requiring only 1 transit observation with NIRISS, NIRSpec, and MIRI; higher signal-to-noise ratio can be obtained for a clear H-rich atmosphere. Fewer than three transits with NIRISS and NIRSpec may be enough to reveal molecular features. Water-dominated atmospheres require more transits. Water spectral features in water-dominated atmospheres may be detectable with NIRISS in two or three transits. We find that the detection of spectral features in a cloudy, H-rich atmosphere does not require integrations as long as those required for the water-dominated atmosphere, which is consistent with the differences in atmospheric mean molecular weight. TOI-270c and d could be prime targets for JWST transit observations of sub-Neptune atmospheres. These results provide useful predictions for observers who may propose to use JWST to detect and characterize the TOI-270 planet atmospheres.

Sign in / Sign up

Export Citation Format

Share Document