Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userAll NIRspec needs is HST/WFC3 pre-imaging? The use of Milky Way Stars in WFC3 Imaging to Register NIRspec MSA Observations
146
0
0.0
(
0
)
Authors
B.W. Holwerda
Ask ChatGPT about the research
No Arabic abstract
The James Webb Space Telescope (JWST) will be an exquisite new near-infrared observatory with imaging and multi-object spectroscopy through ESAs NIRspec instrument with its unique Micro-Shutter Array (MSA), allowing for slits to be positioned on astronomical targets by opening specific 0.002-wide micro shutter doors. To ensure proper target acquisition, 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 Target Acquisition (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 $zsim8$ 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 TAs are $m_{lim}>24.5$ AB in WFC3 F125W, (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 $sim23$ AB mag in WFC3 F125W, (d) no specific Galactic latitude requires deeper TA imaging due to a lack of Galactic stars, and (e) a depth of $sim24$ AB mag in WFC3 F125W is needed if a guide star in the same MSA quadrant as a target is required. We take the example of a BoRG identified $zsim8$ candidate galaxy and require a Galactic star within 20 of it. In this case, a depth of 25.5 AB in F125W is required (with $sim$97% confidence).
rate research
Read More
We present Wide Field Camera 3 images taken with the Hubble Space Telescope within a single field in the southern grand design star-forming galaxy M83. Based on their size, morphology and photometry in continuum-subtracted H$alpha$, [SII], H$beta$, [OIII] and [OII] filters, we have identified 60 supernova remnant candidates, as well as a handful of young ejecta-dominated candidates. A catalog of these remnants, their sizes and, where possible their H$alpha$ fluxes are given. Radiative ages and pre-shock densities are derived from those SNR which have good photometry. The ages lie in the range $2.62 < log(tau_{rm rad}/{rm yr}) < 5.0$, and the pre-shock densities at the blast wave range over $0.56 < n_0/{rm cm^{-3}} < 1680$. Two populations of SNR have been discovered. These divide into a nuclear and spiral arm group and an inter-arm population. We infer an arm to inter-arm density contrast of 4. The surface flux in diffuse X-rays is correlated with the inferred pre-shock density, indicating that the warm interstellar medium is pressurised by the hot X-ray plasma. We also find that the interstellar medium in the nuclear region of M83 is characterized by a very high porosity and pressure and infer a SNR rate of one per 70-150 yr for the nuclear ($R<300 $pc) region. On the basis of the number of SNR detected and their radiative ages, we infer that the lower mass of Type II SNe in M83 is $M_{rm min} = 16^{+7}_ {-5}$ M$_{odot}$. Finally we give evidence for the likely detection of the remnant of the historical supernova, SN1968L.
The planetary nebula (PN) NGC 5189 around a Wolf-Rayet [WO] central star demonstrates one of the most remarkable complex morphologies among PNe with many multi-scale structures, showing evidence of multiple outbursts from an AGB progenitor. In this study we use multi-wavelength Hubble Space Telescope Wide Field Camera 3 (WFC3) observations to study the morphology of the inner 0.3 pc $times$ 0.2 pc region surrounding the central binary that appears to be a relic of a more recent outburst of the progenitor AGB star. We applied diagnostic diagrams based on emission line ratios of H$alpha$ $lambda$6563, [O III] $lambda$5007, and [S II] $lambdalambda$6717,6731 images to identify the location and morphology of low-ionization structures within the inner nebula. We distinguished two inner, low-ionization envelopes from the ionized gas, within a radius of 55 arcsec ($sim$ 0.15 pc) extending from the central star: a large envelope expanding toward the northeast, and its smaller counterpart envelope in the opposite direction toward the southwest of the nebula. These low-ionization envelopes are surrounded by a highly-ionized gaseous environment. We believe that these low-ionization expanding envelopes are a result of a powerful outburst from the post-AGB star that created shocked wind regions as they propagate through the previously expelled material along a symmetric axis. Our diagnostic mapping using high-angular resolution line emission imaging can provide a novel approach to detection of low-ionization regions in other PNe, especially those showing a complex multi-scale morphology.
We present the results of a comprehensive, near-UV-to-near-IR Hubble Space Telescope WFC3 imaging study of the young planetary nebula (PN) NGC 6302, the archetype of the class of extreme bi-lobed, pinched-waist PNe that are rich in dust and molecular gas. The new WFC3 emission-line image suite clearly defines the dusty toroidal equatorial structure that bisects NGC 6302s polar lobes, and the fine structures (clumps, knots, and filaments) within the lobes. The most striking aspect of the new WFC3 image suite is the bright, S-shaped 1.64 micron [Fe II] emission that traces the southern interior of the east lobe rim and the northern interior of the west lobe rim, in point-symmetric fashion. We interpret this [Fe II] emitting region as a zone of shocks caused by ongoing, fast (~100 km/s), collimated, off-axis winds from NGC 6302s central star(s). The [Fe II] emission and a zone of dusty, N- and S-rich clumps near the nebular symmetry axis form wedge-shaped structures on opposite sides of the core, with boundaries marked by sharp azimuthal ionization gradients. Comparison of our new images with earlier HST/WFC3 imaging reveals that the object previously identified as NGC 6302s central star is a foreground field star. Shell-like inner lobe features may instead pinpoint the obscured central stars actual position within the nebulas dusty central torus. The juxtaposition of structures revealed in this HST/WFC3 imaging study of NGC 6302 presents a daunting challenge for models of the origin and evolution of bipolar PNe.
We present a tally of Milky Way late-type dwarf stars in 68 WFC3 pure-parallel fields (227 arcmin^2) from the Brightest of Reionizing Galaxies (BoRG) survey for high-redshift galaxies. Using spectroscopically identified M-dwarfs in two public surveys, the CANDELS and the ERS mosaics, we identify a morphological selection criterion using the half-light radius (r50), a near-infrared J-H, G-J color region where M-dwarfs are found, and a V-J relation with M-dwarf subtype. We apply this morphological selection of stellar objects, color-color selection of M-dwarfs and optical-near-infrared color subtyping to compile a catalog of 274 M-dwarfs belonging to the disk of the Milky Way with a limiting magnitude of m_F125W < 24. Based on the M-dwarfs statistics, we conclude that (a) the previously identified North/South discrepancy in M-dwarf numbers persists in our sample; there are more M-dwarfs in the Northern fields on average than in Southern ones, (b) the Milky Ways single disk scale-height for M-dwarfs is 0.3-4 kpc, depending on sub-type, (c) {bf ERRATUM:} we present corrected coordinates (AstroPy) and distances and find a constant $z_0$=600 pc for all types. (d) a second component is visible in the vertical distribution, with a different, much higher scale-height. We report the M-dwarf component of the Sagittarius stream in one of our fields with 11 confirmed M-dwarfs, 7 of which are at the streams distance. The dwarf scale-height and the relative low incidence in our fields of L- and T-dwarfs in these fields makes it unlikely that these stars will be interlopers in great numbers in color-selected samples of high-redshift galaxies. The relative ubiquity of M-dwarfs however will make them ideal tracers of Galactic Halo substructure with EUCLID and reference stars for JWST observations.
We report on deep near-infrared observations obtained with the Wide Field Camera 3 (WFC3) onboard the Hubble Space Telescope (HST) of the first five confirmed gravitational lensing events discovered by the Herschel Astrophysical Terahertz Large Area Survey (H-ATLAS). We succeed in disentangling the background galaxy from the lens to gain separate photometry of the two components. The HST data allow us to significantly improve on previous constraints of the mass in stars of the lensed galaxy and to perform accurate lens modelling of these systems, as described in the accompanying paper by Dye et al. We fit the spectral energy distributions of the background sources from near-IR to millimetre wavelengths and use the magnification factors estimated by Dye et al. to derive the intrinsic properties of the lensed galaxies. We find these galaxies to have star-formation rates of approximately 400 to 2000 M_sol/yr, with approximately (6-25)x10^10 M_sol of their baryonic mass already turned into stars. At these rates of star formation, all remaining molecular gas will be exhausted in less than 100 Myr, reaching a final mass in stars of a few 10^11 M_sol. These galaxies are thus proto-ellipticals caught during their major episode of star formation, and observed at the peak epoch z=1.5-3 of the cosmic star formation history of the Universe.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
