Search

Start Over Subject ultraviolet astronomy
201. HST/STIS spectra of alpha Cen A
ID:
ivo://CDS.VizieR/J/A+A/415/331
Title:
HST/STIS spectra of alpha Cen A
Short Name:
J/A+A/415/331
Date:
21 Oct 2021
Publisher:
CDS
Description:
This table is part of a paper is which a study of the alpha Cen A spectrum recorded with the E140 grating by HST/STIS between 1140 and 1670{AA} is presented. In this spectrum the authors have identified a total of 662 emission features of which 77 are due to blends of two or more lines, 71 are due to unidentified transitions, and 514 are identified as due to single emission lines.
202. HST survey for Lyman limit systems. I.
ID:
ivo://CDS.VizieR/J/ApJS/195/16
Title:
HST survey for Lyman limit systems. I.
Short Name:
J/ApJS/195/16
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a set of 71 quasars observed in the near ultraviolet with the PR200L prism on the Advanced Camera for Surveys and the G280 grism on the Wide Field Camera 3 (WFC3) on board the Hubble Space Telescope. The quasars were selected from the Sloan Digital Sky Survey data to search for intervening Lyman limit system (LLS) absorption. The sample was subjected to the constraints that the quasars have AB magnitude g'<18.5, quasar emission redshift 2.3<z_em_<2.6, and lack strong BAL or z~z_em_ absorption. The median emission redshift of the sample is {bar}z=2.403. The data were all processed using custom data reduction pipelines, and the one-dimensional spectra have sufficient signal-to-noise ratio and resolution to easily identify absorption from LLS over the redshift range 1.2<z<2.5. The WFC3 data presented here are the first non-calibration spectra from the G280 grism.
203. HST survey for Lyman limit systems. II.
ID:
ivo://CDS.VizieR/J/ApJ/765/137
Title:
HST survey for Lyman limit systems. II.
Short Name:
J/ApJ/765/137
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the first science results from our Hubble Space Telescope survey for Lyman limit absorption systems (LLS) using the low dispersion spectroscopic modes of the Advanced Camera for Surveys and the Wide Field Camera 3. Through an analysis of 71 quasars, we determine the incidence frequency of LLS per unit redshift and per unit path length, l(z) and l(X), respectively, over the redshift range 1<z<2.6, and find a weighted mean of l(X)=0.29+/-0.05 for 2.0<z<2.5 through a joint analysis of our sample and that of Ribaudo et al. (2011, J/ApJ/736/42). Through stacked spectrum analysis, we determine a median (mean) value of the mean free path to ionizing radiation at z=2.4 of {lambda}^912^_mfp_=243(252)h^-1^_72_Mpc, with an error on the mean value of +/-43h^-1^_72_Mpc. We also re-evaluate the estimates of {lambda}^912^_mfp_ from Prochaska et al. (2010, J/ApJ/718/392) and place constraints on the evolution of {lambda}^912^_mfp_ with redshift, including an estimate of the "breakthrough" redshift of z=1.6. Consistent with results at higher z, we find that a significant fraction of the opacity for absorption of ionizing photons comes from systems with N_HI_<=10^17.5^cm^-2^ with a value for the total Lyman opacity of {tau}^Lyman^_eff_=0.40+/-0.15. Finally, we determine that at minimum, a 5-parameter (4 power law) model is needed to describe the column density distribution function f(N_HI_,X) at z~2.4, find that f(N_HI_,X) undergoes no significant change in shape between z~2.4 and z~3.7, and provide our best fit model for f(N_HI_,X).
204. HST Ultraviolet Atlas of Nearby Galaxies
ID:
ivo://mast.stsci/siap/hst.maoz_atlas
Title:
HST Ultraviolet Atlas of Nearby Galaxies
Short Name:
HST.maoz_atlas
Date:
23 Jul 2020 19:27:41
Publisher:
Space Telescope Science Institute Archive
Description:
A pictorial atlas of UV (2300 Å) images, obtained with the Hubble Space Telescope (HST) Faint Object Camera, of the central 22''× 22'' of 110 galaxies (Maoz, Filippenko, Ho, Macchetto, Rix, & Schneider 1996). The observed galaxies are an unbiased selection constituting about one half of a complete sample of all large (D>6 arcmin) and nearby (V< 2000 km/s ) galaxies. This is the first extensive UV imaging survey of normal galaxies. The data are useful for studying star formation, low-level nuclear activity, and UV emission by evolved stellar populations in galaxies. At the HST resolution (~ 0.05''), the images display an assortment of morphologies and UV brightnesses. These include bright nuclear point sources, compact young star clusters scattered in the field or arranged in circumnuclear rings, centrally-peaked diffuse light distributions, and galaxies with weak or undetected UV emission. We measure the integrated ~2300 Å flux in each image, and classify the UV morphology.
205. HST UV-IR photometry in CLASH galaxy clusters
ID:
ivo://CDS.VizieR/J/ApJ/848/37
Title:
HST UV-IR photometry in CLASH galaxy clusters
Short Name:
J/ApJ/848/37
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a new method for photometering objects in galaxy clusters. We introduce a mode-filtering technique for removing spatially variable backgrounds, improving both detection and photometric accuracy (roughly halving the scatter in the red sequence compared to previous catalogs of the same clusters). This method is based on robustly determining the distribution of background pixel values and should provide comparable improvement in photometric analysis of any crowded fields. We produce new multiwavelength catalogs for the 25 CLASH cluster fields in all 16 bandpasses from the UV through the near-IR, as well as rest-frame magnitudes. A comparison with spectroscopic values from the literature finds a ~30% decrease in the redshift deviation from previously released CLASH photometry. This improvement in redshift precision, in combination with a detection scheme designed to maximize purity, yields a substantial upgrade in cluster member identification over the previous CLASH galaxy catalog. We construct luminosity functions for each cluster, reliably reaching depths of at least 4.5mag below M* in every case, and deeper still in several clusters. We measure M* , {alpha}, and their redshift evolution, assuming the cluster populations are coeval, and find little to no evolution of {alpha}{<~}-0.9<~{alpha}{<~}-0.8, and M* values consistent with passive evolution. We present a catalog of galaxy photometry, photometric and spectroscopic redshifts, and rest-frame photometry for the full fields of view of all 25 CLASH clusters. Not only will our new photometric catalogs enable new studies of the properties of CLASH clusters, but mode-filtering techniques, such as those presented here, should greatly enhance the data quality of future photometric surveys of crowded fields.
206. Hubble Infrared Pure Parallel Imaging Extragalactic Survey (HIPPIES)
ID:
ivo://mast.stsci/hippies
Title:
Hubble Infrared Pure Parallel Imaging Extragalactic Survey (HIPPIES)
Short Name:
HST.HIPPIES
Date:
22 Jul 2020 22:31:09
Publisher:
Space Telescope Science Institute Archive
Description:
Hubble Infrared Pure Parallel Imaging Extragalactic Survey (HIPPIES) utilizes long-duration pure parallel visits (~> 3 orbits) of HST at high Galactic latitude (|b|>20o) to take deep, multi-band images in WFC3 (since Cycle 17) and in ACS (starting Cycle 18). It is unique in its large number of descrete fields along random sightlines, and thus is complementary to other surveys over contiguous fields but along limited sightlines.
207. Hubble Space Telescope Ultraviolet Images of the UDF and HDF
ID:
ivo://mast.stsci/siap/udfuv
Title:
Hubble Space Telescope Ultraviolet Images of the UDF and HDF
Short Name:
HST.udfuv
Date:
22 Jul 2020 22:22:46
Publisher:
Space Telescope Science Institute Archive
Description:
Wavelength coverage of the Hubble Ultra Deep Field (UDF) has been extended to ultraviolet wavelength observations. Observations include ACS-SBC images in the Far-UV {1500 Angstrom} and WFPC2 images in the Near-UV {F300W} during excution of the HST Treasury program 10403 ( PI Harry Teplitz -- California Institute of Technology). Included with this set of data are ACS/SBC observations of the Hubble Deep Field (HDF) North.
208. Hubble spectroscopy of LB-1 (LS V +22 25)
ID:
ivo://CDS.VizieR/J/A+A/649/A167
Title:
Hubble spectroscopy of LB-1 (LS V +22 25)
Short Name:
J/A+A/649/A167
Date:
22 Feb 2022
Publisher:
CDS
Description:
LB-1 has variously been proposed as either an X-ray dim B-type star plus black hole (B+BH) binary, or a Be star plus an inflated stripped star (Be+Bstr) binary. The Space Telescope Imaging Spectrograph (STIS) on board HST was used to obtain a flux-calibrated spectrum that is compared with non-LTE spectral energy distributions (SED) and line profiles for the proposed models. The Hubble data, together with the Gaia EDR3 parallax, provide tight constraints on the properties and stellar luminosities of the system. In the case of the Be+Bstr model we adopt the published flux ratio for the Be and Bstr stars, re-determine the Teff of the Bstr using the silicon ionization balance, and infer Teff for the Be star from the fit to the SED. We derive stellar parameters consistent with previous results, but with greater precision enabled by the Hubble SED. While the Be+Bstr model is a better fit to the HeI lines and cores of the Balmer lines in the optical, the B+BH model provides a better fit to the SiIV resonance lines in the UV. The analysis also implies that the Bstr star has roughly twice solar silicon abundance, which is difficult to reconcile with a stripped star origin. The Be star on the other hand has a rather low luminosity, and a spectroscopic mass inconsistent with its possible dynamical mass. The fit to the UV can be significantly improved by reducing the Teff and radius of the Be star, though at the expense of leading to a different mass ratio. In the B+BH model, the single B-type spectrum is a good match to the UV spectrum. Adopting a mass ratio of 5.1+/-0.1 (Liu et al., 2020ApJ...900...42L) implies a BH mass of 21^+9^_-8_ solar masses.
209. Hydrogen volume densities in nearby galaxies
ID:
ivo://CDS.VizieR/J/MNRAS/428/3355
Title:
Hydrogen volume densities in nearby galaxies
Short Name:
J/MNRAS/428/3355
Date:
21 Oct 2021
Publisher:
CDS
Description:
Using a simple model of photodissociated atomic hydrogen on a galactic scale, it is possible to derive total hydrogen volume densities. These densities, obtained through a combination of atomic hydrogen, far-ultraviolet and metallicity data, provide an independent probe of the combined atomic and molecular hydrogen gas in galactic discs. We present a new, flexible and fully automated procedure using this simple model. This automated method will allow us to take full advantage of a host of available data on galaxies in order to calculate the total hydrogen volume densities of the giant molecular clouds surrounding sites of recent star formation. Until now this was only possible on a galaxy-by-galaxy basis using by-eye analysis of candidate photodissociation regions. We test the automated method by adopting various models for the dust-to-gas ratio and comparing the resulting densities for M74, including a new metallicity map of M74 produced by integral field spectroscopy. We test the procedure against previously published M83 volume densities based on the same method and find no significant differences. The range of total hydrogen volume densities obtained for M74 is approximately 5-700cm^-3^. Different dust-to-gas ratio models do not result in measurably different densities. The cloud densities presented here mean that M74 is added to the list of galaxies analysed using the assumption of photodissociated atomic hydrogen occurring near sites of recent star formation, and consolidate the method. For the first time, full metallicity maps are included in the analysis as opposed to metallicity gradients. The results will need to be compared with other tracers of the interstellar medium and photodissociation regions, such as CO and CII, in order to test our basic assumptions, specifically our assumption that the HI we detect originates in photodissociation regions.
210. IGM absorbers toward HE 0226-4110
ID:
ivo://CDS.VizieR/J/ApJS/164/1
Title:
IGM absorbers toward HE 0226-4110
Short Name:
J/ApJS/164/1
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present an analysis of the FUSE (Far Ultraviolet Spectroscopic Explorer) and HST (Hubble Space Telescope) STIS E140M spectra of HE 0226-4110 (z=0.495). We detect 56 Lyman absorbers and five OVI absorbers.