- ID:
- ivo://CDS.VizieR/J/ApJ/860/41
- Title:
- Spectral & environment properties of z~2 QSO pairs
- Short Name:
- J/ApJ/860/41
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first results from our survey of intervening and proximate Lyman limit systems (LLSs) at z~2.0-2.5 using the Wide Field Camera 3 on board the Hubble Space Telescope. The quasars in our sample are projected pairs with proper transverse separations R_{perp}_<=150kpc and line-of- sight velocity separations <~11000km/s. We construct a stacked ultraviolet (rest-frame wavelengths 700-2000{AA}) spectrum of pairs corrected for the intervening Lyman forest and Lyman continuum absorption. The observed spectral composite presents a moderate flux excess for the most prominent broad emission lines, a ~30% decrease in flux at {lambda}=800-900{AA} compared to a stack of brighter quasars not in pairs at similar redshifts, and lower values of the mean free path of the HI ionizing radiation for pairs ({lambda}_mfp_^912^=140.7+/-20.2h_70_^-1^Mpc) compared to single quasars ({lambda}_mfp_^912^=213.8+/-28h_70_^-1^Mpc) at the average redshift z~2.44. From the modeling of LLS absorption in these pairs, we find a higher (~20%) incidence of proximate LLSs with logN_HI_>=17.2 at {delta}v<5000km/s compared to single quasars (~6%). These two rates are different at the 5{sigma} level. Moreover, we find that optically thick absorbers are equally shared between foreground and background quasars. Based on these pieces of evidence, we conclude that there is a moderate excess of gas-absorbing Lyman continuum photons in our closely projected quasar pairs compared to single quasars. We argue that this gas arises mostly within large-scale structures or partially neutral regions inside the dark matter halos where these close pairs reside.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJS/228/16
- Title:
- Spectra of a Holmium in the near-UV. I. Ho I.
- Short Name:
- J/ApJS/228/16
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Fourier Transform spectra of a Holmium hollow cathode discharge lamp have been investigated in the UV spectral range from 25000 up to 31530cm^-1^ (317 to 400nm). Two Ho spectra have been measured with neon and argon as buffer gases. Based on the intensity ratios from these two spectra, a distinction was made between atomic and ionic lines (ionic lines are discussed in an accompanying paper). Using the known Ho I energy levels, 71 lines could be classified as transitions of atomic Ho, 34 of which have not been published previously. Another 32 lines, which could not be classified, are listed in the literature and assigned as atomic Ho. An additional 370 spectral lines have been assigned to atomic Ho based on the signal-to-noise ratio in the two spectra measured under different discharge conditions, namely with buffer gases argon and neon, respectively. These 370 lines have not been previously listed in the literature.
- ID:
- ivo://CDS.VizieR/J/ApJS/228/17
- Title:
- Spectra of a Holmium in the near-UV. II.
- Short Name:
- J/ApJS/228/17
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Fourier Transform spectra of Holmium (Ho) in the UV spectral range from 31530 to 25000cm^-1^ (317 to 400nm) have been investigated, particularly focusing on the ionic lines. The distinction between the different degrees of ionization (I, II, and III) is based on differences in signal-to-noise ratios from two Ho spectra, which have been measured with different buffer gases, i.e., neon and argon. Based on 106 known Ho II and 126 known Ho III energy levels, 97 lines could be classified as transitions of singly ionized Ho and 9 lines could be classified as transitions of doubly ionized Ho. Of the 97 Ho II lines, 6 have not been listed in the extant literature. Another 215 lines have been assigned to Ho II, though they could not be classified on the basis of the known energy levels.
- ID:
- ivo://CDS.VizieR/J/A+A/659/A35
- Title:
- Spectra of IRAS 17449+2320
- Short Name:
- J/A+A/659/A35
- Date:
- 04 Mar 2022 00:58:00
- Publisher:
- CDS
- Description:
- We report the first detection of the magnetic field in a star of FS CMa type, a subgroup of objects characterized by the B[e] phenomenon. The split of magnetically sensitive lines in IRAS 17449+2320 determines the magnetic field modulus of 6.2+/-0.2kG. Spectral lines and their variability reveal the presence of a B-type spectrum and a hot continuum source in the visible. The hot source confirms GALEX UV photometry. Because there is a lack of spectral lines for the hot source in the visible, the spectral fitting gives only the lower temperature limit of the hot source, which is 50000K, and the upper limit for the B-type star of 11100K. The V/R ratio of the Halpha line shows quasiperiodic behavior on timescale of 800 days. We detected a strong red-shifted absorption in the wings of Balmer and OI lines in some of the spectra. The absorption lines of helium and other metals show no, or very small, variations, indicating unusually stable photospheric regions for FS CMa stars. We detected two events of material infall, which were revealed to be discrete absorption components of resonance lines. The discovery of the strong magnetic field together with the Gaia measurements of the proper motion show that the most probable nature of this star is that of a post-merger object created after the leaving the binary of the birth cluster. Another possible scenario is a magnetic Ap star around Terminal-Age Main Sequence (TAMS). On the other hand, the strong magnetic field defies the hypothesis that IRAS 17449+2320 is an extreme classical Be star. Thus, IRAS 17449+2320 provides a pretext for exploring a new explanation of the nature of FS CMa stars or, at least, a group of stars with very similar spectral properties.
- ID:
- ivo://CDS.VizieR/J/A+A/391/641
- Title:
- Spectroscopic study of sigma Geminorum from IUE
- Short Name:
- J/A+A/391/641
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The IUE spectra of {sigma} Gem have been taken from the NASA IUE archive using IDL (Interactive Data Language). The spectra have been observed in 1979-1986 period. All the spectra analysed in the present study have NEWSIPS reductions and consist of 25 LWP, 8 LWR and 5 SWP images in high resolution, and 2 LWP and 14 SWP images in low dispersion. The emission lines, identified as activity indicators and originating in the chromosphere and transition region, are seen in the spectra. The emission line fluxes and equivalent widths are computed based on Gaussian profile fitting procedures to examine the existence of any line flux variation that depends on time or orbital phase. It was found that there is a flux variation with time and orbital phase that is in good agreement with the photometric light curve variation. By comparing the flux variation with simultaneous light curve variation, it can be shown that there is a relation between the ultraviolet flux variation and the spot activity of the system, as shown by Ayres et al. (1984ApJ...279..197A) and Engvold et al. (1988A&A...192..234E) based on their IUE (with IUESIPS reduction) spectral analysis. Moreover, it was inferred that there is no ultraviolet excess in {sigma} Gem by comparing the spectra of {beta} Gem taken as a comparison star. The Mg II h and k radial velocity curves of {sigma} Gem were in a good agreement with data obtained by Eker (1986MNRAS.221..947E) and Duemmler et al. (1997A&AS..123..209D).
- ID:
- ivo://CDS.VizieR/J/MNRAS/395/855
- Title:
- Spectroscopy (310-1040nm) of HH 202
- Short Name:
- J/MNRAS/395/855
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results of deep echelle spectrophotometry of the brightest knot of the Herbig-Haro object HH 202 in the Orion Nebula - HH 202-S - using the Ultraviolet Visual Echelle Spectrograph in the spectral range from 3100 to 10400{AA} The high spectral resolution of the observations has permitted to separate the component associated with the ambient gas from that associated with the gas flow. We derive electron densities and temperatures from different diagnostics for both components, as well as the chemical abundances of several ions and elements from collisionally excited lines, including the first determinations of Ca^+^ and Cr^+^ abundances in the Orion Nebula. We also calculate the He+, C^2+^, O+ and O^2+^ abundances from recombination lines.
- ID:
- ivo://CDS.VizieR/J/ApJS/213/28
- Title:
- Spectrum analysis of CrII
- Short Name:
- J/ApJS/213/28
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have made new observations of the spectrum of singly ionized chromium (CrII) in the region 2850-37900{AA} with the National Institute of Standards and Technology 2m Fourier transform spectrometer. These data extend our previously reported observations in the near-ultra-violet region. We present a comprehensive list of more than 5300 CrII lines classified as transitions among 456 even and 457 odd levels, 179 of which are newly located in this work. Using highly excited levels of the 3d^4^(^5^D)5g, 3d^4^(^5^D)6g, and 3d^4^(^5^D)6h configurations, we derive an improved ionization energy of 132971.02+/-0.12cm^-1^ (16.486305+/-0.000015eV).
- ID:
- ivo://CDS.VizieR/J/MNRAS/361/1102
- Title:
- Spectrum of {epsilon} Eri
- Short Name:
- J/MNRAS/361/1102
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Measurements of ultraviolet line fluxes from Space Telescope Imaging Spectrograph and Far-Ultraviolet Spectroscopic Explorer spectra of the K2-dwarf eps Eri are reported. These are used to develop new emission measure distributions and semi-empirical atmospheric models for the chromosphere and lower transition region of the star. These models are the most detailed constructed to date for a main-sequence star other than the Sun. New ionization balance calculations, which account for the effect of finite density on dielectronic recombination rates, are presented for carbon, nitrogen, oxygen and silicon. The results of these calculations are significantly different from the standard Arnaud & Rothenflug ion balance, particularly for alkali-like ions. The new atmospheric models are used to place constraints on possible first ionization potential (FIP)-related abundance variations in the lower atmosphere and to discuss limitations of single-component models for the interpretation of certain optically thick line fluxes.
379. Spectrum of KQ Pup
- ID:
- ivo://CDS.VizieR/J/A+A/258/423
- Title:
- Spectrum of KQ Pup
- Short Name:
- J/A+A/258/423
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- (no description available)
- ID:
- ivo://CDS.VizieR/J/ApJS/187/149
- Title:
- StarCAT: STIS UV echelle spectra of stars
- Short Name:
- J/ApJS/187/149
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- StarCAT is a catalog of high resolution ultraviolet spectra of objects classified as "stars," recorded by Space Telescope Imaging Spectrograph (STIS) during its initial seven years of operations (1997-2004). StarCAT is based on 3184 echelle observations of 545 distinct targets, with a total exposure duration of 5.2Ms. For many of the objects, broad ultraviolet coverage has been achieved by splicing echellegrams taken in two or more FUV (1150-1700{AA}) and/or NUV (1600-3100{AA}) settings. In cases of multiple pointings on conspicuously variable sources, spectra were separated into independent epochs. Otherwise, different epochs were combined to enhance the signal-to-noise ratio (S/N). A post-facto correction to the "calstis" pipeline data sets compensated for subtle wavelength distortions identified in a previous study of the STIS calibration lamps. An internal "fluxing" procedure yielded coherent spectral energy distributions (SEDs) for objects with broadly overlapping wavelength coverage. The best StarCAT material achieves 300m/s internal velocity precision; absolute accuracy at the 1km/s level; photometric accuracy of order 4%; and relative flux precision several times better (limited mainly by knowledge of SEDs of UV standard stars). While StarCAT represents a milestone in the large-scale post-processing of STIS echellegrams, a number of potential improvements in the underlying "final" pipeline are identified.
