- ID:
- ivo://CDS.VizieR/J/A+A/633/A9
- Title:
- Synthetic photometry as a function of redshift
- Short Name:
- J/A+A/633/A9
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the spectral properties of proto-GCs that would host a supermassive star (SMS). Our main goal is to quantify how such a star would affect the integrated light of the cluster, and to study the detectability of such objects. We computed nonlocal thermal equilibrium atmosphere models for SMS with various combinations of stellar parameters (luminosity, effective temperature, and mass) and metallicities appropriate for GCs, and we predict their emergent spectra. Using these spectra, we calculated the total emission of young proto-GCs with SMS as predicted in a previously reported scenario, and we computed synthetic photometry in UV, optical, and near-IR bands, in particular for the James Webb Space Telescope (JWST). At an effective temperature of 10000K, the spectrum of SMSs shows a Balmer break in emission. This feature is due to strong nonlocal thermal equilibrium effects (implied by the high luminosity) and is not observed in "normal" stars. The hydrogen lines also show a peculiar behavior, with Balmer lines in emission while higher series lines are in absorption. At 7000 K, the Balmer break shows a strong absorption. At high effective temperatures, the Lyman break is found in emission. Cool and luminous SMSs are found to dominate the integrated spectrum of the cluster, except for the UV range. The predicted magnitudes of these proto-GCs are mag_AB_~28-30 between 0.7 and 8um and for redshifts z~4-10, which is detectable with the JWST. The peculiar observational features of cool SMSs imply that they might in principle be detected in color-color diagrams that probe the spectral energy distribution below and above the Balmer break.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/371/1503
- Title:
- Synthetic photometry of RR Lyr
- Short Name:
- J/MNRAS/371/1503
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The luminosities and effective temperatures, as well as the whole bolometric light curves of non-linear convective RR Lyrae models with 0.0001<=Z<=0.006, are transformed into the Sloan Digital Sky Survey (SDSS) photometric system. The obtained ugriz light curves, mean magnitudes and colours, pulsation amplitudes and colour-colour loops are shown and analytical relations connecting pulsational to intrinsic stellar parameters, similar to the ones currently used in the JohnsonCousins filters, are derived. Finally, the behaviour in the colour-colour planes is compared with available observations in the literature and possible systematic uncertainties affecting this comparison are discussed.
- ID:
- ivo://CDS.VizieR/J/MNRAS/504/3730
- Title:
- Synthetic RGB photometry of bright stars
- Short Name:
- J/MNRAS/504/3730
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Although the use of RGB photometry has exploded in the last decades due to the advent of high-quality and inexpensive digital cameras equipped with Bayer-like colour filter systems, there is surprisingly no catalogue of bright stars that can be used for calibration purposes. Since due to their excessive brightness, accurate enough spectrophotometric measurements of bright stars typically cannot be performed with modern large telescopes, we have employed historical 13-colour medium-narrow-band photometric data, gathered with quite reliable photomultipliers, to fit the spectrum of 1346 bright stars using stellar atmosphere models. This not only constitutes a useful compilation of bright spectrophotometric standards well spread in the celestial sphere, the UCM library of spectrophotometric spectra, but allows the generation of a catalogue of reference RGB magnitudes, with typical random uncertainties ~0.01 mag. For that purpose, we have defined a new set of spectral sensitivity curves, computed as the median of 28 sets of empirical sensitivity curves from the literature, that can be used to establish a standard RGB photometric system. Conversions between RGB magnitudes computed with any of these sets of empirical RGB curves and those determined with the new standard photometric system are provided. Even though particular RGB measurements from single cameras are not expected to provide extremely accurate photometric data, the repeatability and multiplicity of observations will allow access to a large amount of exploitable data in many astronomical fields, such as the detailed monitoring of light pollution and its impact on the night sky brightness, or the study of meteors, Solar system bodies, variable stars, and transient objects. In addition, the RGB magnitudes presented here make the sky an accessible and free laboratory for the calibration of the cameras themselves.
- ID:
- ivo://ov-gso/tsap/speconvol
- Title:
- Synthetic Spectra Convolution Service
- Short Name:
- speconvol
- Date:
- 03 Apr 2024 08:16:45
- Publisher:
- OV-GSO Virtual Observatory services
- Description:
- Convolution of normalized synthetic stellar spectra. Up to 3 successive convolutions are allowed on a adjustable portion of a synthetic spectrum, in order to mimic an observable. These convolutions acount for macroturbulence velocity, rotational velocity and instrumental profile. Finally, the output can be Doppler-shifted in order to take into account a stellar radial velocity.
- ID:
- ivo://CDS.VizieR/III/238
- Title:
- Synthetic spectra in the near-IR
- Short Name:
- III/238
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a library of 952 synthetic spectra characterized by -2.5<=[Z/Z_sun_]<=+0.5, 4.5<=logg<=1.0, 3500<=T(eff)<=50000K, at a resolving power (lambda/Delta_lambda) of 20000 over the wavelength range 7650-8750{AA}. The wavelength range covers the near-IR Ca II triplet and the head of the hydrogen's Paschen series, the K I doublet (7664, 7699{AA}), the Na I doublet (8183, 8194{AA}) and the lines of Fe I multiplet N.60 at 8327 and 8388{AA}. The synthetic spectra are based on Kurucz's codes and line data.
- ID:
- ivo://CDS.VizieR/J/ApJ/717/257
- Title:
- Synthetic spectra of dark stars
- Short Name:
- J/ApJ/717/257
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The first stars in the history of the Universe are likely to form in the dense central regions of {sim.to}10^5^-10^6^ M_{sun}_ cold dark matter halos at z{approx}10--50. The annihilation of dark matter particles in these environments may lead to the formation of so-called dark stars, which are predicted to be cooler, larger, more massive and potentially more long-lived than conventional population III stars. Here, we investigate the prospects of detecting high-redshift dark stars with the upcoming James Webb Space Telescope (JWST). We find that all dark stars with masses up to 10^3^ M_{sun}_ are intrinsically too faint to be detected by JWST at z above 6. However, by exploiting foreground galaxy clusters as gravitational telescopes, certain varieties of cool (T_eff_<=30000K) dark stars should be within reach at redshifts up to z{approx}10. If the lifetimes of dark stars are sufficiently long, many such objects may also congregate inside the first galaxies. We demonstrate that this could give rise to peculiar features in the integrated spectra of galaxies at high redshifts, provided that dark stars make up at least {sim.to}1% of the total stellar mass in such objects.
- ID:
- ivo://CDS.VizieR/J/A+A/534/A9
- Title:
- Synthetic spectra of galactic globular clusters
- Short Name:
- J/A+A/534/A9
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We calculated synthetic spectra for typical chemical element mixtures (i.e., a standard alpha-enhanced distribution, and distributions displaying CN and ONa anticorrelations) found in the various subpopulations harboured by individual Galactic globular clusters. From the spectra we determined bolometric corrections to the standard Johnson-Cousins and Stroemgren filters and finally predicted colours. These bolometric corrections and colour-transformations, coupled to our theoretical isochrones with the appropriate chemical composition, provided us with a complete and self-consistent set of theoretical predictions for the effect of abundance variations on the observed cluster colour-magnitude diagrams.
- ID:
- ivo://CDS.VizieR/J/A+A/503/913
- Title:
- Synthetic spectrophotometry for C-rich giants
- Short Name:
- J/A+A/503/913
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Carbon rich objects represent an important phase during the late stages of evolution of low and intermediate mass stars. They contribute significantly to the chemical enrichment and to the infrared light of galaxies. A proper description of their atmospheres is crucial for the determination of fundamental parameters such as effective temperature or mass loss rate. We study the spectroscopic and photometric properties of carbon stars. In the first paper of this series we focus on objects that can be described by hydrostatic models neglecting dynamical phenomena like pulsation and mass loss. As a consequence, the reddening due to circumstellar dust is not included. Our results are collected in a database, which can be used in conjunction with stellar evolution and population synthesis calculations involving the AGB. We have computed a grid of 746 spherically symmetric COMARCS atmospheres covering effective temperatures between 2400 and 4000K, surface gravities from log(g[cm/s^2^])=0.0 to -1.0, metallicities ranging from the solar value down to one tenth of it and C/O ratios in the interval between 1.05 and 5.0. Subsequently, we used these models to create synthetic low resolution spectra and photometric data for a large number of filter systems. The tables including the results are electronically available. First tests of the application on stellar evolution calculations are shown. We have selected some of the most commonly used colours in order to discuss their behaviour as a function of the stellar parameters. A comparison with measured data shows that down to 2800K the agreement between predictions and observations of carbon stars is good and our results may be used to determine quantities like the effective temperature. Below this limit the synthetic colours are much too blue. The obvious reason for these problems is the neglect of circumstellar reddening and structural changes due to pulsation and mass loss.
- ID:
- ivo://CDS.VizieR/J/AJ/127/1227
- Title:
- Synthetic Stroemgren photometry
- Short Name:
- J/AJ/127/1227
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A new grid of theoretical color indices for the Stroemgren uvby photometric system has been derived from MARCS model atmospheres and SSG synthetic spectra for cool dwarf and giant stars having -3.0<=[Fe/H]<=+0.5 and 3000<=T_eff_<=8000K. In the present investigation, we have also analyzed the observed Stroemgren photometry for the classic Population II subdwarfs, compared our "final" (b-y)-Teff relationship with those derived empirically in a number of recent studies and examined in some detail the dependence of the m1 index on [Fe/H].
- ID:
- ivo://CDS.VizieR/J/MNRAS/412/1070
- Title:
- Synthetic supernova extinction curves
- Short Name:
- J/MNRAS/412/1070
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We apply the supernova (SN) extinction curves to reproduce the observed properties of SST J1604+4304 which is a young infrared (IR) galaxy at z~1. The SN extinction curves used in this work were obtained from models of unmixed ejecta of Type II supernovae for the Salpeter initial mass function with a mass range from 8 to 30M_{sun}_ or 8 to 40M_{sun}_. The effect of dust distributions on the attenuation of starlight is investigated by performing the {chi}^2^ fitting method against various dust distributions. These are the commonly used uniform dust screen, the clumpy dust screen and the internal dust geometry. We add to these geometries three scattering properties, namely, no scattering, isotropic scattering and forward-only scattering. Judging from the {chi}^2^ values, we find that the uniform screen models with any scattering property provide good approximations to the real dust geometry.
