- ID:
- ivo://CDS.VizieR/J/AJ/119/1424
- Title:
- Color-temperature relations of M giants
- Short Name:
- J/AJ/119/1424
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- As part of a project to model the integrated spectra and colors of elliptical galaxies through evolutionary synthesis, we have refined our synthetic spectrum calculations of M giants. After critically assessing three effective temperature scales for M giants, we adopted the relation of Dyck et al. for our models. Using empirical spectra of field M giants as a guide, we then calculated MARCS stellar atmosphere models (Gustafsson et al. 1975; Bell et al. 1976) and SSG synthetic spectra (Bell & Gustafsson 1978; Gustafsson & Bell 1979) of these cool stars, adjusting the band absorption oscillator strengths of the TiO bands to better reproduce the observational data. The resulting synthetic spectra are found to be in very good agreement with the K-band spectra of stars of the appropriate spectral type taken from Kleinmann & Hall (1986) as well. Spectral types estimated from the strengths of the TiO bands and the depth of the band head of CO near 2.3 {mu}m quantitatively confirm that the synthetic spectra are good representations of those of field M giants. The broadband colors of the models match the field relations of K and early-M giants very well; for late-M giants, differences between the field star and synthetic colors are probably caused by the omission of spectral lines of VO and H_2_O in the spectrum synthesis calculations. Here, we present four grids of K-band bolometric corrections and colors - Johnson U-V and B-V, Cousins V-R and V-I, Johnson-Glass V-K, J-K, and H-K, and CIT/CTIO V-K, J-K, H-K, and CO - for models having 3000 K {<=} Teff {<=} 4000 K and -0.5 {<=} log(g) {<=} 1.5.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/157/94
- Title:
- Col-OSSOS: Properties of outer solar system objects
- Short Name:
- J/AJ/157/94
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Both physical and dynamical properties must be considered to constrain the origins of the dynamically excited distant solar system populations. We present high-precision (g-r) colors for 25 small (H_r_>5) dynamically excited trans-Neptunian objects (TNOs) and centaurs acquired as part of the Colours of the Outer Solar System Origins Survey. We combine our data set with previously published measurements and consider a set of 229 colors of outer solar system objects on dynamically excited orbits. The overall color distribution is bimodal and can be decomposed into two distinct classes, termed gray and red, that each has a normal color distribution. The two color classes have different inclination distributions: red objects have lower inclinations than the gray ones. This trend holds for all dynamically excited TNO populations. Even in the worst-case scenario, biases in the discovery surveys cannot account for this trend; it is intrinsic to the TNO population. Considering that TNOs are the precursors of centaurs, and that their inclinations are roughly preserved as they become centaurs, our finding solves the conundrum of centaurs being the only outer solar system population identified so far to exhibit this property. The different orbital distributions of the gray and red dynamically excited TNOs provide strong evidence that their colors are due to different formation locations in a disk of planetesimals with a compositional gradient.
- ID:
- ivo://CDS.VizieR/J/MNRAS/446/369
- Title:
- Colour and spectral index from the SLUGGS survey
- Short Name:
- J/MNRAS/446/369
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- As part of the SAGES Legacy Unifying Globulars and GalaxieS (SLUGGS) survey, we stack 1137 Keck DEIMOS (Deep Imaging Multi-Object Spectrograph) spectra of globular clusters from 10 galaxies to study their stellar populations in detail. The stacked spectra have median signal-to-noise ratios of ~90 {AA}^-1^. Besides the calcium triplet, we study weaker sodium, magnesium, titanium and iron lines as well as the H{alpha} and higher order Paschen hydrogen lines. In general, the stacked spectra are consistent with old ages and a Milky Way-like initial mass function. However, we see different metal line index strengths at fixed colour and magnitude, and differences in the calcium triplet-colour relation from galaxy to galaxy. We interpret this as strong evidence for variations in the globular cluster colour-metallicity relation between galaxies. Two possible explanations for the colour-metallicity relation variations are that the average ages of globular clusters vary from galaxy to galaxy or that the average abundances of light elements (i.e. He, C, N and O) differ between galaxies. Stacking spectra by magnitude, we see that the colours become redder and metal line indices stronger with brighter magnitudes. These trends are consistent with the previously reported `blue tilts' being mass-metallicity relations.
- ID:
- ivo://CDS.VizieR/J/AN/333/60
- Title:
- Colour indices of selected OB stars
- Short Name:
- J/AN/333/60
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have applied the method of investigating extinction curves using statistically meaningful samples that was proposed by us 25 years ago. The extensive data sets of the ANS (Astronomical Netherlands Satellite) and 2MASS (Two Micron All Sky Survey) were used, together with UBV photometry to create average extinction curves for samples of OB stars. Our results demonstrate that in the vast majority of cases the extinction curves are very close to the mean galactic extinction curve. Only a few objects were found to be obviously discrepant from the average. The latter phenomenon may be related to nitrogen chemistry in translucent interstellar clouds.
- ID:
- ivo://CDS.VizieR/J/A+AS/102/397
- Title:
- Colour magnitude diagram of M13
- Short Name:
- J/A+AS/102/397
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Two overlapping regions of M13 were observed on April 24, 1989 at the Loiano Observatory with a CDCD camera. A Colour-Magnitude diagram down to the main sequence was derived, as a preliminary search for the blue Horizontal Branch stars in this cluster.
- ID:
- ivo://CDS.VizieR/J/ApJ/582/668
- Title:
- Colours and H{alpha} in galaxy pairs
- Short Name:
- J/ApJ/582/668
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Galaxy-galaxy interactions rearrange the baryons in galaxies and trigger substantial star formation; the aggregate effects of these interactions on the evolutionary histories of galaxies in the universe are poorly understood. We combine B- and R-band photometry and optical spectroscopy to estimate the strengths and timescales of bursts of triggered star formation in the centers of 190 galaxies in pairs and compact groups. Based on an analysis of the measured colors and EW(H{alpha}), we characterize the preexisting and triggered populations separately. The best-fitting burst scenarios assume stronger reddening corrections for line emission than for the continuum and continuous star formation lasting for >~100Myr. The most realistic scenarios require an initial mass function that is deficient in the highest mass stars. The color of the preexisting stellar population is the most significant source of uncertainty. Triggered star formation contributes substantially (probably >~50%) to the R-band flux in the central regions of several galaxies; tidal tails do not necessarily accompany this star formation. Many of the galaxies in our sample have bluer centers than outskirts, suggesting that pre- or nonmerger interactions may lead to evolution along the Hubble sequence. These objects would appear blue and compact at higher redshifts; the older, redder outskirts of the disks would be difficult to detect. Our data indicate that galaxies with larger separations on the sky contain weaker, and probably older, bursts of star formation on average. However, confirmation of these trends requires further constraints on the colors of the older stellar populations and on the reddening for individual galaxies.
- ID:
- ivo://CDS.VizieR/J/MNRAS/357/819
- Title:
- Colours and HI line observations in Virgo
- Short Name:
- J/MNRAS/357/819
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In order to investigate the nature of dwarf low surface brightness (LSB) galaxies we have undertaken a deep B- and I-band CCD survey of a 14-deg^2^ strip in the Virgo Cluster and applied a Fourier convolution technique to explore its dwarf galaxy population down to a central surface brightness of ~26Bmag/arcsec^2^ and a total absolute B magnitude of ~-10. In this paper we carry out an analysis of their morphology, (B-I) colours and atomic hydrogen content.
- ID:
- ivo://CDS.VizieR/J/ApJ/600/L99
- Title:
- Colours of z~6 galaxies in GOODS
- Short Name:
- J/ApJ/600/L99
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report early results on galaxies at z~6 selected from Hubble Space Telescope imaging for the Great Observatories Origins Deep Survey. Spectroscopy of one object with the Advanced Camera for Surveys grism and from the Keck and Very Large Telescope observatories shows a strong continuum break and asymmetric line emission, identified as Ly{alpha} at z=5.83. We find only five spatially extended candidates with signal-to-noise ratios greater than 10, two of which have spectroscopic confirmation. This is much fewer than would be expected if galaxies at z=6 had the same luminosity function as those at z=3. There are many fainter candidates, but we expect substantial contamination from foreground interlopers and spurious detections. Our best estimates favor a z=6 galaxy population with fainter luminosities, higher space density, and similar comoving ultraviolet emissivity to that at z=3, but this depends critically on counts at fluxes fainter than those reliably probed by the current data.
- ID:
- ivo://CDS.VizieR/J/ApJ/702/1472
- Title:
- Column densities for HI, AlIII, SiIV, CIV, OVI
- Short Name:
- J/ApJ/702/1472
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Column densities for HI, AlIII, SiIV, CIV, and OVI toward 109 stars and 30 extragalactic objects have been assembled to study the extensions of these species away from the Galactic plane into the Galactic halo. HI and AlIII mostly trace the warm neutral and warm ionized medium, respectively, while SiIV, CIV, and OVI trace a combination of warm photoionized and collisionally ionized plasmas. The much larger object sample compared to previous studies allows us to consider and correct for the effects of the sample bias that has affected earlier but smaller surveys of the gas distributions. The observations are compared to the predictions of the various models for the production of the transition temperature gas in the halo.
- ID:
- ivo://CDS.VizieR/J/ApJ/894/142
- Title:
- Column densities from HST/COS SiIV AGN sight lines
- Short Name:
- J/ApJ/894/142
- Date:
- 19 Jan 2022 13:10:08
- Publisher:
- CDS
- Description:
- We develop a kinematical model for the Milky Way SiIV-bearing gas to determine its density distribution and kinematics. This model is constrained by a column density line-shape sample extracted from the Hubble Space Telescope/Cosmic Origins Spectrograph archival data, which contains 186 active galactic nucleus sight lines. We find that the SiIV ion density distribution is dominated by an extended disk along the z-direction (above or below the midplane), i.e., n(z)=n_0_exp(-(z/z_0_)^0.82^), where z_0_ is the scale height of 6.3_-1.5_^+1.6^kpc (northern hemisphere) and 3.6_-0.9_^+1.0^kpc (southern hemisphere). The density distribution of the disk in the radial direction shows a sharp edge at 15-20kpc given by, n(r_XY_)=n_0_exp(-(r_XY_/r_0_)^3.36^), where r_0_~12.5+/-0.6kpc. The difference of density distributions over r_XY_ and z directions indicates that the warm gas traced by SiIV is mainly associated with disk processes (e.g., feedback or cycling gas) rather than accretion. We estimate the mass of the warm gas (within 50kpc) is log(M(50kpc)/M_{sun}_)~8.1 (assuming Z~0.5Z_{sun}_), and a 3{sigma} upper limit of log(M(250kpc)/M_{sun}_)~9.1 (excluding the Magellanic system). Kinematically, the warm gas disk is nearly co-rotating with the stellar disk at v_rot_=215+/-3km/s, which lags the midplane rotation by about 8km/s/kpc (within 5kpc). Meanwhile, we note that the warm gas in the northern hemisphere has significant accretion with vacc of 69+/-7km/s at 10kpc (an accretion rate of -0.60_-0.13_^+0.11^M_{sun}_/yr), while in the southern hemisphere, there is no measurable accretion, with an upper limit of 0.4M_{sun}_/yr.