W. Seifert

BLACK HOLE MASS ESTIMATES BASED ON C IV ARE CONSISTENT WITH THOSE BASED ON THE BALMER LINES

Using a sample of high-redshift lensed quasars from the CASTLES project with observed-frame ultraviolet or optical and near-infrared spectra, we have searched for possible biases between supermassive black hole (BH) mass estimates based on the C IV, Hα, and Hβ broad emission lines. Our sample is based upon that of Greene, Peng, & Ludwig, expanded with new near-IR spectroscopic observations, consistently analyzed high signal-to-noise ratio (S/N) optical spectra, and consistent continuum luminosity estimates at 5100 A. We find that BH mass estimates based on the full width at half-maximum (FWHM) of C IV show a systematic offset with respect to those obtained from the line dispersion, σ_l , of the same emission line, but not with those obtained from the FWHM of Hα and Hβ. The magnitude of the offset depends on the treatment of the He II and Fe II emission blended with C IV, but there is little scatter for any fixed measurement prescription. While we otherwise find no systematic offsets between C IV and Balmer line mass estimates, we do find that the residuals between them are strongly correlated with the ratio of the UV and optical continuum luminosities. This means that much of the dispersion in previous comparisons of C IV and Hβ BH mass estimates are due to the continuum luminosities rather than to any properties of the lines. Removing this dependency reduces the scatter between the UV- and optical-based BH mass estimates by a factor of approximately two, from roughly 0.35 to 0.18 dex. The dispersion is smallest when comparing the C IV σ l mass estimate, after removing the offset from the FWHM estimates, and either Balmer line mass estimate. The correlation with the continuum slope is likely due to a combination of reddening, host contamination, and object-dependent SED shapes. When we add additional heterogeneous measurements from the literature, the results are unchanged. Moreover, in a trial observation of a remaining outlier, the origin of the deviation is clearly due to unrecognized absorption in a low S/N spectrum. This not only highlights the importance of the quality of the observations, but also raises the question whether cases like this one are common in the literature, further biasing comparisons between C IV and other broad emission lines.

LBT/LUCIFER observations of the z ~ 2 lensed galaxy J0900+2234

We present rest-frame optical images and spectra of the gravitationally lensed, star-forming galaxy J0900+2234 (z = 2.03). The observations were performed with the newly commissioned LUCIFER1 near-infrared (NIR) instrument mounted on the Large Binocular Telescope. We fitted lens models to the rest-frame optical images and found that the galaxy has an intrinsic effective radius of 7.4 ± 0.8 kpc with a lens magnification factor of about 5 for the A and B components. We also discovered a new arc belonging to another lensed high-z source galaxy, which makes this lens system a potential double Einstein ring system. Using the high signal-to-noise ratio rest-frame spectra covered by the H + K band, we detected Hβ, [Oxa0III], Hα, [Nxa0II], and [Sxa0II] emission lines. Detailed physical properties of this high-z galaxy were derived. The extinction toward the ionized Hxa0II regions (Eg (B – V)) was computed from the flux ratio of Hα and Hβ and appears to be much higher than that toward the stellar continuum (Es (B – V)), derived from the optical and NIR broadband photometry fitting. The metallicity was estimated using N2 and O3N2 indices. It is in the range of solar abundance, which is much lower than for typical z ~ 2 star-forming galaxies. From the flux ratio of [Sxa0II]λ6717 and [Sxa0II]λ6732, we found that the electron number density of the Hxa0II regions in the high-z galaxy was 1000 cm–3, consistent with other z ~ 2 galaxies but much higher than that in local Hxa0II regions. The star formation rate was estimated via the Hα luminosity, after correction for the lens magnification, to be about 365 ± 69 M ☉ yr–1. Combining the FWHM of Hα emission lines and the half-light radius, we found that the dynamical mass of the lensed galaxy is (5.8 ± 0.9) × 1010 M ☉. The gas mass is (5.1 ± 1.1) × 1010 M ☉ from the Hα flux surface density using global Kennicutt-Schmidt law, indicating a very high gas fraction of 0.79 ± 0.19 in J0900+2234.

Age spread in W3 main: Large Binocular Telescope/LUCI near-infrared spectroscopy of the massive stellar content

We present near-infrared multi-object spectroscopy and JHK(s) imaging of the massive stellar content of the Galactic star-forming region W3 Main, obtained with LUCI at the Large Binocular Telescope. We confirm 15 OB stars in W3 Main and derive spectral types between O5V and B4V from their absorption line spectra. Three massive young stellar objects are identified by their emission line spectra and near-infrared excess. The color-color diagram of the detected sources allows a detailed investigation of the slope of the near-infrared extinction law toward W3 Main. Analysis of the Hertzsprung-Russell diagram suggests that the Nishiyama extinction law fits the stellar population of W3 Main best (E(J -H)/ E(H - K-s) = 1.76 and RKs = 1.44). From our spectrophotometric analysis of the massive stars and the nature of their surrounding H II regions, we derive the evolutionary sequence of W3 Main and we find evidence of an age spread of at least 2-3 Myr. While the most massive star (IRS2) is already evolved, indications for high-mass pre-main-sequence evolution are found for another star (IRS N1), deeply embedded in an ultracompact H II (UCH II) region, in line with the different evolutionary phases observed in the corresponding H II regions. We derive a stellar mass of W3 Main of (4 +/- 1) x 10(3) M-circle dot by extrapolating from the number of OB stars using a Kroupa initial mass function and correcting for our spectroscopic incompleteness. We have detected the photospheres of OB stars from the more evolved diffuse H II region to the much younger UCH II regions, suggesting that these stars have finished their formation and cleared away their circumstellar disks very fast. Only in the hyper-compact H II region (IRS5) do the early-type stars seem to be still surrounded by circumstellar material.

Spectrum radial velocity analyser (SERVAL): High-precision radial velocities and two alternative spectral indicators

Context: The CARMENES survey is a high-precision radial velocity (RV) programme that aims to detect Earth-like planets orbiting low-mass stars. nAims: We develop least-squares fitting algorithms to derive the RVs and additional spectral diagnostics implemented in the SpEctrum Radial Velocity Analyser (SERVAL), a publicly available python code. nMethods: We measured the RVs using high signal-to-noise templates created by coadding all available spectra of each star.We define the chromatic index as the RV gradient as a function of wavelength with the RVs measured in the echelle orders. Additionally, we computed the differential line width by correlating the fit residuals with the second derivative of the template to track variations in the stellar line width. nResults: Using HARPS data, our SERVAL code achieves a RV precision at the level of 1m/s. Applying the chromatic index to CARMENES data of the active star YZ CMi, we identify apparent RV variations induced by stellar activity. The differential line width is found to be an alternative indicator to the commonly used full width half maximum. nConclusions: We find that at the red optical wavelengths (700--900 nm) obtained by the visual channel of CARMENES, the chromatic index is an excellent tool to investigate stellar active regions and to identify and perhaps even correct for activity-induced RV variations.

CARMENES input catalogue of M dwarfs - II. High-resolution imaging with FastCam

Aims. We search for low-mass companions of M dwarfs and characterize their multiplicity fraction with the purpose of helping in the selection of the most appropriate targets for the CARMENES exoplanet survey. Methods. We obtained high-resolution images in the I band with the lucky imaging instrument FastCam at the 1.5u2009m Telescopio Carlos Sanchez for 490 mid- to late-M dwarfs. For all the detected binaries, we measured angular separations, position angles, and magnitude differences in the I band. We also calculated the masses of each individual component and estimated orbital periods, using the available magnitude and colour relations for M dwarfs and our own M J -spectral type and mass- M I relations. To avoid biases in our sample selection, we built a volume-limited sample of M0.0-M5.0 dwarfs that is complete up to 86% within 14u2009pc. Results. From the 490 observed stars, we detected 80 companions in 76 systems, of which 30 are new discoveries. Another six companion candidates require additional astrometry to confirm physical binding. The multiplicity fraction in our observed sample is 16.7u2009±u20092.0%. The bias-corrected multiplicity fraction in our volume-limited sample is 19.5u2009±u20092.3% for angular separations of 0.2 to 5.0u2009arcsec (1.4−65.6u2009au), with a peak in the distribution of the projected physical separations at 2.5−7.5u2009au. For M0.0-M3.5u2009V primaries, our search is sensitive to mass ratios higher than 0.3 and there is a higher density of pairs with mass ratios over 0.8 compared to those at lower mass ratios. Binaries with projected physical separations shorter than 50u2009au also tend to be of equal mass. For 26 of our systems, we estimated orbital periods shorter than 50u2009a, 10 of which are presented here for the first time. We measured variations in angular separation and position angle that are due to orbital motions in 17 of these systems. The contribution of binaries and multiples with angular separations shorter than 0.2u2009arcsec, longer than 5.0u2009arcsec, and of spectroscopic binaries identified from previous searches, although not complete, may increase the multiplicity fraction of M dwarfs in our volume-limited sample to at least 36%.

Efficient scheduling of astronomical observations: Application to the CARMENES radial-velocity survey

We acknowledge financial support from the Spanish Ministry of Economy and Competitiveness (MINECO) through grants ESP2013-48391-C4-1-R, ESP2014-57495-C2-2-R, AYA2014-54348-C3-1-R and AYA2014-54348-C3-2-R. A.R. acknowledges support from the European Research Council under the FP7 Starting Grant agreement number 279347 and from DFG grant RE 1664/9-1.

The CARMENES search for exoplanets around M dwarfs: Radial-velocity variations of active stars in visual-channel spectra★

Previous simulations predicted the activity-induced radial-velocity (RV) variations of M dwarfs to range from

The CARMENES search for exoplanets around M dwarfs: Wing asymmetries of Hα, Na I D, and He I lines

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Stellar science from a blue wavelength range - A possible design for the blue arm of 4MOST

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Stellar science from a blue wavelength range

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