European Southern Observatory

About: European Southern Observatory is a facility organization based out in Garching bei München, Germany. It is known for research contribution in the topics: Galaxy & Stars. The organization has 3594 authors who have published 16157 publications receiving 823095 citations. The organization is also known as: The European Southern Observatory，ESO & ESO.

The CARMENES search for exoplanets around M dwarfs - High-resolution optical and near-infrared spectroscopy of 324 survey stars

Abstract: The CARMENES radial velocity (RV) survey is observing 324 M dwarfs to search for any orbiting planets. In this paper, we present the survey sample by publishing one CARMENES spectrum for each M dwarf. These spectra cover the wavelength range 520–1710 nm at a resolution of at least R >80 000, and we measure its RV, Hα emission, and projected rotation velocity. We present an atlas of high-resolution M-dwarf spectra and compare the spectra to atmospheric models. To quantify the RV precision that can be achieved in low-mass stars over the CARMENES wavelength range, we analyze our empirical information on the RV precision from more than 6500 observations. We compare our high-resolution M-dwarf spectra to atmospheric models where we determine the spectroscopic RV information content, Q , and signal-to-noise ratio. We find that for all M-type dwarfs, the highest RV precision can be reached in the wavelength range 700–900 nm. Observations at longer wavelengths are equally precise only at the very latest spectral types (M8 and M9). We demonstrate that in this spectroscopic range, the large amount of absorption features compensates for the intrinsic faintness of an M7 star. To reach an RV precision of 1 m s−1 in very low mass M dwarfs at longer wavelengths likely requires the use of a 10 m class telescope. For spectral types M6 and earlier, the combination of a red visual and a near-infrared spectrograph is ideal to search for low-mass planets and to distinguish between planets and stellar variability. At a 4 m class telescope, an instrument like CARMENES has the potential to push the RV precision well below the typical jitter level of 3–4 m s−1 .

SN 2003du: 480 days in the life of a normal type Ia supernova

Abstract: Aims. We present a study of the optical and near-infrared (NIR) properties of the Type Ia Supernova (SN Ia) 2003du. Methods. An extensive set of optical and NIR photometry and low-resolution long-slit spectra was obtained using a number of facilities. The observations started 13 days before B-band maximum light and continued for 480 days with exceptionally good time sampling. The optical photometry was calibrated through the S-correction technique. Results. The UBVRIJHK light curves and the color indices of SN 2003du closely resemble those of normal SNeIa. SN 2003du reached a B-band maximum of 13.49 ± 0.02 mag on JD2 452 766.38 ± 0.5. We derive a B-band stretch parameter of 0.988 ± 0.003, which corresponds to Δm 15 = 1.02 ± 0.05, indicative of a SN Ia of standard luminosity. The reddening in the host galaxy was estimated by three methods, and was consistently found to be negligible. Using an updated calibration of the V and JHK absolute magnitudes of SNeIa, we find a distance modulus μ = 32.79 ± 0.15 mag to the host galaxy, UGC 9391. We measure a peak uvoir bolometric luminosity of 1.35(±0.20) x 10 43 erg s -1 and Arnett's rule implies that M 56Nι ≃ 0.68 ± 0.14M ⊙ of 56 Ni was synthesized during the explosion. Modeling of the uvoir bolometric light curve also indicates M56 Ni in the range 0.6-0.8 M ⊙ . The spectral evolution of SN 2003du at both optical and NIR wavelengths also closely resembles normal SNe Ia. In particular, the Si II ratio at maximum R(Si II) = 0.22 ± 0.02 and the time evolution of the blueshift velocities of the absorption line minima are typical. The pre-maximum spectra of SN 2003du showed conspicuous high-velocity features in the Call H&K doublet and infrared triplet, and possibly in Si II λ6355, lines. We compare the time evolution of the profiles of these lines with other well-observed SNe Ia and we suggest that the peculiar pre-maximum evolution of SiII λ6355 line in many SNe Ia is due to the presence of two blended absorption components.

Cold gas properties of the Herschel Reference Survey - II. Molecular and total gas scaling relations

Abstract: We study the properties of the cold gas component of the interstellar medium of the Herschel Reference Survey, a complete volume-limited (15 ≲ D ≲ 25 Mpc), K -band-selected sample of galaxies spanning a wide range in morphological type (from ellipticals to dwarf irregulars) and stellar mass (109 ≲ M star ≲ 1011 M ⊙ ). The multifrequency data in our hands are used to trace the molecular gas mass distribution and the main scaling relations of the sample, which put strong constraints on galaxy formation simulations. We extend the main scaling relations concerning the total and the molecular gas component determined for massive galaxies (M star ≳ 1010 M ⊙ ) from the COLD GASS survey down to stellar masses M star ≃ 109 M ⊙ . As scaling variables we use the total stellar mass M star , the stellar surface density μ star , the specific star formation rate SSFR, and the metallicity of the target galaxies. By comparing molecular gas masses determined using a constant or a luminosity dependent X CO conversion factor, we estimate the robustness of these scaling relations on the very uncertain assumptions used to transform CO line intensities into molecular gas masses. The molecular gas distribution of a K -band-selected sample is significantly different from that of a far-infrared-selected sample since it includes a significantly smaller number of objects with M (H2 ) ≲ 6 × 109 M ⊙ . In spiral galaxies the molecular gas phase is only 25–30% of the atomic gas. The analysis also indicates that the slope of the main scaling relations depends on the adopted conversion factor. Among the sampled relations, all those concerning M (gas)/M star are statistically significant and show little variation with X CO . We observe a significant correlation between M (H2 )/M star and SSFR, M (H2 )/M (Hi) and μ star , M (H2 )/M (Hi) and 12 + log (O/H), regardless of the adopted X CO . The total and molecular gas consumption timescales are anticorrelated with the specific star formation rate. The comparison of HRS and COLD GASS data indicates that some of the observed scaling relations are nonlinear.

Measuring the Redshift Evolution of Clustering: the Hubble Deep Field South

Abstract: ABSTRA C T We present an analysis of the evolution of galaxy clustering in the redshift interval 0 # z # 4:5 in the Hubble Deep Field South (HDF-South). The HST optical data are combined with infrared ISAAC/VLT observations, and photometric redshifts are used for all the galaxies brighter than IAB # 27:5. The clustering signal is obtained in different redshift bins using two different approaches: a standard one, which uses the best redshift estimate of each object, and a second one, which takes into account the redshift probability function of each object. This second method makes it possible to improve the information in the redshift intervals where contamination from objects with insecure redshifts is important. With both methods, we find that the clustering strength up to z . 3:5 in the HDF-South is consistent with the previous results in the HDF-North. Whereas at redshift lower than z , 1 the HDF galaxy population is un/anti-biasedOb # 1U with respect to the underlying dark matter, at high redshift the bias increases up to bOz , 3U . 2‐3, depending on the cosmological model. These results support previous claims that, at high redshift, galaxies are preferentially located in massive haloes, as predicted by the biased galaxy formation scenario. In order to quantify the impact of cosmic errors on our analyses, we have used analytical expressions from Bernstein. Once the behaviour of higher-order moments is assumed, our results show that errors in the clustering measurements in the HDF surveys are indeed dominated by pure shot-noise in most regimes, as assumed in our analysis. We also show that future observations with instruments like the Advanced Camera on HST will improve the signal-to-noise ratio by at least a factor of 2, as a consequence, more detailed analyses of the errors will be required. In fact, pure shot-noise will give a smaller contribution with respect to other sources of errors, such as finite volume effects or non-Poissonian discreteness effects.

The role of cold gas and environment on the stellar mass-metallicity relation of nearby galaxies

Abstract: We investigate the relationship between stellar mass, metallicity and gas content for a magnitude- and volume-limited sample of 260 nearby late-type galaxies in different environments, from isolated galaxies to Virgo cluster members. We derive oxygen abundance estimates using new integrated, drift-scan optical spectroscopy and the base metallicity calibrations of Kewley & Ellison (2008, ApJ, 681, 1183). Combining these measurements with ultraviolet to near-infrared photometry and Hi 21 cm line observations, we examine the relations between stellar mass, metallicity, gas mass fraction and star formation rate. We find that, at fixed stellar mass, galaxies with lower gas fractions typically also possess higher oxygen abundances. We also observe a relationship between gas fraction and metal content, whereby gas-poor galaxies are typically more metal-rich, and demonstrate that the removal of gas from the outskirts of spirals may increase the observed average metallicity by ∼0.1 dex. Although some cluster galaxies are gas-deficient objects, statistically the stellar-mass metallicity relation is nearly invariant to the environment, in agreement with recent studies. These results indicate that internal evolutionary processes, rather than environmental effects, play a key role in shaping the stellar mass-metallicity relation. In addition, we present metallicity estimates based on observations of 478 nearby galaxies.