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.

Discovery of an active galactic nucleus driven molecular outflow in the local early-type galaxy NGC 1266

Abstract: We report the discovery of a powerful molecular wind from the nucleus of the non-interacting nearby S0 field galaxy NGC 1266. The single-dish CO profile exhibits emission to ?400?km?s?1 and requires a nested Gaussian fit to be properly described. Interferometric observations reveal a massive, centrally concentrated molecular component with a mass of 1.1 ? 109 M ? and a molecular outflow with a molecular mass of 2.4 ? 107 M ?. The molecular gas close to the systemic velocity consists of a rotating, compact nucleus with a mass of about 4.1 ? 108 M ? within a radius of 60?pc. This compact molecular nucleus has a surface density of 2.7 ? 104 M ??pc?2, more than two orders of magnitude larger than that of giant molecular clouds in the disk of the Milky Way, and it appears to sit on the Kennicutt-Schmidt relation despite its extreme kinematics and energetic activity. We interpret this nucleus as a disk that confines the outflowing wind. A mass outflow rate of 13 M ? yr?1 leads to a depletion timescale of 85 Myr. The star formation in NGC 1266 is insufficient to drive the outflow, and thus it is likely driven by the active galactic nucleus. The concentration of the majority of the molecular gas in the central 100?pc requires an extraordinary loss of angular momentum, but no obvious companion or interacting galaxy is present to enable the transfer. NGC 1266 is the first known outflowing molecular system that does not show any evidence of a recent interaction.

Spectroscopic Confirmation of z ~ 7 Lyman Break Galaxies: Probing the Earliest Galaxies and the Epoch of Reionization

Abstract: We present the final results from our ultra-deep spectroscopic campaign with FORS2 at the ESO Very Large Telescope (VLT) for the confirmation of z {approx_equal} 7 'z-band dropout' candidates selected from our VLT/Hawk-I imaging survey over three independent fields. In particular, we report on two newly discovered galaxies at redshift {approx}6.7 in the New Technology Telescope Deep Field. Both galaxies show an Ly{alpha} emission line with rest-frame equivalent widths (EWs) of the order of 15-20 A and luminosities of (2-4) Multiplication-Sign 10{sup 42} erg s{sup -1}. We also present the results of ultra-deep observations of a sample of i-dropout galaxies, from which we set a solid upper limit on the fraction of interlopers. Out of the 20 z-dropouts observed we confirm 5 galaxies at 6.6 < z < 7.1. This is systematically below the expectations drawn on the basis of lower redshift observations: in particular, there is a significant lack of objects with intermediate Ly{alpha} EWs (between 20 and 55 A). We conclude that the observed trend for the rising fraction of Ly{alpha} emission in Lyman break galaxies from z {approx} 3 to z {approx} 6 is most probably reversed from z {approx} 6 to z {approx} 7. Explaining themore » observed rapid change in the Ly{alpha} emitter fraction among the dropout population with reionization requires a fast evolution of the neutral fraction of hydrogen in the universe. Assuming that the universe is completely ionized at z = 6 and adopting a set of semi-analytical models, we find that our data require a change of the neutral hydrogen fraction of the order of {Delta}{chi}{sub H{sub i}}{approx}0.6 in a time {Delta}z {approx} 1, provided that the escape fraction does not increase dramatically over the same redshift interval.« less

The K20 survey. VI. The distribution of the stellar masses in galaxies up to z 2

Abstract: We present a detailed analysis of the stellar mass content of galaxies up to as obtained from the K20 spectrophotometric galaxy sample. We have applied and compared two different methods to estimate the stellar mass from broad-band photometry: a Maximal Age approach, where we maximize the age of the stellar population to obtain the maximal mass compatible with the observed color, and a Best Fit model, where the best-fitting spectrum to the complete multicolor distribution is used. We find that the ratio decreases with redshift: in particular, the average ratio of early type galaxies decreases with z , with a scatter that is indicative of a range of star-formation time-scales and redshift of formation. More important, the typical ratio of massive early type galaxies is larger than that of less massive ones, suggesting that their stellar population formed at higher z . We show that the final K20 galaxy sample spans a range of stellar masses from to : massive galaxies () are common at , and are detected also up to . We compute the Galaxy Stellar Mass Function at various z, of which we observe only a mild evolution (i.e. by 20–30%) up to . At , the evolution in the normalization of the GSMF appears to be much faster: at , about 35% of the present day stellar mass in objects with appear to have assembled. We also detect a change in the physical nature of the most massive galaxies: at , all galaxies with are early type, while at higher z a population of massive star-forming galaxies progressively appears. We finally analyze our results in the framework of Λ -CDM hierarchical models. First, we show that the large number of massive galaxies detected at high z does not violate any fundamental Λ -CDM constraint based on the number of massive DM halos. Then, we compare our results with the predictions of several renditions of both semianalytic as well as hydro-dynamical models. The predictions from these models range from severe underestimates to slight overestimates of the observed mass density at ≤ 2. We discuss how the differences among these models are due to the different implementation of the main physical processes.

HST color-magnitude diagrams of 74 galactic globular clusters in the HST F439W and F555W bands ⋆

Abstract: We present the complete photometric database and the color-magnitude diagrams for 74 Galactic globular clusters observed with the HST/WFPC2 camera in the F439W and F555W bands. A detailed discussion of the various reduction steps is also presented, and of the procedures to transform instrumental magnitudes into both the HST F439W and F555W flight system and the standard Johnson B and V systems. We also describe the artificial star experiments which have been performed to derive the star count completeness in all the relevant branches of the color magnitude diagram. The entire photometric database and the completeness function will be made available on the Web immediately after the publication of the present paper.

H0LiCOW – IX. Cosmographic analysis of the doubly imaged quasar SDSS 1206+4332 and a new measurement of the Hubble constant

Abstract: We present a blind time-delay strong lensing (TDSL) cosmographic analysis of the doubly imaged quasar SDSS 1206+4332 We combine the relative time delay between the quasar images, Hubble Space Telescope imaging, the Keck stellar velocity dispersion of the lensing galaxy, and wide-field photometric and spectroscopic data of the field to constrain two angular diameter distance relations The combined analysis is performed by forward modelling the individual data sets through a Bayesian hierarchical framework, and it is kept blind until the very end to prevent experimenter bias After unblinding, the inferred distances imply a Hubble constant H_0 = 688|$^{+54}_{-51}$| km s^−1 Mpc^−1, assuming a flat Λ cold dark matter cosmology with uniform prior on Ω_m in [005, 05] The precision of our cosmographic measurement with the doubly imaged quasar SDSS 1206+4332 is comparable with those of quadruply imaged quasars and opens the path to perform on selected doubles the same analysis as anticipated for quads Our analysis is based on a completely independent lensing code than our previous three H0LiCOW systems and the new measurement is fully consistent with those We provide the analysis scripts paired with the publicly available software to facilitate independent analysis (footnote with link to wwwh0licoworg) The consistency between blind measurements with independent codes provides an important sanity check on lens modelling systematics By combining the likelihoods of the four systems under the same prior, we obtain H_0 = 725|$^{+21}_{-23}$| km s^−1 Mpc^−1 This measurement is independent of the distance ladder and other cosmological probes