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.

A COMBINED SUBARU/VLT/MMT 1-5 μm STUDY OF PLANETS ORBITING HR 8799: IMPLICATIONS FOR ATMOSPHERIC PROPERTIES, MASSES, AND FORMATION

Abstract: We present new 1-1.25 micron (z and J band) Subaru/IRCS and 2 micron (K band) VLT/NaCo data for HR 8799 and a rereduction of the 3-5 micron MMT/Clio data first presented by Hinz et al. Our VLT/NaCo data yield a detection of a fourth planet at a projected separation of approximately 15 AU--"HR 8799e ." We also report new, albeit weak detections of HR 8799b at 1.03 micron and 3.3 micron. Empirical comparisons to field brown dwarfs show that at least HR 8799b and HR 8799c, and possibly HR 8799d, have near-to-mid-IR colors/ magnitudes significantly discrepant from the L/T dwarf sequence. Standard cloud deck atmosphere models appropriate for brown dwarfs provide only (marginally) statistically meaningful fits to HR 8799b and c for unphysically small radii. Models with thicker cloud layers not present in brown dwarfs reproduce the planets' spectral energy distributions far more accurately and without the need for resealing the planets' radii. Our preliminary modeling suggests that HR 8799b has log(g) = 4-4.5, T(sub eff) = 900 K. while HR 8799c, d, and (by inference) e have log(g) = 4-4.5, T(sub eff) = 1000-1200 K. Combining results from planet evolution models and new dynamical stability limits implies that the masses of HR 8799b, c, d, and e are 6-7 M(sub j), 7-10 M(sub j), 7-10 M(sub j), and 7-10 M(sub j). "Patchy" cloud prescriptions may provide even better fits to the data and may lower the estimated surface gravities and masses. Finally, contrary to some recent claims, forming the HR 8799 planets by core accretion is still plausible, although such systems are likely rare.

A very luminous magnetar-powered supernova associated with an ultra-long γ-ray burst

Abstract: A new class of ultra-long-duration (more than 10,000 seconds) γ-ray bursts has recently been suggested. They may originate in the explosion of stars with much larger radii than those producing normal long-duration γ-ray bursts or in the tidal disruption of a star. No clear supernova has yet been associated with an ultra-long-duration γ-ray burst. Here we report that a supernova (SN 2011kl) was associated with the ultra-long-duration γ-ray burst GRB 111209A, at a redshift z of 0.677. This supernova is more than three times more luminous than type Ic supernovae associated with long-duration γ-ray bursts, and its spectrum is distinctly different. The slope of the continuum resembles those of super-luminous supernovae, but extends further down into the rest-frame ultraviolet implying a low metal content. The light curve evolves much more rapidly than those of super-luminous supernovae. This combination of high luminosity and low metal-line opacity cannot be reconciled with typical type Ic supernovae, but can be reproduced by a model where extra energy is injected by a strongly magnetized neutron star (a magnetar), which has also been proposed as the explanation for super-luminous supernovae.

Near-coeval formation of the Galactic bulge and halo inferred from globular cluster ages

Abstract: THE morphology of our Galaxy is characterized by a disk of stars moving on circular orbits, surrounding a central spheroidal body of stars on high-velocity, randomly oriented orbits. The spheroid is further differentiated into an inner bulge and an outer halo; the bulge stars are rich in elements heavier than helium ('metals'), whereas the halo stars are metal-poor, suggesting that the latter formed very early in the history of the Galaxy. (They have experienced little chemical enrichment, by previous generations of stars.) It is not known, however, whether the bulge is the inner extension of the halo, having formed as part of the same process1, or whether it formed much later, perhaps by a dynamical distortion of the inner regions of the disk2,3. Here we report observations obtained with the Hubble Space Telescope of two metal-rich globular clusters that form part of the bulge population. Within the uncertainties, these bulge globular clusters appear to be coeval with halo clusters, which suggests that the formation of the bulge was part of the dynamical process that formed the halo, and that the bulge gas underwent rapid chemical enrichment, in less than a few billion years.

ALMA Spectroscopic Survey in the Hubble Ultra Deep Field: The Infrared Excess of UV-selected z=2-10 galaxies as a function of UV-continuum Slope and Stellar Mass

Abstract: We make use of deep 1.2 mm continuum observations (12.7 μJy beam−1 rms) of a 1 arcmin² region in the Hubble Ultra Deep Field to probe dust-enshrouded star formation from 330 Lyman-break galaxies spanning the redshift range z = 2–10 (to ∼2–3 M⊙ yr−1 at 1σ over the entire range). Given the depth and area of ASPECS, we would expect to tentatively detect 35 galaxies, extrapolating the Meurer z ∼ 0 IRX–β relation to z > 2 (assuming dust temperature Td ∼ 35 K). However, only six tentative detections are found at z >~ 2 in ASPECS, with just three at >3σ. Subdividing our z = 2–10 galaxy samples according to stellar mass, UV luminosity, and UV-continuum slope and stacking the results, we find a significant detection only in the most massive (>109.75 Me) subsample, with an infrared excess (IRX = LIR/LUV) consistent with previous z ∼ 2 results. However, the infrared excess we measure from our large selection of sub-L∗ ( ~ 2 galaxies. We find that the evolution of the IRX–stellar mass relationship depends on the evolution of the dust temperature. If the dust temperature increases monotonically with redshift (µ +1 z 0.32 ( ) ) such that Td ∼ 44–50 K at z 4, current results are suggestive of little evolution in this relationship to z ∼ 6. We use these results to revisit recent estimates of the z > 3 star formation rate density.

Are the hosts of gamma-ray bursts sub-luminous and blue galaxies?

Abstract: We present K-band imaging observations of ten gamma-ray burst (GRB) host galaxies for which an optical and/or radio afterglow associated with the GRB event was clearly identified. Data were obtained with the Very Large Telescope and New Technology Telescope at ESO (Chile), and with the Gemini-North telescope at Mauna Kea (Hawaii). Adding to our sample nine other GRB hosts with K-band photometry and determined redshifts published in the literature, we compare their observed and absolute K magnitudes as well as their R K colours with those of other distant sources detected in various optical, near- infrared, mid-infrared and submillimeter deep surveys. We find that the GRB host galaxies, most of them lying at 0:5< z< 1:5, exhibit very blue colours, comparable to those of the faint blue star-forming sources at high redshift. They are sub-luminous in the K-band, suggesting a low stellar mass content. We do not find any GRB hosts harbouring R -a ndK-band properties similar to those characterizing the luminous infrared/submillimeter sources and the extremely red starbursts. Should GRBs be regarded as an unbiased probe of star-forming activity, this lack of luminous and/or reddened objects among the GRB host sample might reveal that the detection of GRB optical afterglows is likely biased toward unobscured galaxies. It would moreover support the idea that a large fraction of the optically-dark GRBs occur within dust-enshrouded regions of star formation. On the other hand, our result might also simply reflect intrinsic properties of GRB host galaxies experiencing a first episode of very massive star formation and characterized by a rather weak underlying stellar population. Finally, we compute the absolute B magnitudes for the whole sample of GRB host galaxies with known redshifts and detected at optical wavelengths. We find that the latter appear statistically even less luminous than the faint blue sources which mostly contributed to the B-band light emitted at high redshift. This indicates that the formation of GRBs could be favoured in particular systems with very low luminosities and, therefore, low metallicities. Such an intrinsic bias toward metal-poor environments would be actually consistent with what can be expected from the currently-favoured scenario of the "collapsar". The forthcoming launch of the SWIFT mission at the end of 2003 will provide a dramatic increase of the number of GRB-selected sources. A detailed study of the chemical composition of the gas within this sample of galaxies will thus allow us to further analyse the potential eect of metallicity in the formation of GRB events.