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Cluster-formation in the Rosette molecular cloud at the junctions of filaments
Hill, T.; André, Ph.; Arzoumanian, D. +31 more
Aims: For many years feedback processes generated by OB-stars in molecular clouds, including expanding ionization fronts, stellar winds, or UV-radiation, have been proposed to trigger subsequent star formation. However, hydrodynamic models including radiation and gravity show that UV-illumination has little or no impact on the global dynamica…
A Revised Parallel-sequence Morphological Classification of Galaxies: Structure and Formation of S0 and Spheroidal Galaxies
Kormendy, John; Bender, Ralf
We update van den Bergh's parallel-sequence galaxy classification in which S0 galaxies form a sequence S0a-S0b-S0c that parallels the sequence Sa-Sb-Sc of spiral galaxies. The ratio B/T of bulge-to-total light defines the position of a galaxy in this tuning-fork diagram. Our classification makes one major improvement. We extend the S0a-S0b-S0c seq…
A magnified young galaxy from about 500 million years after the Big Bang
Donahue, Megan; Broadhurst, Tom; Kelson, Daniel D. +33 more
Re-ionization of the intergalactic medium occurred in the early Universe at redshift z ~ 6-11, following the formation of the first generation of stars. Those young galaxies (where the bulk of stars formed) at a cosmic age of less than about 500 million years (z <~ 10) remain largely unexplored because they are at or beyond the sensitivity limi…
Differential emission measures from the regularized inversion of Hinode and SDO data
Hannah, I. G.; Kontar, E. P.
Aims: To demonstrate the capabilities of regularized inversion to recover differential emission measures (DEMs) from multi-wavelength observations provided by telescopes such as Hinode and SDO.
Methods: We develop and apply an enhanced regularization algorithm, used in RHESSI X-ray spectral analysis, to constrain the ill-posed inverse pr…
Using the Bright Ultrahard XMM-Newton survey to define an IR selection of luminous AGN based on WISE colours
Stern, D.; Barcons, X.; Blain, A. +7 more
We present a highly complete and reliable mid-infrared (MIR) colour selection of luminous active galactic nucleus (AGN) candidates using the 3.4, 4.6 and 12 µm bands of the Wide-field Infrared Survey Explorer (WISE) survey. The MIR colour wedge was defined using the wide-angle Bright Ultrahard XMM-Newton survey (BUXS), one of the largest com…
Keck Spectroscopy of Faint 3 < z < 8 Lyman Break Galaxies: Evidence for a Declining Fraction of Emission Line Sources in the Redshift Range 6 < z < 8
Richard, Johan; Stark, Daniel P.; Ellis, Richard S. +5 more
Using deep Keck spectroscopy of Lyman break galaxies selected from infrared imaging data taken with the Wide Field Camera 3 on board the Hubble Space Telescope, we present new evidence for a reversal in the redshift-dependent fraction of star-forming galaxies with detectable Lyman alpha (Lyα) emission in the redshift range 6.3 < z < 8.8. Our…
What Turns Galaxies Off? The Different Morphologies of Star-forming and Quiescent Galaxies since z ~ 2 from CANDELS
Papovich, Casey; Bell, Eric F.; Giavalisco, Mauro +21 more
We use HST/WFC3 imaging from the CANDELS Multi-Cycle Treasury Survey, in conjunction with the Sloan Digital Sky Survey, to explore the evolution of galactic structure for galaxies with stellar masses >3 × 1010 M ⊙ from z = 2.2 to the present epoch, a time span of 10 Gyr. We explore the relationship between rest-frame optic…
The Characteristic Star Formation Histories of Galaxies at Redshifts z ~ 2-7
Pettini, Max; Erb, Dawn K.; Shapley, Alice E. +3 more
A large sample of spectroscopically confirmed star-forming galaxies at redshifts 1.4 <= z spec <= 3.7, with complementary imaging in the near- and mid-IR from the ground and from the Hubble Space Telescope and Spitzer Space Telescope, is used to infer the average star formation histories (SFHs) of typical galaxies from z ~ 2 to 7.…
Lower-luminosity Galaxies Could Reionize the Universe: Very Steep Faint-end Slopes to the UV Luminosity Functions at z >= 5-8 from the HUDF09 WFC3/IR Observations
Trenti, M.; Oesch, P. A.; Carollo, C. M. +7 more
The HUDF09 data are the deepest near-IR observations ever, reaching to 29.5 mag. Luminosity functions (LFs) from these new HUDF09 data for 132 z ~ 7 and z ~ 8 galaxies are combined with new LFs for z ~ 5-6 galaxies and the earlier z ~ 4 LF to reach to very faint limits (<0.05 L* z = 3). The faint-end slopes α are steep: -1.79 ± 0.12 …
Properties of Ground Level Enhancement Events and the Associated Solar Eruptions During Solar Cycle 23
Gopalswamy, N.; Yashiro, S.; Mäkelä, P. +3 more
Solar cycle 23 witnessed the most complete set of observations of coronal mass ejections (CMEs) associated with the Ground Level Enhancement (GLE) events. We present an overview of the observed properties of the GLEs and those of the two associated phenomena, viz., flares and CMEs, both being potential sources of particle acceleration. Although we…