bluuebunny/crossref_metadata_2025_split huggingface dataset:
HIGH-TIME RESOLUTION IN SITU INVESTIGATION OF MAJOR COMETARY VOLATILES AROUND 67P/C–G AT 3.1–2.3 au MEASURED WITH ROSINA-RTOF
Authors: Mall U. , Altwegg K. , Balsiger H. , Bar-Nun A. , Berthelier J.-J. , Bieler A. , Bochsler P. , Briois C. , Calmonte U. , Combi M. R. , Dabrowski B. , Keyser J. De , Dhooghe F. , Fiethe B. , Fuselier S. A. , Galli A. , Garnier P. , Gasc S. , Gombosi T. I. , Hansen K. C. , Hässig M. , Hoang M. , Jäckel A. , Kopp E. , Korth A. , Roy L. Le , Magee B. , Marty B. , Mousis O. , Rème H. , Rubin M. , Sémon T. , Tzou C.-Y. , Waite J. H. , Wurz P. 
Published: March 2016

ABSTRACT
Comets considered to be pristine objects contain key information about the early formation of the solar system. Their volatile components can provide clues about the origin and evolution of gases and ices in the comets. Measurements with ROSINA/RTOF at 67P/Churyumov–Gerasimenko have now allowed, for the first time, a direct in situ high-time resolution measurement of the most abundant cometary molecules originating directly from a comet’s nucleus over a long time-period, much longer than any previous measurements at a close distance to a comet between 3.1 and 2.3 au. We determine the local densities of H2O, CO2, and CO, and investigate their variabilities.
MASS–RADIUS RELATION FOR ROCKY PLANETS BASED ON PREM
Authors: Zeng Li , Sasselov Dimitar D. , Jacobsen Stein B. 
Published: March 2016

ABSTRACT
Several small dense exoplanets are now known, inviting comparisons to Earth and Venus. Such comparisons require translating their masses and sizes to composition models of evolved multi-layer interior planets. Such theoretical models rely on our understanding of the Earth’s interior, as well as independently derived equations of state, but so far have not involved direct extrapolations from Earth’s seismic model: the Preliminary Reference Earth Model (PREM). To facilitate more detailed compositional comparisons between small exoplanets and the Earth, we derive here a semi-empirical mass–radius relation for two-layer rocky planets based on PREM,

, where CMF stands for core mass fraction. It is applicable to 1 ∼ 8 M
⊕ and a CMF of 0.0 ∼ 0.4. Applying this formula to Earth and Venus and several known small exoplanets with radii and masses measured to better than ∼30% precision gives a CMF fit of 0.26 ± 0.07.
CONSTRAINING AGN FEEDBACK IN MASSIVE ELLIPTICALS WITH SOUTH POLE TELESCOPE MEASUREMENTS OF THE THERMAL SUNYAEV–ZEL’DOVICH EFFECT
Authors: Spacek Alexander , Scannapieco Evan , Cohen Seth , Joshi Bhavin , Mauskopf Philip 
Published: March 2016

ABSTRACT
Energetic feedback due to active galactic nuclei (AGNs) is likely to play an important role in the observed anti-hierarchical trend in the evolution of galaxies, and yet the energy injected into the circumgalactic medium by this process is largely unknown. One promising approach to constrain this feedback is through measurements of spectral distortions in the cosmic microwave background due to the thermal Sunyaev–Zeldovich (tSZ) effect, whose magnitude is directly proportional to the energy input by AGNs. With current instruments, making such measurements requires stacking large numbers of objects to increase signal-to-noise. While one possible target for such stacks is AGNs themselves, these are relatively scarce sources that contain contaminating emission that complicates tSZ measurements. Here we adopt an alternative approach and co-add South Pole Telescope SZ (SPT-SZ) survey data around a large set of massive quiescent elliptical galaxies at

, which are much more numerous and less contaminated than active AGNs, yet are subject to the same feedback processes from the AGNs they hosted in the past. We use data from the Blanco Cosmology Survey and VISTA Hemisphere Survey to create a large catalog of galaxies split up into two redshift bins: one with 3394 galaxies at

and one with 924 galaxies at

with typical stellar masses of

We then co-add the emission around these galaxies, resulting in a measured tSZ signal at

significance for the lower redshift bin and a contaminating signal at

for the higher redshift bin. To remove contamination due to dust emission, we use SPT-SZ source counts to model a contaminant source population in both the SPT-SZ bands and Planck high-frequency bands for a subset of 937 galaxies in the low-redshift bin and 240 galaxies in the high-redshift bin. This increases our detection to

for low redshifts and

for high redshifts. We find the mean angularly integrated Compton-y values to be

Mpc2 for low redshifts and

Mpc2 for high redshifts, corresponding to total thermal energies of

erg and

erg, respectively. These numbers are higher than expected from simple theoretical models that do not include AGN feedback, and serve as constraints that can be applied to current simulations of massive galaxy formation.
A REMARKABLY LUMINOUS GALAXY AT Z = 11.1 MEASURED WITH HUBBLE SPACE TELESCOPE GRISM SPECTROSCOPY
Authors: Oesch P. A. , Brammer G. , Dokkum P. G. van , Illingworth G. D. , Bouwens R. J. , Labbé I. , Franx M. , Momcheva I. , Ashby M. L. N. , Fazio G. G. , Gonzalez V. , Holden B. , Magee D. , Skelton R. E. , Smit R. , Spitler L. R. , Trenti M. , Willner S. P. 
Published: March 2016

ABSTRACT
We present Hubble WFC3/IR slitless grism spectra of a remarkably bright z ≳ 10 galaxy candidate, GN-z11, identified initially from CANDELS/GOODS-N imaging data. A significant spectroscopic continuum break is detected at

. The new grism data, combined with the photometric data, rule out all plausible lower redshift solutions for this source. The only viable solution is that this continuum break is the Lyα break redshifted to

, just ∼400 Myr after the Big Bang. This observation extends the current spectroscopic frontier by 150 Myr to well before the Planck (instantaneous) cosmic reionization peak at z ∼ 8.8, demonstrating that galaxy build-up was well underway early in the reionization epoch at z > 10. GN-z11 is remarkably, and unexpectedly, luminous for a galaxy at such an early time: its UV luminosity is 3× larger than

measured at z ∼ 6−8. The Spitzer IRAC detections up to 4.5 μm of this galaxy are consistent with a stellar mass of ∼109 M
⊙. This spectroscopic redshift measurement suggests that James Webb Space Telescope (JWST) will be able to similarly and easily confirm such sources at z > 10 and characterize their physical properties through detailed spectroscopy. Furthermore, WFIRST, with its wide-field near-IR imaging, would find large numbers of similar galaxies and contribute greatly to JWST's spectroscopy, if it is launched early enough to overlap with JWST.
CONSTRAINING THE DYNAMICAL IMPORTANCE OF HOT GAS AND RADIATION PRESSURE IN QUASAR OUTFLOWS USING EMISSION LINE RATIOS
Authors: Stern Jonathan , Faucher-Giguère Claude-André , Zakamska Nadia L. , Hennawi Joseph F. 
Published: March 2016

ABSTRACT
Quasar feedback models often predict an expanding hot gas bubble that drives a galaxy-scale outflow. In many circumstances this hot gas radiates inefficiently and is therefore difficult to observe directly. We present an indirect method to detect the presence of a hot bubble using hydrostatic photoionization calculations of the cold (

) line-emitting gas. We compare our calculations with observations of the broad line region, the inner face of the torus, the narrow line region (NLR), and the extended NLR, and thus constrain the hot gas pressure at distances

from the center. We find that emission line ratios observed in the average quasar spectrum are consistent with radiation-pressure-dominated models on all scales. On scales

a dynamically significant hot gas pressure is ruled out, while on larger scales the hot gas pressure cannot exceed six times the local radiation pressure. In individual quasars, ≈25% of quasars exhibit NLR ratios that are inconsistent with radiation-pressure-dominated models, although in these objects the hot gas pressure is also unlikely to exceed the radiation pressure by an order of magnitude or more. The derived upper limits on the hot gas pressure imply that the instantaneous gas pressure force acting on galaxy-scale outflows falls short of the time-averaged force needed to explain the large momentum fluxes

inferred for galaxy-scale outflows. This apparent discrepancy can be reconciled if optical quasars previously experienced a buried, fully obscured phase during which the hot gas bubble was more effectively confined and during which galactic wind acceleration occurred.
THE RADIAL AND ROTATIONAL VELOCITIES OF PSO J318.5338-22.8603, A NEWLY CONFIRMED PLANETARY-MASS MEMBER OF THE β PICTORIS MOVING GROUP
Authors: Allers K. N. , Gallimore J. F. , Liu Michael C. , Dupuy Trent J. 
Published: March 2016

ABSTRACT
PSO J318.5338−22.8603 is an extremely red planetary-mass object that has been identified as a candidate member of the β Pictoris moving group based on its spatial position and tangential velocity. We present a high-resolution K-band spectrum of PSO J318.5338−22.8603. Using a forward modeling Markov Chain Monte Carlo approach, we report the first measurement of the radial velocity and v sin(i) of PSO J318.5−22,

km s−1, and

km s−1, respectively. We calculate the space velocity and position of PSO J318.5−22 and confirm that it is a member of the β Pictoris moving group. Adopting an age of 23 ± 3 Myr for PSO J318.5−22, we determine a mass of 8.3 ± 0.5 M
Jup and an effective temperature of

K using evolutionary models. PSO J318.5338−22.8603 is intermediate in mass and temperature to the directly imaged planets β Pictoris b and 51 Eridani b, making it an important benchmark object in the sequence of the planetary-mass members of the β Pictoris moving group. Combining our v sin(i) measurement with recent photometric variability data, we constrain the inclination of PSO J318.5−22 to >29° and its rotational period to 5–10.2 hr. The equatorial velocity of PSO J318.5−22 indicates that its rotation is consistent with an extrapolation of the velocity–mass relationship for solar system planets.
ORION’S VEIL. IV. H2 EXCITATION AND GEOMETRY
Authors: Abel N. P. , Ferland G. J. , O’Dell C. R. , Troland T. H. 
Published: March 2016

ABSTRACT
The foreground Veil of material that lies in front of the Orion Nebula is the best studied sample of the interstellar medium because we know where it is located, how it is illuminated, and the balance of thermal and magnetic energy. In this work, we present high-resolution STIS observations toward the Trapezium, with the goal of better understanding the chemistry and geometry of the two primary Veil layers, along with ionized gas along the line of sight. The most complete characterization of the rotational/vibrational column densities of H2 in the almost purely atomic components of the Veil are presented, including updates to the Cloudy model for H2 formation on grain surfaces. The observed H2 is found to correlate almost exclusively with Component B. The observed H2, observations of CI, CI*, and CI**, and theoretical calculations using Cloudy allow us to place the tightest constraints yet on the distance, density, temperature, and other physical characteristics for each cloud component. We find the H2 excitation spectrum observed in the Veil is incompatible with a recent study that argued that the Veil was quite close to the Trapezium. The nature of a layer of ionized gas lying between the Veil and the Trapezium is characterized through the emission and absorption lines it produces, which we find to be the blueshifted component observed in S iii and P iii absorption. We deduce that, within the next 30–60 thousand years, the blueshifted ionized layer and Component B will merge, which will subsequently merge with Component A in the next one million years.
WHAT IS CONTROLLING THE FRAGMENTATION IN THE INFRARED DARK CLOUD G14.225–0.506?: DIFFERENT LEVELS OF FRAGMENTATION IN TWIN HUBS
Authors: Busquet Gemma , Estalella Robert , Palau Aina , Liu Hauyu Baobab , Zhang Qizhou , Girart Josep Miquel , de Gregorio-Monsalvo Itziar , Pillai Thushara , Anglada Guillem , Ho Paul T. P. 
Published: March 2016

ABSTRACT
We present observations of the 1.3 mm continuum emission toward hub-N and hub-S of the infrared dark cloud G14.225–0.506 carried out with the Submillimeter Array, together with observations of the dust emission at 870 and 350 μm obtained with APEX and CSO telescopes. The large-scale dust emission of both hubs consists of a single peaked clump elongated in the direction of the associated filament. At small scales, the SMA images reveal that both hubs fragment into several dust condensations. The fragmentation level was assessed under the same conditions and we found that hub-N presents 4 fragments while hub-S is more fragmented, with 13 fragments identified. We studied the density structure by means of a simultaneous fit of the radial intensity profile at 870 and 350 μm and the spectral energy distribution adopting a Plummer-like function to describe the density structure. The parameters inferred from the model are remarkably similar in both hubs, suggesting that density structure could not be responsible for determining the fragmentation level. We estimated several physical parameters, such as the level of turbulence and the magnetic field strength, and we found no significant differences between these hubs. The Jeans analysis indicates that the observed fragmentation is more consistent with thermal Jeans fragmentation compared with a scenario in which turbulent support is included. The lower fragmentation level observed in hub-N could be explained in terms of stronger UV radiation effects from a nearby H ii region, evolutionary effects, and/or stronger magnetic fields at small scales, a scenario that should be further investigated.
CARBON CHAINS AND METHANOL TOWARD EMBEDDED PROTOSTARS*
Authors: Graninger Dawn M. , Wilkins Olivia H. , Öberg Karin I. 
Published: March 2016

ABSTRACT
Large interstellar organic molecules are potential precursors of prebiotic molecules. Their formation pathways and chemical relationships with one another and simpler molecules are therefore of great interest. In this paper we address the relationships between two classes of large organic molecules, carbon chains and saturated complex organic molecules at the early stages of star formation through observations of C4H and CH3OH. We surveyed these molecules with the IRAM 30 m telescope toward 16 deeply embedded low-mass protostars selected from the Spitzer c2d ice survey. We find that CH3OH and C4H are positively correlated, indicating that these two classes of molecules can coexist during the embedded protostellar stage. The C4H/CH3OH gas abundance ratio tentatively correlates with the CH4/CH3OH ice abundance ratio in the same lines of sight. This relationship supports a scenario where carbon chain formation in protostellar envelopes begins with CH4 ice desorption.
TOWARD THE ASTRONOMICAL DETECTION OF THE PROTON-BOUND COMPLEX NN–HCO+: IMPLICATIONS FOR THE SPECTRA OF PROTOPLANETARY DISKS
Authors: Fortenberry Ryan C. , Francisco Joseph S. , Lee Timothy J. 
Published: March 2016

ABSTRACT
Proton-bound complexes have been hypothesized as further means of detecting the nitrogen molecule in the interstellar medium. The study of such complexes has largely been hindered by the necessary experimental setups utilized or by their difficulty in producing and/or analyzing computed potential energy surfaces. Here the NN–HCO+ proton-bound complex is analyzed via quartic force fields (QFFs). While QFFs have produced meaningful results for other proton-bound complexes, they have been hindered by double-well potentials or flat potential surfaces. NN–HCO+ is not affected by these constraints. This strongly dipolar (3.63 D) molecule can be observed rotationally unlike the more heavily analyzed OCHCO+ and NNHNN+ proton-bound complexes. Additionally, the large absorption feature corresponding to the proton motion, a hallmark of proton-bound complexes, is much higher in frequency at 2547.1 cm−1, changing the range of experimental observation for the bright frequency. NN–HCO+ is hypothesized to be present in protoplanetary disks where N2H+ and CO are known. As such, it may help to influence the nitrogen budget of planet-forming astronomical regions.
CONTRACTION SIGNATURES TOWARD DENSE CORES IN THE PERSEUS MOLECULAR CLOUD
Authors: Campbell J. L. , Friesen R. K. , Martin P. G. , Caselli P. , Kauffmann J. , Pineda J. E. 
Published: March 2016

ABSTRACT
We report the results of an HCO+ (3–2) and N2D+ (3–2) molecular line survey performed toward 91 dense cores in the Perseus molecular cloud using the James Clerk Maxwell Telescope, to identify the fraction of starless and protostellar cores with systematic radial motions. We quantify the HCO+ asymmetry using a dimensionless asymmetry parameter δ

v
, and identify 20 cores with significant blue or red line asymmetries in optically thick emission indicative of collapsing or expanding motions, respectively. We separately fit the HCO+ profiles with an analytic collapse model and determine contraction (expansion) speeds toward 22 cores. Comparing the δ

v
and collapse model results, we find that δ

v
is a good tracer of core contraction if the optically thin emission is aligned with the model-derived systemic velocity. The contraction speeds range from subsonic (0.03 km s−1) to supersonic (0.4 km s−1), where the supersonic contraction speeds may trace global rather than local core contraction. Most cores have contraction speeds significantly less than their free-fall speeds. Only 7 of 28 starless cores have spectra well-fit by the collapse model, which more than doubles (15 of 28) for protostellar cores. Starless cores with masses greater than the Jeans mass (M/M
J > 1) are somewhat more likely to show contraction motions. We find no trend of optically thin non-thermal line width with M/M
J, suggesting that any undetected contraction motions are small and subsonic. Most starless cores in Perseus are either not in a state of collapse or expansion, or are in a very early stage of collapse.
MOLECULAR DISTRIBUTION IN THE SPIRAL ARM OF M51
Authors: Watanabe Yoshimasa , Sakai Nami , Sorai Kazuo , Ueda Junko , Yamamoto Satoshi 
Published: March 2016

ABSTRACT
Molecular line images of 13CO, C18O, CN, CS, CH3OH, and HNCO are obtained toward the spiral arm of M51 at a

resolution with the Combined Array for Research in Millimeter-wave Astronomy. Distributions of the molecules averaged over a 300 pc scale are found to be almost similar to one another and to essentially trace the spiral arm. However, the principal component analysis shows a slight difference of distributions among molecular species, particularly for CH3OH and HNCO. These two species do not correlate well with the star formation rate, implying that they are not enhanced by local star formation activities but by galactic-scale phenomena such as spiral shocks. Furthermore, the distributions of HNCO and CH3OH are found to be slightly different, and their origins deserve further investigation. The present results provide us with an important clue for understanding the 300 pc scale chemical composition in the spiral arm and its relation to galactic-scale dynamics.
UNIFIED MICROSCOPIC–MACROSCOPIC MONTE CARLO SIMULATIONS OF COMPLEX ORGANIC MOLECULE CHEMISTRY IN COLD CORES
Authors: Chang Qiang , Herbst Eric 
Published: March 2016

ABSTRACT
The recent discovery of methyl formate and dimethyl ether in the gas phase of cold cores with temperatures as cold as 10 K challenges our previous astrochemical models concerning the formation of complex organic molecules (COMs). The strong correlation between the abundances and distributions of methyl formate and dimethyl ether further shows that current astrochemical models may be missing important chemical processes in cold astronomical sources. We investigate a scenario in which COMs and the methoxy radical can be formed on dust grains via a so-called chain reaction mechanism, in a similar manner to CO2. A unified gas-grain microscopic–macroscopic Monte Carlo approach with both normal and interstitial sites for icy grain mantles is used to perform the chemical simulations. Reactive desorption with varying degrees of efficiency is included to enhance the nonthermal desorption of species formed on cold dust grains. In addition, varying degrees of efficiency for the surface formation of methoxy are also included. The observed abundances of a variety of organic molecules in cold cores can be reproduced in our models. The strong correlation between the abundances of methyl formate and dimethyl ether in cold cores can also be explained. Nondiffusive chemical reactions on dust grain surfaces may play a key role in the formation of some COMs.
EVOLUTION OF MAGNETIC HELICITY AND ENERGY SPECTRA OF SOLAR ACTIVE REGIONS
Authors: Zhang Hongqi , Brandenburg Axel , Sokoloff D. D. 
Published: March 2016

ABSTRACT
We adopt an isotropic representation of the Fourier-transformed two-point correlation tensor of the magnetic field to estimate the magnetic energy and helicity spectra as well as current helicity spectra of two individual active regions (NOAA 11158 and NOAA 11515) and the change of the spectral indices during their development as well as during the solar cycle. The departure of the spectral indices of magnetic energy and current helicity from 5/3 are analyzed, and it is found that it is lower than the spectral index of the magnetic energy spectrum. Furthermore, the fractional magnetic helicity tends to increase when the scale of the energy-carrying magnetic structures increases. The magnetic helicity of NOAA 11515 violates the expected hemispheric sign rule, which is interpreted as an effect of enhanced field strengths at scales larger than 30–60 Mm with opposite signs of helicity. This is consistent with the general cycle dependence, which shows that around the solar maximum the magnetic energy and helicity spectra are steeper, emphasizing the large-scale field.
UNRAVELING THE COMPLEX STRUCTURE OF AGN-DRIVEN OUTFLOWS. I. KINEMATICS AND SIZES
Authors: Karouzos Marios , Woo Jong-Hak , Bae Hyun-Jin 
Published: March 2016

ABSTRACT
Outflows driven by active galactic nuclei (AGNs) are often invoked as agents of the long-sought AGN feedback. Yet, characterizing and quantifying the impact on their host galaxies has been challenging. We present Gemini Multi-Object Spectrograph integral field unit data of six local (z

) and luminous (L

erg s−1) type 2 AGNs. In the first of a series of papers, we investigate the kinematics and constrain the size of the outflows. The ionized gas kinematics can be described as a superposition of a gravitational component that follows the stellar motion and an outflow-driven component that shows large velocity (up to 600 km s−1) and large velocity dispersion (up to 800 km s−1). Using the spatially resolved measurements of the gas, we kinematically measure the size of the outflow, which is found to be between 1.3 and 2.1 kpc. Owing to the lack of a detailed kinematic analysis, previous outflow studies likely overestimate their size by up to more than a factor of two, depending on how the size is estimated and whether the [O iii] or Hα emission line is used. The relatively small size of the outflows for all six of our objects casts doubts on their potency as a mechanism for negative AGN feedback.