bluuebunny/crossref_metadata_2025_split huggingface dataset:
Spin-down induced quark-hadron phase transition in cold isolated neutron stars
Authors: Prasad R , Mallick Ritam 
Published: August 2022

ABSTRACT
We have studied the spin-down induced phase transition (PT) in cold, isolated neutron stars in this work. After birth, as the star slows down, its central density rises and crosses the critical density of PT, and a quark core is seeded inside the star. Intermediate-mass stars are more likely to have a quark seeding in their lifetime at birth. Smaller neutron stars do not have a quark core and remain neutron stars throughout their life, whereas in massive stars, a quark core exists at their centre from birth. In intermediate and massive stars, the quark core grows further as the star slows down. The appearance of a quark core leads to a sudden change in the moment of inertia of the star in its evolutionary history, and is also reflected in a sudden discontinuity in the braking index of the star (at the frequency where the quark core first seeds). The energy released during the PT process as the quark core is seeded can excite the f-mode oscillation in the star and is emitted in the form of the gravitational wave, which is in the range of detection with present operating detectors; however, future detectors will enable a more clean extraction of this signals. Also, neutrinos and bursts of gamma-rays can originate from PT events. The spin-down induced PT could be gradual or in the form of subsequent leaps producing persistent or multiple transient emissions.
Primordial magnetic fields in Population III star formation: a magnetized resolution study
Authors: Prole Lewis R , Clark Paul C , Klessen Ralf S , Glover Simon C O , Pakmor Rüdiger 
Published: August 2022

ABSTRACT
Population III (Pop III) stars form in groups due to the fragmentation of primordial gas. While uniform magnetic fields have been shown to support against fragmentation in present-day star formation, it is unclear whether realistic k3/2 primordial fields can have the same effect. We bypass the issues associated with simulating the turbulent dynamo by introducing a saturated magnetic field at equipartition with the velocity field when the central densities reach 10−13 g cm−3. We test a range of sink particle creation densities from 10−10 to 10−8 g cm−3. Within the range tested, the fields did not suppress fragmentation of the gas and hence could not prevent the degree of fragmentation from increasing with increased resolution. The number of sink particles formed and total mass in sink particles was unaffected by the magnetic field across all seed fields and resolutions. The magnetic pressure remained sub-dominant to the gas pressure except in the highest density regions of the simulation box, where it became equal to but never exceeded gas pressure. Our results suggest that the inclusion of magnetic fields in numerical simulations of Pop III star formation is largely unimportant.
The role of rotation on the formation of second generation stars in globular clusters
Authors: Lacchin E , Calura F , Vesperini E , Mastrobuono-Battisti A 
Published: August 2022

ABSTRACT
By means of 3D hydrodynamic simulations, we explore the effects of rotation in the formation of second-generation (SG) stars in globular clusters (GC). Our simulations follow the SG formation in a first-generation (FG) internally rotating GC; SG stars form out of FG asymptotic giant branch (AGB) ejecta and external pristine gas accreted by the system. We have explored two different initial rotational velocity profiles for the FG cluster and two different inclinations of the rotational axis with respect to the direction of motion of the external infalling gas, whose density has also been varied. For a low (10−24 g cm−3) external gas density, a disc of SG helium-enhanced stars is formed. The SG is characterized by distinct chemo-dynamical phase space patterns: it shows a more rapid rotation than the FG with the helium-enhanced SG subsystem rotating more rapidly than the moderate helium-enhanced one. In models with high external gas density ($10^{-23}\, {\rm g\ cm^{-3}}$), the inner SG disc is disrupted by the early arrival of external gas and only a small fraction of highly enhanced helium stars preserves the rotation acquired at birth. Variations in the inclination angle between the rotation axis and the direction of the infalling gas and the velocity profile can slightly alter the extent of the stellar disc and the rotational amplitude. The results of our simulations illustrate the complex link between dynamical and chemical properties of multiple populations and provide new elements for the interpretation of observational studies and future investigations of the dynamics of multiple-population GCs.
Improving black hole accretion treatment in hydrodynamical simulations
Authors: Tartėnas Matas , Zubovas Kastytis 
Published: August 2022

ABSTRACT
The large-Galactic scales are connected to the many orders of magnitude smaller supermassive black hole (SMBH) scales by an episodic cycle of feeding and feedback. Active Galactic nuclei (AGN) are powered by accretion on to SMBH and the majority of AGN energy in near-Eddington regime is produced in thin subpc accretion discs. Currently, it is very difficult to model processes that occur on vastly different scales, ranging from the circumnuclear gas reservoirs at tens to hundreds of parsecs down to the accretion disc scales at &lt;0.01 pc. While subgrid prescriptions used in large-scale or cosmological simulations are able to reproduce large-scale feedback, we propose using a more realistic model in parsec-scale simulations, where it is important to get accurate time-scales to understand how feedback affects gas dynamics and star formation in the vicinity of the AGN. To test our approach we use a subresolution thin accretion disc model coupled to the SMBH in a set of hydrodynamical simulations of a retrograde collision between a gas ring and a molecular cloud in an environment similar to the Galactic Centre using the SPH code Gadget-3. The disc-mediated feeding of the SMBH is relatively smooth and delayed compared to an instantaneous feeding prescription. While the reduction of accretion due to feedback is present in both accretion disc and instantaneous feeding simulations, a clear central cavity appears only in accretion disc runs – hinting that a less volatile accretion phase could have a greater impact on the surrounding gas.
Ionized filaments and ongoing physical processes in massive-star-forming sites around l = 345.°5
Authors: Dewangan L K , Pirogov L E , Bhadari N K , Maity A K 
Published: August 2022

ABSTRACT
Numerous research studies on dust and molecular filaments in star-forming sites have been conducted, but only a limited number have focused on ionized filaments. To observationally study this aspect, we present an analysis of multiwavelength data from an area of ∼74.6 arcmin × 55 arcmin around l = 345${_{.}^{\circ}}$5. Using the 843-MHz continuum map, two distinct ionized filaments, namely IF-A (extent ∼8.5 arcmin) and IF-B (extent ∼22.65 arcmin), hosting ionized clumps powered by massive OB stars are identified. Using the 13CO(2–1) and C18O(2–1) line data, the parent molecular clouds of IF-A and IF-B are studied in the velocity range [−21, −10] km s−1, and found to have filamentary appearances. At least two cloud components around −18 and −15 km s−1 towards the parent clouds of IF-A and IF-B are investigated and are found to be connected in velocity space. These filamentary clouds also overlap spatially along the major axis, supporting the filamentary twisting/coupling nature. Noticeable Class I protostars and massive stars appear to be observed towards the common zones of the cloud components. These findings support the collision of two filamentary clouds about 1.2 Myr ago. The existence of the ionized filaments seems to be explained by the combined feedback of massive stars. The molecular filaments associated with IF-A and IF-B favour the outcomes of the most recent model concerning the escape and the trapping of the ionizing radiation from an O star formed in a filament.
The proper motion of stars in dwarf galaxies: distinguishing central density cusps from cores
Authors: de Martino Ivan , Diaferio Antonaldo , Ostorero Luisa 
Published: August 2022

ABSTRACT
We show that measuring the proper motion of ∼2000 stars within a dwarf galaxy, with an uncertainty of 1 km s−1 at most, can establish whether the dark matter (DM) density profile of the dwarf has a central core or cusp. We derive these limits by building mock star catalogues similar to those expected from future astrometric Theia-like missions and including celestial coordinates, radial velocity and proper motion of the stars. The density field of the DM halo of the dwarf is sampled from an extended Navarro–Frank–White (eNFW ) spherical model, whereas the number density distribution of the stars is a Plummer sphere. The velocity field of the stars is set according to the Jeans equations. A Monte Carlo Markov chain algorithm applied to a sample of N ≳ 2000 stars returns unbiased estimates of the eNFW DM parameters within $10{{\ \rm per\, cent}}$ of the true values and with 1σ relative uncertainties ≲ 20 per cent. The proper motions of the stars lift the degeneracy among the eNFW parameters which appears when the line-of-sight velocities alone are available. Our analysis demonstrates that, by estimating the log-slope of the mass density profile estimated at the half-light radius, a sample of N = 2000 stars can distinguish between a core and a cusp at more than 8σ. Proper motions also return unbiased estimates of the dwarf mass profile with 1σ uncertainties that decrease, on average, from 2.65 dex to 0.15 dex when the size of the star sample increases from N = 100 to N = 6000 stars. The measure of the proper motions can thus strongly constrain the distribution of DM in nearby dwarfs and provides fundamental contribution to understanding the nature and the properties of DM.
Propagation time delay and frame dragging effects of lightlike geodesics in the timing of a pulsar orbiting SgrA*
Authors: Ben-Salem Bilel , Hackmann Eva 
Published: August 2022

ABSTRACTTiming a pulsar in a close orbit around the supermassive black hole SgrA* at the centre of the Milky Way would open the window for an accurate determination of the black hole parameters and for new tests of general relativity and alternative modified gravity theories. An important relativistic effect which has to be taken into account in the timing model is the propagation delay of the pulses in the gravitational field of the black hole. Due to the extreme mass ratio of the pulsar and the supermassive back hole we use the test particle limit to derive an exact analytical formula for the propagation delay of lightlike geodesics in a Kerr space–time, and deduce a relativistic formula for the corresponding frame dragging effect on the arrival time. As an illustration, we treat an edge-on orbit in which the frame dragging effect on the emitted lightlike geodesics is expected to be maximal. We compare our formula for the propagation time delay with Post-Newtonian approaches, and in particular with the frame dragging terms derived in previous works by Wex & Kopeikin and Rafikov & Lai. Our approach correctly identifies the asymmetry of the frame dragging delay with respect to superior conjunction, avoids singularities in the time delay, and indicates that in the Post-Newtonian approach frame dragging effects on the lightlike pulses are generally slightly overestimated.
Environmental dependence of the molecular cloud lifecycle in 54 main-sequence galaxies
Authors: Kim Jaeyeon , Chevance Mélanie , Kruijssen J M Diederik , Leroy Adam K , Schruba Andreas , Barnes Ashley T , Bigiel Frank , Blanc Guillermo A , Cao Yixian , Congiu Enrico , Dale Daniel A , Faesi Christopher M , Glover Simon C O , Grasha Kathryn , Groves Brent , Hughes Annie , Klessen Ralf S , Kreckel Kathryn , McElroy Rebecca , Pan Hsi-An , Pety Jérôme , Querejeta Miguel , Razza Alessandro , Rosolowsky Erik , Saito Toshiki , Schinnerer Eva , Sun Jiayi , Tomičić Neven , Usero Antonio , Williams Thomas G 
Published: August 2022

ABSTRACT
The processes of star formation and feedback, regulating the cycle of matter between gas and stars on the scales of giant molecular clouds (GMCs; ∼100 pc), play a major role in governing galaxy evolution. Measuring the time-scales of GMC evolution is important to identify and characterize the specific physical mechanisms that drive this transition. By applying a robust statistical method to high-resolution CO and narrow-band H α imaging from the PHANGS survey, we systematically measure the evolutionary timeline from molecular clouds to exposed young stellar regions on GMC scales, across the discs of an unprecedented sample of 54 star-forming main-sequence galaxies (excluding their unresolved centres). We find that clouds live for about 1−3 GMC turbulence crossing times (5−30 Myr) and are efficiently dispersed by stellar feedback within 1−5 Myr once the star-forming region becomes partially exposed, resulting in integrated star formation efficiencies of 1−8 per cent. These ranges reflect physical galaxy-to-galaxy variation. In order to evaluate whether galactic environment influences GMC evolution, we correlate our measurements with average properties of the GMCs and their local galactic environment. We find several strong correlations that can be physically understood, revealing a quantitative link between galactic-scale environmental properties and the small-scale GMC evolution. Notably, the measured CO-visible cloud lifetimes become shorter with decreasing galaxy mass, mostly due to the increasing presence of CO-dark molecular gas in such environment. Our results represent a first step towards a comprehensive picture of cloud assembly and dispersal, which requires further extension and refinement with tracers of the atomic gas, dust, and deeply embedded stars.
Searching for nascent planetary nebulae: OHPNe candidates in the SPLASH survey
Authors: Cala Roldán A , Gómez José F , Miranda Luis F , Uscanga Lucero , Breen Shari L , Dawson Joanne R , de Gregorio-Monsalvo Itziar , Imai Hiroshi , Qiao Hai-Hua , Suárez Olga 
Published: August 2022

ABSTRACT
The evolution of asymptotic giant branch stars from the spherical symmetry into the diverse shapes of planetary nebulae (PNe) is a topic of intensive research. Young PNe provide a unique opportunity to characterize the onset of this transitional phase. In particular, OH maser-emitting PNe (OHPNe) are considered nascent PNe. In fact, only six OHPNe have been confirmed to date. In order to identify and characterize more OHPNe, we processed the unpublished continuum data of the interferometric follow-up of the Southern Parkes Large-Area Survey in Hydroxyl (SPLASH). We then matched the interferometric positions of OH maser and radio continuum emission, considering the latter as a possible tracer of free–free emission from photoionized gas, characteristic of PNe. We report eight objects with a positive coincidence, four of which are classified as candidate OHPNe here for the first time (IRAS 16372–4808, IRAS 17494–2645, IRAS 18019–2216, and OH 341.6811+00.2634). Available evidence strongly indicates that they are evolved stars, while the comparison with confirmed OHPNe indicates that they are likely to be PNe. Their final confirmation as bona fide PNe, however, requires optical/infrared spectroscopy. The obtained spectral indices of the radio continuum emission (between ≃0.4–1.3) are consistent with partially optically thick free–free emission from photoionized gas. Also, they cluster in the same region of a WISE colour–colour diagram as that of the confirmed OHPNe ($9.5\lesssim[3.4]{-}[22]\lesssim13.5$, and $4.0\lesssim[4.6]{-}[12] \lesssim7.0$), thus this diagram could help to identify more OHPNe candidates in the future.
HIPASS study of southern ultradiffuse galaxies and low surface brightness galaxies
Authors: Zhou Yun-Fan , Sengupta Chandreyee , Chandola Yogesh , Wong O Ivy , Scott Tom C , Ma Yin-Zhe , Chen Hao 
Published: August 2022

ABSTRACT
We present results from an H i counterpart search using the HI Parkes All Sky Survey (HIPASS) for a sample of low surface brightness galaxies (LSBGs) and ultradiffuse galaxies (UDGs) identified from the Dark Energy Survey (DES). We aimed to establish the redshifts of the DES LSBGs to determine the UDG fraction and understand their properties. Out of 409 galaxies investigated, none were unambiguously detected in H i. Our study was significantly hampered by the high spectral rms of HIPASS and thus in this paper we do not make any strong conclusive claims but discuss the main trends and possible scenarios our results reflect. The overwhelming number of non-detections suggest that (a) Either all the LSBGs in the groups, blue or red, have undergone environment aided pre-processing and are H i deficient or the majority of them are distant galaxies, beyond the HIPASS detection threshold. (b) The sample investigated is most likely dominated by galaxies with H i masses typical of dwarf galaxies. Had there been Milky Way (MW) size (Re) galaxies in our sample, with proportionate H i content, they would have been detected, even with the limitations imposed by the HIPASS spectral quality. This leads us to infer that if some of the LSBGs have MW-size optical diameters, their H i content is possibly in the dwarf range. More sensitive observations using the SKA precursors in future may resolve these questions.
Discovering faint and high apparent motion rate near-Earth asteroids using a deep learning program
Authors: Wang Franklin , Ge Jian , Willis Kevin 
Published: August 2022

ABSTRACT
Although many near-Earth objects have been found by ground-based telescopes, some fast-moving ones, especially those near detection limits, have been missed by observatories. We developed a convolutional neural network for detecting faint fast-moving near-Earth objects. It was trained with artificial streaks generated from simulations and was able to find these asteroid streaks with an accuracy of 98.7 per cent and a false positive rate of 0.02 per cent on simulated data. This program was used to search image data from the Zwicky Transient Facility (ZTF) in four nights in 2019, and it identified six previously undiscovered asteroids. The visual magnitudes of our detections range from ∼19.0 to 20.3 and motion rates range from ∼6.8 to 24 deg d−1, which is very faint compared to other ZTF detections moving at similar motion rates. Our asteroids are also ∼1–51 m diameter in size and ∼5–60 lunar distances away at close approach, assuming their albedo values follow the albedo distribution function of known asteroids. The use of a purely simulated data set to train our model enables the program to gain sensitivity in detecting faint and fast-moving objects while still being able to recover nearly all discoveries made by previously designed neural networks which used real detections to train neural networks. Our approach can be adopted by any observatory for detecting fast-moving asteroid streaks.
SDSS-IV MaNGA: the chemical co-evolution of gas and stars in spiral galaxies
Authors: Greener Michael J , Aragón-Salamanca Alfonso , Merrifield Michael , Peterken Thomas , Sazonova Elizaveta , Haggar Roan , Bizyaev Dmitry , Brownstein Joel R , Lane Richard R , Pan Kaike 
Published: August 2022

ABSTRACT
We investigate archaeologically how the metallicity in both stellar and gaseous components of spiral galaxies of differing masses evolve with time, using data from the SDSS-IV MaNGA survey. For the stellar component, we can measure this evolution directly by decomposing the galaxy absorption-line spectra into populations of different ages and determining their metallicities. For the gaseous component, we can only measure the present-day metallicity directly from emission lines. However, there is a well-established relationship between gas metallicity, stellar mass, and star formation rate which does not evolve significantly with redshift; since the latter two quantities can be determined directly for any epoch from the decomposition of the absorption-line spectra, we can use this relationship to infer the variation in gas metallicity over cosmic time. Comparison of present-day values derived in this way with those obtained directly from the emission lines confirms the validity of the method. Application of this approach to a sample of 1619 spiral galaxies reveals how the metallicity of these systems has changed over the last 10 billion yr since cosmic noon. For lower-mass galaxies, both stellar and gaseous metallicity increase together, as one might expect in well-mixed fairly isolated systems. In higher-mass systems, the average stellar metallicity has not increased in step with the inferred gas metallicity, and actually decreases with time. Such disjoint behaviour is what one might expect if these more massive systems have accreted significant amounts of largely pristine gas over their lifetimes, and this material has not been well mixed into the galaxies.
Evolutionary Tuning of Transient Receptor Potential Ankyrin 1 Underlies the Variation in Heat Avoidance Behaviors among Frog Species Inhabiting Diverse Thermal Niches
Authors: Saito Shigeru , Saito Claire T , Igawa Takeshi , Takeda Nodoka , Komaki Shohei , Ohta Toshio , Tominaga Makoto 
Published: August 2022

Abstract
Environmental temperature is a critical factor for all forms of life, and thermal tolerance defines the habitats utilized by a species. Moreover, the evolutionary tuning of thermal perception can also play a key role in habitat selection. Yet, the relative importance of thermal tolerance and perception in environmental adaptation remains poorly understood. Thermal conditions experienced by anuran tadpoles differ among species due to the variation in breeding seasons and water environments selected by parental frogs. In the present study, heat tolerance and avoidance temperatures were compared in tadpoles from five anuran species that spatially and temporally inhabit different thermal niches. These two parameters were positively correlated with each other and were consistent with the thermal conditions of habitats. The species difference in avoidance temperature was 2.6 times larger than that in heat tolerance, suggesting the importance of heat avoidance responses in habitat selection. In addition, the avoidance temperature increased after warm acclimation, especially in the species frequently exposed to heat in their habitats. Characterization of the heat-sensing transient receptor potential ankyrin 1 (TRPA1) ion channel revealed an amphibian-specific alternatively spliced variant containing a single valine insertion relative to the canonical alternative spliced variant of TRPA1, and this novel variant altered the response to thermal stimuli. The two alternatively spliced variants of TRPA1 exhibited different thermal responses in a species-specific manner, which are likely to be associated with a difference in avoidance temperatures among species. Together, our findings suggest that the functional change in TRPA1 plays a crucial role in thermal adaptation processes.