bluuebunny/crossref_metadata_2025_split huggingface dataset:
Surrogate modelling the Baryonic Universe – I. The colour of star formation
Authors: Chaves-Montero Jonás , Hearin Andrew 
Published: May 2020

ABSTRACT
The spectral energy distribution of a galaxy emerges from the complex interplay of many physical ingredients, including its star formation history (SFH), metallicity evolution, and dust properties. Using galaxpy, a new galaxy spectral prediction tool, and SFHs predicted by the empirical model universemachine and the cosmological hydrodynamical simulation IllustrisTNG, we isolate the influence of SFH on optical and near-infrared colours from 320 to 1080 Å at z = 0. By carrying out a principal component analysis, we show that physically motivated SFH variations modify galaxy colours along a single direction in colour space: the SFH-direction. We find that the projection of a galaxy’s present-day colours on to the SFH-direction is almost completely regulated by the fraction of stellar mass that the galaxy formed over the last billion years. Together with cosmic downsizing, this results in galaxies becoming redder as their host halo mass increases. We additionally study the change in galaxy colours due to variations in metallicity, dust attenuation, and nebular emission lines, finding that these properties vary broad-band colours along distinct directions in colour space relative to the SFH-direction. Finally, we show that the colours of low-redshift Sloan Digital Sky Survey galaxies span an ellipsoid with significant extent along two independent dimensions, and that the SFH-direction is well-aligned with the major axis of this ellipsoid. Our analysis supports the conclusion that variations in SFH are the dominant influence on present-day galaxy colours, and that the nature of this influence is strikingly simple.
Possible periodic activity in the repeating FRB 121102
Authors: Rajwade K M , Mickaliger M B , Stappers B W , Morello V , Agarwal D , Bassa C G , Breton R P , Caleb M , Karastergiou A , Keane E F , Lorimer D R 
Published: May 2020

ABSTRACTThe discovery that at least some Fast Radio Bursts (FRBs) repeat has ruled out cataclysmic events as the progenitors of these particular bursts. FRB 121102 is the most well-studied repeating FRB but despite extensive monitoring of the source, no underlying pattern in the repetition has previously been identified. Here, we present the results from a radio monitoring campaign of FRB 121102 using the 76 m Lovell telescope. Using the pulses detected in the Lovell data along with pulses from the literature, we report a detection of periodic behaviour of the source over the span of 5 yr of data. We predict that the source is currently ‘off’ and that it should turn ‘on’ for the approximate MJD range 59002−59089 (2020 June 2 to 2020 August 28). This result, along with the recent detection of periodicity from another repeating FRB, highlights the need for long-term monitoring of repeating FRBs at a high cadence. Using simulations, we show that one needs at least 100 h of telescope time to follow-up repeating FRBs at a cadence of 0.5–3 d to detect periodicities in the range of 10–150 d. If the period is real, it shows that repeating FRBs can have a large range in their activity periods that might be difficult to reconcile with neutron star precession models.
Deprojecting galaxy-cluster cold fronts: evidence for bulk, magnetized spiral flows
Authors: Naor Yossi , Keshet Uri , Wang Qian H S , Reiss Ido 
Published: May 2020

ABSTRACT
Tangential discontinuities known as cold fronts (CFs) are abundant in groups and clusters of galaxies (GCs). The relaxed, spiral-type CFs were initially thought to be isobaric, but a significant, $10{{\ \rm per\ cent}}$–$20{{\ \rm per\ cent}}$ jump in the thermal pressure Pt was reported when deprojected CFs were stacked, interpreted as missing Pt below the CFs (i.e. at smaller radii r) due to a locally enhanced non-thermal pressure Pnt. We report a significant (∼4.3σ) deprojected jump in Pt across a single sharp CF in the Centaurus cluster. Additional seven CFs are deprojected in the GCs A2029, A2142, A2204, and Centaurus, all found to be consistent (stacked: ∼1.9σ) with similar pressure jumps. Combining our sample with high quality deprojected CFs from the literature indicates pressure jumps at significance levels ranging between 2.7σ and 5.0σ, depending on assumptions. Our nominal results are consistent with Pnt ≃ (0.1–0.3)Pt just below the CF. We test different deprojection and analysis methods to confirm that our results are robust, and show that without careful deprojection, an opposite pressure trend may incorrectly be inferred. Analysing all available deprojected data, we also find: (i) small variations around the mean density and temperature CF contrast q within each GC, monotonically increasing with the GC mass M200 as $q\propto M_{200}^{0.23\pm 0.04}$; (ii) hydrostatic mass discontinuities indicating fast bulk tangential flows below all deprojected CFs, with a mean Mach number ∼0.76; and (iii) the newly deprojected CFs are consistent (stacked: ∼2.9σ) with a $1.25^{+0.09}_{-0.08}$ metallicity drop across the CF. These findings suggest that GCs quite generally harbour extended spiral flows.
The impact of spectra quality on nebular abundances
Authors: Rodríguez Mónica 
Published: May 2020

ABSTRACT
I explore the effects of observational errors on nebular chemical abundances using a sample of 179 optical spectra of 42 planetary nebulae (PNe) observed by different authors. The spectra are analysed in a homogeneous way to derive physical conditions and ionic and total abundances. The effects of recombination on the [O ii] and [N ii] emission lines are estimated by including the effective recombination coefficients in the statistical equilibrium equations that are solved for O+ and N+. The results are shown to be significantly different than those derived using previous approaches. The O+ abundances derived with the blue and red lines of [O ii] differ by up to a factor of 6, indicating that the relative intensities of lines widely separated in wavelength can be highly uncertain. In fact, the He ii lines in the range 4000–6800 Å imply that most of the spectra are bluer than expected. Scores are assigned to the spectra using different criteria and the spectrum with the highest score for each PN is taken as the reference spectrum. The differences between the abundances derived with the reference spectrum and those derived with the other spectra available for each object are used to estimate the 1σ observational uncertainties in the final abundances: 0.11 dex for O/H and Ar/H, 0.14 dex for N/H, Ne/H, and Cl/H, and 0.16 dex for S/H.
SDSS-IV MaNGA: spatially resolved dust attenuation in spiral galaxies
Authors: Greener Michael J , Aragón-Salamanca Alfonso , Merrifield Michael R , Peterken Thomas G , Fraser-McKelvie Amelia , Masters Karen L , Krawczyk Coleman M , Boardman Nicholas F , Boquien Médéric , Andrews Brett H , Brinkmann Jonathan , Drory Niv 
Published: May 2020

ABSTRACT
Dust attenuation in star-forming spiral galaxies affects stars and gas in different ways due to local variations in dust geometry. We present spatially resolved measurements of dust attenuation for a sample of 232 such star-forming spiral galaxies, derived from spectra acquired by the SDSS-IV MaNGA survey. The dust attenuation affecting the stellar populations of these galaxies (obtained using full spectrum stellar population fitting methods) is compared with the dust attenuation in the gas (derived from the Balmer decrement). Both of these attenuation measures increase for local regions of galaxies with higher star formation rates; the dust attenuation affecting the stellar populations increases more so than the dust attenuation in the gas, causing the ratio of the dust attenuation affecting the stellar populations to the dust attenuation in the gas to decrease for local regions of galaxies with higher star formation rate densities. No systematic difference is discernible in any of these dust attenuation quantities between the spiral arm and interarm regions of the galaxies. While both the dust attenuation in the gas and the dust attenuation affecting the stellar populations decrease with galactocentric radius, the ratio of the two quantities does not vary with radius. This ratio does, however, decrease systematically as the stellar mass of the galaxy increases. Analysis of the radial profiles of the two dust attenuation measures suggests that there is a disproportionately high concentration of birth clouds (incorporating gas, young stars, and clumpy dust) nearer to the centres of star-forming spiral galaxies.
See Change: VLT spectroscopy of a sample of high-redshift Type Ia supernova host galaxies
Authors: Williams S C , Hook I M , Hayden B , Nordin J , Aldering G , Boone K , Goobar A , Lidman C E , Perlmutter S , Rubin D , Ruiz-Lapuente P , Saunders C ,   (The Supernova Cosmology Project)
Published: May 2020

ABSTRACT
The Supernova Cosmology Project has conducted the ‘See Change’ programme, aimed at discovering and observing high-redshift (1.13 ≤ z ≤ 1.75) Type Ia supernovae (SNe Ia). We used multifilter Hubble Space Telescope (HST) observations of massive galaxy clusters with sufficient cadence to make the observed SN Ia light curves suitable for a cosmological probe of dark energy at z &gt; 0.5. This See Change sample of SNe Ia with multi-colour light curves will be the largest to date at these redshifts. As part of the See Change programme, we obtained ground-based spectroscopy of each discovered transient and/or its host galaxy. Here, we present Very Large Telescope (VLT) spectra of See Change transient host galaxies, deriving their redshifts, and host parameters such as stellar mass and star formation rate. Of the 39 See Change transients/hosts that were observed with the VLT, we successfully determined the redshift for 26, including 15 SNe Ia at z &gt; 0.97. We show that even in passive environments, it is possible to recover secure redshifts for the majority of SN hosts out to z = 1.5. We find that with typical exposure times of 3−4 h on an 8-m-class telescope we can recover ∼75 per cent of SN Ia redshifts in the range of 0.97 &lt; z &lt; 1.5. Furthermore, we show that the combination of HST photometry and VLT spectroscopy is able to provide estimates of host galaxy stellar mass that are sufficiently accurate for use in a mass-step correction in the cosmological analysis.
Accretion disc–jet couplings in X-ray binaries
Authors: Shen Pei-Xin , Gu Wei-Min 
Published: May 2020

ABSTRACT
When the matter from a companion star is accreted towards the central compact accretor, i.e. a black hole (BH) or a neutron star (NS), an accretion disc and a jet outflow will form, providing bight X-ray and radio emission, which is known as X-ray binaries (XRBs). In the low/hard state, there exist disc–jet couplings in XRBs, but it remains uncertain whether the jet power comes from the disc or the central accretor. Moreover, black hole X-ray binaries (BHXRBs) have different properties compared with neutron star X-ray binaries (NSXRBs): quiescent BHXRBs are typically two to three orders of magnitude less luminous than NSXRBs in X-ray, whereas BHXRBs are more radio loud than NSXRBs. In observations, an empirical correlation has been established between radio and X-ray luminosity, $L_{\rm R} \propto L_{\rm X}^b$, where b ∼ 0.7 for BHXRBs and b ∼ 1.4 for non-pulsating NSXRBs. However, there are some outliers of BHXRBs showing unusually steep correlation as NSXRBs at higher luminosities. In this work, under the assumption that the origin of jet power is related to the internal energy of the inner disc, we apply our magnetized, radiatively efficient thin disc model and the well-known radiatively inefficient accretion flow model to NSXRBs and BHXRBs. We find that the observed radio/X-ray correlations in XRBs can be well understood by the disc–jet couplings.
Separating the intrinsic alignment signal and the lensing signal using self-calibration in photo-z surveys with KiDS450 and KV450 Data
Authors: Yao Ji , Pedersen Eske M , Ishak Mustapha , Zhang Pengjie , Agashe Anish , Xu Haojie , Shan Huanyuan 
Published: May 2020

ABSTRACT
To reach the full potential for the next generation of weak lensing surveys, it is necessary to mitigate the contamination of intrinsic alignments (IAs) of galaxies in the observed cosmic shear signal. The self-calibration (SC) of IAs provides an independent method to measure the IA signal from the survey data and the photometric redshift information. It operates differently from the marginalization method based on the IA modelling. In this work, we present the first application of SC to the KiDS450 data and the KV450 data, to split directly the intrinsic shape–galaxy density (Ig) correlation signal and the gravitational shear–galaxy density (Gg) correlation signal, using the information from photometric redshift (photo-z). We achieved a clear separation of the two signals and performed several validation tests. Our measured signals are found to be in general agreement with the KiDS450 cosmic shear best-fitting cosmology, for both lensing and IA measurements. For KV450, we use partial (high-z) data, and our lensing measurements are also in good agreement with KV450 cosmic shear best fit, while our IA signal suggests a larger IA amplitude for the high-z sample. We discussed the impact of photo-z quality on IA detection and several other potential systematic biases. Finally, we discuss the potential application of the information extracted for both the lensing signal and the IA signal in future surveys.
Asymmetric surface brightness structure of caustic crossing arc in SDSS J1226+2152: a case for dark matter substructure
Authors: Dai Liang , Kaurov Alexander A , Sharon Keren , Florian Michael , Miralda-Escudé Jordi , Venumadhav Tejaswi , Frye Brenda , Rigby Jane R , Bayliss Matthew 
Published: May 2020

ABSTRACT
We study the highly magnified arc SGAS J122651.3+215220 caused by a star-forming galaxy at zs = 2.93 crossing the lensing caustic cast by the galaxy cluster SDSS J1226+2152 (zl = 0.43), using Hubble Space Telescope observations. We report in the arc several asymmetric surface brightness features whose angular separations are a fraction of an arcsecond from the lensing critical curve and appear to be highly but unequally magnified image pairs of underlying compact sources, with one brightest pair having clear asymmetry consistently across four filters. One explanation of unequal magnification is microlensing by intracluster stars, which induces independent flux variations in the images of individual or groups of source stars in the lensed galaxy. For a second possibility, intracluster dark matter subhaloes invisible to telescopes effectively perturb lensing magnifications near the critical curve and give rise to persistently unequal image pairs. Our modelling suggests, at least for the most prominent identified image pair, that the microlensing hypothesis is in tension with the absence of notable asymmetry variation over a six-year baseline, while subhaloes of ∼106–$10^8\, \mathrm{ M}_\odot$ anticipated from structure formation with cold dark matter typically produce stationary and sizable asymmetries. We judge that observations at additional times and more precise lens models are necessary to stringently constrain temporal variability and robustly distinguish between the two explanations. The arc under this study is a scheduled target of a Director’s Discretionary Early Release Science program of the James Webb Space Telescope, which will provide deep images and a high-resolution view with integral field spectroscopy.
A catalogue of open cluster radii determined from Gaia proper motions
Authors: Sánchez Néstor , Alfaro Emilio J , López-Martínez Fátima 
Published: May 2020

ABSTRACT
In this work, we improve a previously published method to calculate in a reliable way the radius of an open cluster (OC). The method is based on the behaviour of stars in the proper motion space as the sampling changes in the position space. Here, we describe the new version of the method and show its performance and robustness. Additionally, we apply it to a large number of OCs using data from Gaia second data release to generate a catalogue of 401 clusters with reliable radius estimations. The range of obtained apparent radii goes from Rc = 1.4 ± 0.1 arcmin (for the cluster FSR 1651) to Rc = 25.5 ± 3.5 arcmin (for NGC 2437). Cluster linear sizes follow very closely a lognormal distribution with a mean characteristic radius of Rc = 3.7 pc, and its high radius tail can be fitted by a power law as $N \propto R_c^{-3.11\pm 0.35}$. Additionally, we find that number of members, cluster radius, and age follow the relationship $N_c \propto R_c^{1.2\pm 0.1} \cdot T_c^{-1.9\pm 0.4}$ where the younger and more extensive the cluster, the more members it presents. The proposed method is not sensitive to low density or irregular spatial distributions of stars and, therefore, is a good alternative or complementary procedure to calculate OC radii not having previous information on star memberships.
snapshot: connections between internal and surface properties of massive stars
Authors: Farrell Eoin J , Groh Jose H , Meynet Georges , Eldridge J J , Ekström Sylvia , Georgy Cyril 
Published: May 2020

ABSTRACT
We introduce snapshot, a technique to systematically compute stellar structure models in hydrostatic and thermal equilibrium based on three structural properties – core mass Mcore, envelope mass Menv, and core composition. This approach allows us to connect these properties of stellar interiors to the luminosity and effective temperature Teff in a more systematic way than with stellar evolution models. We compute core-H burning models with total masses of Mtotal = 8–60 M⊙ and central H mass fractions from 0.70 to 0.05. Using these, we derive an analytical relationship between Mcore, Mtotal, and central H abundance that can be readily used in rapid stellar evolution algorithms. In contrast, core-He burning stars can have a wide range of combinations of Mcore, Menv, and core compositions. We compute core-He burning models with Mcore = 2–9 M⊙, Menv = 0–50 M⊙, and central He mass fractions of 0.50 and 0.01. Models with Mcore/Mtotal from 0.2 to 0.8 have convective envelopes, low Teff and will appear as red supergiants (RSGs). For a given Mcore, they exhibit a small variation in luminosity (0.02 dex) and Teff ($\sim 400\, \mathrm{K}$) over a wide range of Menv ($\sim$2–20 M⊙). This means that it is not possible to derive RSG masses from luminosities and Teff alone. We derive the following relationship between Mcore and the total luminosity of an RSG during core He burning: log Mcore ≃ 0.44log L/L⊙ − 1.38. At Mcore/Mtotal ≈ 0.2, our models exhibit a bistability and jump from an RSG to a BSG structure. Our models with Mcore/Mtotal &gt; 0.8, which correspond to stripped stars produced by mass-loss or binary interaction, show that Teff has a strong dependence on Menv, Mcore, and the core composition. We constrain the mass of one of these stripped stars in a binary system, HD 45166, and find it to be less than its estimated dynamical mass. When a large observational sample of stripped stars becomes available, our results can be used to constrain their Mcore, Menv, mass-loss rates, and the physics of binary interaction.
frankenstein: protoplanetary disc brightness profile reconstruction at sub-beam resolution with a rapid Gaussian process
Authors: Jennings Jeff , Booth Richard A , Tazzari Marco , Rosotti Giovanni P , Clarke Cathie J 
Published: May 2020

ABSTRACT
Interferometric observations of the mm dust distribution in protoplanetary discs are now showing a ubiquity of annular gap and ring substructures. Their identification and accurate characterization are critical to probing the physical processes responsible. We present frankenstein (frank), an open source code that recovers axisymmetric disc structures at a sub-beam resolution. By fitting the visibilities directly, the model reconstructs a disc’s 1D radial brightness profile non-parametrically using a fast (≲1 min) Gaussian process. The code avoids limitations of current methods that obtain the radial brightness profile either by extracting it from the disc image via non-linear deconvolution at the cost of reduced fit resolution or by assumptions placed on the functional forms of disc structures to fit the visibilities parametrically. We use mock Atacama Large Millimeter Array observations to quantify the method’s intrinsic capability and its performance as a function of baseline-dependent signal-to-noise ratio. Comparing the technique to profile extraction from a clean image, we motivate how our fits accurately recover disc structures at a sub-beam resolution. Demonstrating the model’s utility in fitting real high- and moderate-resolution observations, we conclude by proposing applications to address open questions on protoplanetary disc structure and processes.
Thermally driven disc winds as a mechanism for X-ray irradiation heating in black hole X-ray binaries: the case study of GX339–4
Authors: Tetarenko B E , Dubus G , Marcel G , Done C , Clavel M 
Published: May 2020

ABSTRACT
X-ray irradiation heating of accretion discs in black hole X-ray binaries (BHXBs) plays a key role in regulating their outburst cycles. However, despite decades of theoretical and observational efforts, the physical mechanism(s) responsible for irradiating these discs remains largely unknown. We have built an observation-based methodology to estimate the strength of irradiation of BHXB discs by combining multiwavelength X-ray and optical/infrared (OIR) data throughout transient outbursts. We apply this to ∼15 yr of activity in the Galactic BHXB GX339–4. Our findings suggest that the irradiation heating required by the optical data is large in this system. Direct illumination of the outer disc does not produce sufficient irradiation, but this should also produce a thermal-radiative wind which adds to the irradiation heating by scattering flux down on to the disc. However, analytic estimates of X-ray illumination from scattering in the wind are still not sufficient to produce the observed heating, even in combination with direct illumination. Either the analytic thermal-radiative wind models are underestimating the effect of the wind, or there are additional scattering mechanisms at work, such as magnetically driven outflows, acting to increase the OIR flux. While wind-driven irradiation is likely a common feature among long-period BHXBs, fully understanding the driving mechanism(s) behind such a wind will require radiation hydrodynamic simulations.