@article{11516, abstract = {The well-known quasar SDSS J095253.83+011421.9 (J0952+0114) at z = 3.02 has one of the most peculiar spectra discovered so far, showing the presence of narrow Lyα and broad metal emission lines. Although recent studies have suggested that a proximate damped Lyα absorption (PDLA) system causes this peculiar spectrum, the origin of the gas associated with the PDLA is unknown. Here we report the results of observations with the Multi Unit Spectroscopic Explorer (MUSE) that reveal a new giant (≈100 physical kpc) Lyα nebula. The detailed analysis of the Lyα velocity, velocity dispersion, and surface brightness profiles suggests that the J0952+0114 Lyα nebula shares similar properties with other QSO nebulae previously detected with MUSE, implying that the PDLA in J0952+0144 is covering only a small fraction of the solid angle of the QSO emission. We also detected bright and spectrally narrow C iv λ1550 and He ii λ1640 extended emission around J0952+0114 with velocity centroids similar to the peak of the extended and central narrow Lyα emission. The presence of a peculiarly bright, unresolved, and relatively broad He ii λ1640 emission in the central region at exactly the same PDLA redshift hints at the possibility that the PDLA originates in a clumpy outflow with a bulk velocity of about 500 km s−1. The smaller velocity dispersion of the large-scale Lyα emission suggests that the high-speed outflow is confined to the central region. Lastly, the derived spatially resolved He ii/Lyα and C iv/Lyα maps show a positive gradient with the distance to the QSO, hinting at a non-homogeneous distribution of the ionization parameter.}, author = {Marino, Raffaella Anna and Cantalupo, Sebastiano and Pezzulli, Gabriele and Lilly, Simon J. and Gallego, Sofia and Mackenzie, Ruari and Matthee, Jorryt J and Brinchmann, Jarle and Bouché, Nicolas and Feltre, Anna and Muzahid, Sowgat and Schroetter, Ilane and Johnson, Sean D. and Nanayakkara, Themiya}, issn = {1538-4357}, journal = {The Astrophysical Journal}, keywords = {Space and Planetary Science, Astronomy and Astrophysics}, number = {1}, publisher = {IOP Publishing}, title = {{A giant Lyα nebula and a small-scale clumpy outflow in the system of the exotic quasar J0952+0114 unveiled by MUSE}}, doi = {10.3847/1538-4357/ab2881}, volume = {880}, year = {2019}, } @article{11515, abstract = {We present new deep ALMA and Hubble Space Telescope (HST)/WFC3 observations of MASOSA and VR7, two luminous Lyα emitters (LAEs) at z = 6.5, for which the UV continuum levels differ by a factor of four. No IR dust continuum emission is detected in either, indicating little amounts of obscured star formation and/or high dust temperatures. MASOSA, with a UV luminosity M1500 = −20.9, compact size, and very high Lyα ${\mathrm{EW}}_{0}\approx 145\,\mathring{\rm A} $, is undetected in [C ii] to a limit of L[C ii] < 2.2 × 107 L⊙, implying a metallicity Z ≲ 0.07 Z⊙. Intriguingly, our HST data indicate a red UV slope β = −1.1 ± 0.7, at odds with the low dust content. VR7, which is a bright (M1500 = −22.4) galaxy with moderate color (β = −1.4 ± 0.3) and Lyα EW0 = 34 Å, is clearly detected in [C ii] emission (S/N = 15). VR7's rest-frame UV morphology can be described by two components separated by ≈1.5 kpc and is globally more compact than the [C ii] emission. The global [C ii]/UV ratio indicates Z ≈ 0.2 Z⊙, but there are large variations in the UV/[C ii] ratio on kiloparsec scales. We also identify diffuse, possibly outflowing, [C ii]-emitting gas at ≈100 km s−1 with respect to the peak. VR7 appears to be assembling its components at a slightly more evolved stage than other luminous LAEs, with outflows already shaping its direct environment at z ∼ 7. Our results further indicate that the global [C ii]−UV relation steepens at SFR < 30 M⊙ yr−1, naturally explaining why the [C ii]/UV ratio is anticorrelated with Lyα EW in many, but not all, observed LAEs.}, author = {Matthee, Jorryt J and Sobral, D. and Boogaard, L. A. and Röttgering, H. and Vallini, L. and Ferrara, A. and Paulino-Afonso, A. and Boone, F. and Schaerer, D. and Mobasher, B.}, issn = {1538-4357}, journal = {The Astrophysical Journal}, keywords = {Space and Planetary Science, Astronomy and Astrophysics}, number = {2}, publisher = {IOP Publishing}, title = {{Resolved UV and [C ii] structures of luminous galaxies within the epoch of reionization}}, doi = {10.3847/1538-4357/ab2f81}, volume = {881}, year = {2019}, } @article{11517, abstract = {To understand star formation in galaxies, we investigate the star formation rate (SFR) surface density (ΣSFR) profiles for galaxies, based on a well-defined sample of 976 star-forming MaNGA galaxies. We find that the typical ΣSFR profiles within 1.5Re of normal SF galaxies can be well described by an exponential function for different stellar mass intervals, while the sSFR profile shows positive gradients, especially for more massive SF galaxies. This is due to the more pronounced central cores or bulges rather than the onset of a `quenching' process. While galaxies that lie significantly above (or below) the star formation main sequence (SFMS) show overall an elevation (or suppression) of ΣSFR at all radii, this central elevation (or suppression) is more pronounced in more massive galaxies. The degree of central enhancement and suppression is quite symmetric, suggesting that both the elevation and suppression of star formation are following the same physical processes. Furthermore, we find that the dispersion in ΣSFR within and across the population is found to be tightly correlated with the inferred gas depletion time, whether based on the stellar surface mass density or the orbital dynamical time. This suggests that we are seeing the response of a simple gas-regulator system to variations in the accretion rate. This is explored using a heuristic model that can quantitatively explain the dependence of σ(ΣSFR) on gas depletion timescale. Variations in accretion rate are progressively more damped out in regions of low star-formation efficiency leading to a reduced amplitude of variations in star-formation.}, author = {Wang, Enci and Lilly, Simon J. and Pezzulli, Gabriele and Matthee, Jorryt J}, issn = {1538-4357}, journal = {The Astrophysical Journal}, keywords = {Space and Planetary Science, Astronomy and Astrophysics}, number = {2}, publisher = {IOP Publishing}, title = {{On the elevation and suppression of star formation within galaxies}}, doi = {10.3847/1538-4357/ab1c5b}, volume = {877}, year = {2019}, } @article{11535, abstract = {We investigate the clustering and halo properties of ∼5000 Ly α-selected emission-line galaxies (LAEs) from the Slicing COSMOS 4K (SC4K) and from archival NB497 imaging of SA22 split in 15 discrete redshift slices between z ∼ 2.5 and 6. We measure clustering lengths of r0 ∼ 3–6 h−1 Mpc and typical halo masses of ∼1011 M⊙ for our narrowband-selected LAEs with typical LLy α ∼ 1042–43 erg s−1. The intermediate-band-selected LAEs are observed to have r0 ∼ 3.5–15 h−1 Mpc with typical halo masses of ∼1011–12 M⊙ and typical LLy α ∼ 1043–43.6 erg s−1. We find a strong, redshift-independent correlation between halo mass and Ly α luminosity normalized by the characteristic Ly α luminosity, L⋆(z). The faintest LAEs (L ∼ 0.1 L⋆(z)) typically identified by deep narrowband surveys are found in 1010 M⊙ haloes and the brightest LAEs (L ∼ 7 L⋆(z)) are found in ∼5 × 1012 M⊙ haloes. A dependency on the rest-frame 1500 Å UV luminosity, MUV, is also observed where the halo masses increase from 1011 to 1013 M⊙ for MUV ∼ −19 to −23.5 mag. Halo mass is also observed to increase from 109.8 to 1012 M⊙ for dust-corrected UV star formation rates from ∼0.6 to 10 M⊙ yr−1 and continues to increase up to 1013 M⊙ in halo mass, where the majority of those sources are active galactic nuclei. All the trends we observe are found to be redshift independent. Our results reveal that LAEs are the likely progenitors of a wide range of galaxies depending on their luminosity, from dwarf-like, to Milky Way-type, to bright cluster galaxies. LAEs therefore provide unique insight into the early formation and evolution of the galaxies we observe in the local Universe.}, author = {Khostovan, A A and Sobral, D and Mobasher, B and Matthee, Jorryt J and Cochrane, R K and Chartab, N and Jafariyazani, M and Paulino-Afonso, A and Santos, S and Calhau, J}, issn = {1365-2966}, journal = {Monthly Notices of the Royal Astronomical Society}, keywords = {Space and Planetary Science, Astronomy and Astrophysics, galaxies: evolution, galaxies: haloes, galaxies: high-redshift, galaxies: star formation, cosmology: observations, large-scale structure of Universe}, number = {1}, pages = {555--573}, publisher = {Oxford University Press}, title = {{The clustering of typical Ly α emitters from z ∼ 2.5–6: Host halo masses depend on Ly α and UV luminosities}}, doi = {10.1093/mnras/stz2149}, volume = {489}, year = {2019}, } @article{11541, abstract = {We present new Hubble Space Telescope (HST)/WFC3 observations and re-analyse VLT data to unveil the continuum, variability, and rest-frame ultraviolet (UV) lines of the multiple UV clumps of the most luminous Lyα emitter at z = 6.6, CR7 (COSMOS Redshift 7). Our re-reduced, flux-calibrated X-SHOOTER spectra of CR7 reveal an He II emission line in observations obtained along the major axis of Lyα emission with the best seeing conditions. He II is spatially offset by ≈+0.8 arcsec from the peak of Lyα emission, and it is found towards clump B. Our WFC3 grism spectra detects the UV continuum of CR7’s clump A, yielding a power law with β=−2.5+0.6−0.7 and MUV=−21.87+0.25−0.20⁠. No significant variability is found for any of the UV clumps on their own, but there is tentative (≈2.2 σ) brightening of CR7 in F110W as a whole from 2012 to 2017. HST grism data fail to robustly detect rest-frame UV lines in any of the clumps, implying fluxes ≲2×10−17 erg s−1 cm−2 (3σ). We perform CLOUDY modelling to constrain the metallicity and the ionizing nature of CR7. CR7 seems to be actively forming stars without any clear active galactic nucleus activity in clump A, consistent with a metallicity of ∼0.05–0.2 Z⊙. Component C or an interclump component between B and C may host a high ionization source. Our results highlight the need for spatially resolved information to study the formation and assembly of early galaxies.}, author = {Sobral, David and Matthee, Jorryt J and Brammer, Gabriel and Ferrara, Andrea and Alegre, Lara and Röttgering, Huub and Schaerer, Daniel and Mobasher, Bahram and Darvish, Behnam}, issn = {1365-2966}, journal = {Monthly Notices of the Royal Astronomical Society}, keywords = {Space and Planetary Science, Astronomy and Astrophysics, galaxies: evolution, galaxies: high-redshift, galaxies: ISM, cosmology: observations, dark ages, reionization, first stars, early Universe}, number = {2}, pages = {2422--2441}, publisher = {Oxford University Press}, title = {{On the nature and physical conditions of the luminous Ly α emitter CR7 and its rest-frame UV components}}, doi = {10.1093/mnras/sty2779}, volume = {482}, year = {2019}, } @article{11540, abstract = {Observations have revealed that the star formation rate (SFR) and stellar mass (Mstar) of star-forming galaxies follow a tight relation known as the galaxy main sequence. However, what physical information is encoded in this relation is under debate. Here, we use the EAGLE cosmological hydrodynamical simulation to study the mass dependence, evolution, and origin of scatter in the SFR–Mstar relation. At z = 0, we find that the scatter decreases slightly with stellar mass from 0.35 dex at Mstar ≈ 109 M⊙ to 0.30 dex at Mstar ≳ 1010.5 M⊙. The scatter decreases from z = 0 to z = 5 by 0.05 dex at Mstar ≳ 1010 M⊙ and by 0.15 dex for lower masses. We show that the scatter at z = 0.1 originates from a combination of fluctuations on short time-scales (ranging from 0.2–2 Gyr) that are presumably associated with self-regulation from cooling, star formation, and outflows, but is dominated by long time-scale (∼10 Gyr) variations related to differences in halo formation times. Shorter time-scale fluctuations are relatively more important for lower mass galaxies. At high masses, differences in black hole formation efficiency cause additional scatter, but also diminish the scatter caused by different halo formation times. While individual galaxies cross the main sequence multiple times during their evolution, they fluctuate around tracks associated with their halo properties, i.e. galaxies above/below the main sequence at z = 0.1 tend to have been above/below the main sequence for ≫1 Gyr.}, author = {Matthee, Jorryt J and Schaye, Joop}, issn = {1365-2966}, journal = {Monthly Notices of the Royal Astronomical Society}, keywords = {Space and Planetary Science, Astronomy and Astrophysics : galaxies: evolution, galaxies: formation, galaxies: star formation, cosmology: theory}, number = {1}, pages = {915--932}, publisher = {Oxford University Press}, title = {{The origin of scatter in the star formation rate–stellar mass relation}}, doi = {10.1093/mnras/stz030}, volume = {484}, year = {2019}, } @article{11616, abstract = {We present the discovery of HD 221416 b, the first transiting planet identified by the Transiting Exoplanet Survey Satellite (TESS) for which asteroseismology of the host star is possible. HD 221416 b (HIP 116158, TOI-197) is a bright (V = 8.2 mag), spectroscopically classified subgiant that oscillates with an average frequency of about 430 μHz and displays a clear signature of mixed modes. The oscillation amplitude confirms that the redder TESS bandpass compared to Kepler has a small effect on the oscillations, supporting the expected yield of thousands of solar-like oscillators with TESS 2 minute cadence observations. Asteroseismic modeling yields a robust determination of the host star radius (R⋆ = 2.943 ± 0.064 R⊙), mass (M⋆ = 1.212 ± 0.074 M⊙), and age (4.9 ± 1.1 Gyr), and demonstrates that it has just started ascending the red-giant branch. Combining asteroseismology with transit modeling and radial-velocity observations, we show that the planet is a "hot Saturn" (Rp = 9.17 ± 0.33 R⊕) with an orbital period of ∼14.3 days, irradiance of F = 343 ± 24 F⊕, and moderate mass (Mp = 60.5 ± 5.7 M⊕) and density (ρp = 0.431 ± 0.062 g cm−3). The properties of HD 221416 b show that the host-star metallicity–planet mass correlation found in sub-Saturns (4–8 R⊕) does not extend to larger radii, indicating that planets in the transition between sub-Saturns and Jupiters follow a relatively narrow range of densities. With a density measured to ∼15%, HD 221416 b is one of the best characterized Saturn-size planets to date, augmenting the small number of known transiting planets around evolved stars and demonstrating the power of TESS to characterize exoplanets and their host stars using asteroseismology.}, author = {Huber, Daniel and Chaplin, William J. and Chontos, Ashley and Kjeldsen, Hans and Christensen-Dalsgaard, Jørgen and Bedding, Timothy R. and Ball, Warrick and Brahm, Rafael and Espinoza, Nestor and Henning, Thomas and Jordán, Andrés and Sarkis, Paula and Knudstrup, Emil and Albrecht, Simon and Grundahl, Frank and Andersen, Mads Fredslund and Pallé, Pere L. and Crossfield, Ian and Fulton, Benjamin and Howard, Andrew W. and Isaacson, Howard T. and Weiss, Lauren M. and Handberg, Rasmus and Lund, Mikkel N. and Serenelli, Aldo M. and Rørsted Mosumgaard, Jakob and Stokholm, Amalie and Bieryla, Allyson and Buchhave, Lars A. and Latham, David W. and Quinn, Samuel N. and Gaidos, Eric and Hirano, Teruyuki and Ricker, George R. and Vanderspek, Roland K. and Seager, Sara and Jenkins, Jon M. and Winn, Joshua N. and Antia, H. M. and Appourchaux, Thierry and Basu, Sarbani and Bell, Keaton J. and Benomar, Othman and Bonanno, Alfio and Buzasi, Derek L. and Campante, Tiago L. and Çelik Orhan, Z. and Corsaro, Enrico and Cunha, Margarida S. and Davies, Guy R. and Deheuvels, Sebastien and Grunblatt, Samuel K. and Hasanzadeh, Amir and Di Mauro, Maria Pia and A. García, Rafael and Gaulme, Patrick and Girardi, Léo and Guzik, Joyce A. and Hon, Marc and Jiang, Chen and Kallinger, Thomas and Kawaler, Steven D. and Kuszlewicz, James S. and Lebreton, Yveline and Li, Tanda and Lucas, Miles and Lundkvist, Mia S. and Mann, Andrew W. and Mathis, Stéphane and Mathur, Savita and Mazumdar, Anwesh and Metcalfe, Travis S. and Miglio, Andrea and F. G. Monteiro, Mário J. P. and Mosser, Benoit and Noll, Anthony and Nsamba, Benard and Joel Ong, Jia Mian and Örtel, S. and Pereira, Filipe and Ranadive, Pritesh and Régulo, Clara and Rodrigues, Thaíse S. and Roxburgh, Ian W. and Aguirre, Victor Silva and Smalley, Barry and Schofield, Mathew and Sousa, Sérgio G. and Stassun, Keivan G. and Stello, Dennis and Tayar, Jamie and White, Timothy R. and Verma, Kuldeep and Vrard, Mathieu and Yıldız, M. and Baker, David and Bazot, Michaël and Beichmann, Charles and Bergmann, Christoph and Bugnet, Lisa Annabelle and Cale, Bryson and Carlino, Roberto and Cartwright, Scott M. and Christiansen, Jessie L. and Ciardi, David R. and Creevey, Orlagh and Dittmann, Jason A. and Nascimento, Jose-Dias Do and Eylen, Vincent Van and Fürész, Gabor and Gagné, Jonathan and Gao, Peter and Gazeas, Kosmas and Giddens, Frank and Hall, Oliver J. and Hekker, Saskia and Ireland, Michael J. and Latouf, Natasha and LeBrun, Danny and Levine, Alan M. and Matzko, William and Natinsky, Eva and Page, Emma and Plavchan, Peter and Mansouri-Samani, Masoud and McCauliff, Sean and Mullally, Susan E. and Orenstein, Brendan and Soto, Aylin Garcia and Paegert, Martin and van Saders, Jennifer L. and Schnaible, Chloe and Soderblom, David R. and Szabó, Róbert and Tanner, Angelle and Tinney, C. G. and Teske, Johanna and Thomas, Alexandra and Trampedach, Regner and Wright, Duncan and Yuan, Thomas T. and Zohrabi, Farzaneh}, issn = {0004-6256}, journal = {The Astronomical Journal}, keywords = {Space and Planetary Science, Astronomy and Astrophysics}, number = {6}, publisher = {IOP Publishing}, title = {{A hot Saturn orbiting an oscillating late subgiant discovered by TESS}}, doi = {10.3847/1538-3881/ab1488}, volume = {157}, year = {2019}, } @article{11613, abstract = {Over 2,000 stars were observed for 1 month with a high enough cadence in order to look for acoustic modes during the survey phase of the Kepler mission. Solar-like oscillations have been detected in about 540 stars. The question of why no oscillations were detected in the remaining stars is still open. Previous works explained the non-detection of modes with the high level of magnetic activity of the stars. However, the sample of stars studied contained some classical pulsators and red giants that could have biased the results. In this work, we revisit this analysis on a cleaner sample of main-sequence solar-like stars that consists of 1,014 stars. First we compute the predicted amplitude of the modes of that sample and for the stars with detected oscillation and compare it to the noise at high frequency in the power spectrum. We find that the stars with detected modes have an amplitude to noise ratio larger than 0.94. We measure reliable rotation periods and the associated photometric magnetic index for 684 stars out of the full sample and in particular for 323 stars where the amplitude of the modes is predicted to be high enough to be detected. We find that among these 323 stars 32% of them have a level of magnetic activity larger than the Sun during its maximum activity, explaining the non-detection of acoustic modes. Interestingly, magnetic activity cannot be the primary reason responsible for the absence of detectable modes in the remaining 68% of the stars without acoustic modes detected and with reliable rotation periods. Thus, we investigate metallicity, inclination angle of the rotation axis, and binarity as possible causes of low mode amplitudes. Using spectroscopic observations for a subsample, we find that a low metallicity could be the reason for suppressed modes. No clear correlation with binarity nor inclination is found. We also derive the lower limit for our photometric activity index (of 20–30 ppm) below which rotation and magnetic activity are not detected. Finally, with our analysis we conclude that stars with a photometric activity index larger than 2,000 ppm have 98.3% probability of not having oscillations detected.}, author = {Mathur, Savita and García, Rafael A. and Bugnet, Lisa Annabelle and Santos, Ângela R.G. and Santiago, Netsha and Beck, Paul G.}, issn = {2296-987X}, journal = {Frontiers in Astronomy and Space Sciences}, keywords = {Astronomy and Astrophysics}, publisher = {Frontiers Media}, title = {{Revisiting the impact of stellar magnetic activity on the detectability of solar-like oscillations by Kepler}}, doi = {10.3389/fspas.2019.00046}, volume = {6}, year = {2019}, } @article{11615, abstract = {The recently published Kepler mission Data Release 25 (DR25) reported on ∼197 000 targets observed during the mission. Despite this, no wide search for red giants showing solar-like oscillations have been made across all stars observed in Kepler’s long-cadence mode. In this work, we perform this task using custom apertures on the Kepler pixel files and detect oscillations in 21 914 stars, representing the largest sample of solar-like oscillating stars to date. We measure their frequency at maximum power, νmax, down to νmax≃4μHz and obtain log (g) estimates with a typical uncertainty below 0.05 dex, which is superior to typical measurements from spectroscopy. Additionally, the νmax distribution of our detections show good agreement with results from a simulated model of the Milky Way, with a ratio of observed to predicted stars of 0.992 for stars with 10<νmax<270μHz. Among our red giant detections, we find 909 to be dwarf/subgiant stars whose flux signal is polluted by a neighbouring giant as a result of using larger photometric apertures than those used by the NASA Kepler science processing pipeline. We further find that only 293 of the polluting giants are known Kepler targets. The remainder comprises over 600 newly identified oscillating red giants, with many expected to belong to the Galactic halo, serendipitously falling within the Kepler pixel files of targeted stars.}, author = {Hon, Marc and Stello, Dennis and García, Rafael A and Mathur, Savita and Sharma, Sanjib and Colman, Isabel L and Bugnet, Lisa Annabelle}, issn = {1365-2966}, journal = {Monthly Notices of the Royal Astronomical Society}, keywords = {Space and Planetary Science, Astronomy and Astrophysics, asteroseismology, methods: data analysis, techniques: image processing, stars: oscillations, stars: statistics}, number = {4}, pages = {5616--5630}, publisher = {Oxford University Press}, title = {{A search for red giant solar-like oscillations in all Kepler data}}, doi = {10.1093/mnras/stz622}, volume = {485}, year = {2019}, } @article{11614, abstract = {The NASA Transiting Exoplanet Survey Satellite (TESS) is about to provide full-frame images of almost the entire sky. The amount of stellar data to be analysed represents hundreds of millions stars, which is several orders of magnitude more than the number of stars observed by the Convection, Rotation and planetary Transits satellite (CoRoT), and NASA Kepler and K2 missions. We aim at automatically classifying the newly observed stars with near real-time algorithms to better guide the subsequent detailed studies. In this paper, we present a classification algorithm built to recognise solar-like pulsators among classical pulsators. This algorithm relies on the global amount of power contained in the power spectral density (PSD), also known as the flicker in spectral power density (FliPer). Because each type of pulsating star has a characteristic background or pulsation pattern, the shape of the PSD at different frequencies can be used to characterise the type of pulsating star. The FliPer classifier (FliPerClass) uses different FliPer parameters along with the effective temperature as input parameters to feed a ML algorithm in order to automatically classify the pulsating stars observed by TESS. Using noisy TESS-simulated data from the TESS Asteroseismic Science Consortium (TASC), we classify pulsators with a 98% accuracy. Among them, solar-like pulsating stars are recognised with a 99% accuracy, which is of great interest for a further seismic analysis of these stars, which are like our Sun. Similar results are obtained when we trained our classifier and applied it to 27-day subsets of real Kepler data. FliPerClass is part of the large TASC classification pipeline developed by the TESS Data for Asteroseismology (T’DA) classification working group.}, author = {Bugnet, Lisa Annabelle and García, R. A. and Mathur, S. and Davies, G. R. and Hall, O. J. and Lund, M. N. and Rendle, B. M.}, issn = {1432-0746}, journal = {Astronomy & Astrophysics}, keywords = {Space and Planetary Science, Astronomy and Astrophysics}, publisher = {EDP Science}, title = {{FliPerClass: In search of solar-like pulsators among TESS targets}}, doi = {10.1051/0004-6361/201834780}, volume = {624}, year = {2019}, } @article{11623, abstract = {Brightness variations due to dark spots on the stellar surface encode information about stellar surface rotation and magnetic activity. In this work, we analyze the Kepler long-cadence data of 26,521 main-sequence stars of spectral types M and K in order to measure their surface rotation and photometric activity level. Rotation-period estimates are obtained by the combination of a wavelet analysis and autocorrelation function of the light curves. Reliable rotation estimates are determined by comparing the results from the different rotation diagnostics and four data sets. We also measure the photometric activity proxy Sph using the amplitude of the flux variations on an appropriate timescale. We report rotation periods and photometric activity proxies for about 60% of the sample, including 4431 targets for which McQuillan et al. did not report a rotation period. For the common targets with rotation estimates in this study and in McQuillan et al., our rotation periods agree within 99%. In this work, we also identify potential polluters, such as misclassified red giants and classical pulsator candidates. Within the parameter range we study, there is a mild tendency for hotter stars to have shorter rotation periods. The photometric activity proxy spans a wider range of values with increasing effective temperature. The rotation period and photometric activity proxy are also related, with Sph being larger for fast rotators. Similar to McQuillan et al., we find a bimodal distribution of rotation periods.}, author = {Santos, A. R. G. and García, R. A. and Mathur, S. and Bugnet, Lisa Annabelle and van Saders, J. L. and Metcalfe, T. S. and Simonian, G. V. A. and Pinsonneault, M. H.}, issn = {0067-0049}, journal = {The Astrophysical Journal Supplement Series}, keywords = {Space and Planetary Science, Astronomy and Astrophysics, methods: data analysis, stars: activity, stars: low-mass, stars: rotation, starspots, techniques: photometric}, number = {1}, publisher = {IOP Publishing}, title = {{Surface rotation and photometric activity for Kepler targets. I. M and K main-sequence stars}}, doi = {10.3847/1538-4365/ab3b56}, volume = {244}, year = {2019}, } @unpublished{11627, abstract = {For a solar-like star, the surface rotation evolves with time, allowing in principle to estimate the age of a star from its surface rotation period. Here we are interested in measuring surface rotation periods of solar-like stars observed by the NASA mission Kepler. Different methods have been developed to track rotation signals in Kepler photometric light curves: time-frequency analysis based on wavelet techniques, autocorrelation and composite spectrum. We use the learning abilities of random forest classifiers to take decisions during two crucial steps of the analysis. First, given some input parameters, we discriminate the considered Kepler targets between rotating MS stars, non-rotating MS stars, red giants, binaries and pulsators. We then use a second classifier only on the MS rotating targets to decide the best data analysis treatment.}, author = {Breton, S. N. and Bugnet, Lisa Annabelle and Santos, A. R. G. and Saux, A. Le and Mathur, S. and Palle, P. L. and Garcia, R. A.}, booktitle = {arXiv}, keywords = {asteroseismology, rotation, solar-like stars, kepler, machine learning, random forest}, title = {{Determining surface rotation periods of solar-like stars observed by the Kepler mission using machine learning techniques}}, doi = {10.48550/arXiv.1906.09609}, year = {2019}, } @unpublished{11630, abstract = {The second mission of NASA’s Kepler satellite, K2, has collected hundreds of thousands of lightcurves for stars close to the ecliptic plane. This new sample could increase the number of known pulsating stars and then improve our understanding of those stars. For the moment only a few stars have been properly classified and published. In this work, we present a method to automaticly classify K2 pulsating stars using a Machine Learning technique called Random Forest. The objective is to sort out the stars in four classes: red giant (RG), main-sequence Solar-like stars (SL), classical pulsators (PULS) and Other. To do this we use the effective temperatures and the luminosities of the stars as well as the FliPer features, that measures the amount of power contained in the power spectral density. The classifier now retrieves the right classification for more than 80% of the stars.}, author = {Saux, A. Le and Bugnet, Lisa Annabelle and Mathur, S. and Breton, S. N. and Garcia, R. A.}, booktitle = {arXiv}, keywords = {asteroseismology - methods, data analysis - thecniques, machine learning - stars, oscillations}, title = {{Automatic classification of K2 pulsating stars using machine learning techniques}}, doi = {10.48550/arXiv.1906.09611}, year = {2019}, } @inproceedings{11826, abstract = {The diameter, radius and eccentricities are natural graph parameters. While these problems have been studied extensively, there are no known dynamic algorithms for them beyond the ones that follow from trivial recomputation after each update or from solving dynamic All-Pairs Shortest Paths (APSP), which is very computationally intensive. This is the situation for dynamic approximation algorithms as well, and even if only edge insertions or edge deletions need to be supported. This paper provides a comprehensive study of the dynamic approximation of Diameter, Radius and Eccentricities, providing both conditional lower bounds, and new algorithms whose bounds are optimal under popular hypotheses in fine-grained complexity. Some of the highlights include: - Under popular hardness hypotheses, there can be no significantly better fully dynamic approximation algorithms than recomputing the answer after each update, or maintaining full APSP. - Nearly optimal partially dynamic (incremental/decremental) algorithms can be achieved via efficient reductions to (incremental/decremental) maintenance of Single-Source Shortest Paths. For instance, a nearly (3/2+epsilon)-approximation to Diameter in directed or undirected n-vertex, m-edge graphs can be maintained decrementally in total time m^{1+o(1)}sqrt{n}/epsilon^2. This nearly matches the static 3/2-approximation algorithm for the problem that is known to be conditionally optimal.}, author = {Ancona, Bertie and Henzinger, Monika H and Roditty, Liam and Williams, Virginia Vassilevska and Wein, Nicole}, booktitle = {46th International Colloquium on Automata, Languages, and Programming}, isbn = {978-3-95977-109-2}, issn = {1868-8969}, location = {Patras, Greece}, publisher = {Schloss Dagstuhl - Leibniz-Zentrum für Informatik}, title = {{Algorithms and hardness for diameter in dynamic graphs}}, doi = {10.4230/LIPICS.ICALP.2019.13}, volume = {132}, year = {2019}, } @inproceedings{11850, abstract = {Modern networked systems are increasingly reconfigurable, enabling demand-aware infrastructures whose resources can be adjusted according to the workload they currently serve. Such dynamic adjustments can be exploited to improve network utilization and hence performance, by moving frequently interacting communication partners closer, e.g., collocating them in the same server or datacenter. However, dynamically changing the embedding of workloads is algorithmically challenging: communication patterns are often not known ahead of time, but must be learned. During the learning process, overheads related to unnecessary moves (i.e., re-embeddings) should be minimized. This paper studies a fundamental model which captures the tradeoff between the benefits and costs of dynamically collocating communication partners on l servers, in an online manner. Our main contribution is a distributed online algorithm which is asymptotically almost optimal, i.e., almost matches the lower bound (also derived in this paper) on the competitive ratio of any (distributed or centralized) online algorithm.}, author = {Henzinger, Monika H and Neumann, Stefan and Schmid, Stefan}, booktitle = {SIGMETRICS'19: International Conference on Measurement and Modeling of Computer Systems}, isbn = {978-1-4503-6678-6}, location = {Phoenix, AZ, United States}, pages = {43–44}, publisher = {Association for Computing Machinery}, title = {{Efficient distributed workload (re-)embedding}}, doi = {10.1145/3309697.3331503}, year = {2019}, } @inbook{11847, abstract = {This paper serves as a user guide to the Vienna graph clustering framework. We review our general memetic algorithm, VieClus, to tackle the graph clustering problem. A key component of our contribution are natural recombine operators that employ ensemble clusterings as well as multi-level techniques. Lastly, we combine these techniques with a scalable communication protocol, producing a system that is able to compute high-quality solutions in a short amount of time. After giving a description of the algorithms employed, we establish the connection of the graph clustering problem to protein–protein interaction networks and moreover give a description on how the software can be used, what file formats are expected, and how this can be used to find functional groups in protein–protein interaction networks.}, author = {Biedermann, Sonja and Henzinger, Monika H and Schulz, Christian and Schuster, Bernhard}, booktitle = {Protein-Protein Interaction Networks}, editor = {Canzar, Stefan and Rojas Ringeling, Francisca}, isbn = {9781493998722}, issn = {1940-6029}, pages = {215–231}, publisher = {Springer Nature}, title = {{Vienna Graph Clustering}}, doi = {10.1007/978-1-4939-9873-9_16}, volume = {2074}, year = {2019}, } @inproceedings{11853, abstract = {We present a deterministic dynamic algorithm for maintaining a (1+ε)f-approximate minimum cost set cover with O(f log(Cn)/ε^2) amortized update time, when the input set system is undergoing element insertions and deletions. Here, n denotes the number of elements, each element appears in at most f sets, and the cost of each set lies in the range [1/C, 1]. Our result, together with that of Gupta~et~al.~[STOC'17], implies that there is a deterministic algorithm for this problem with O(f log(Cn)) amortized update time and O(min(log n, f)) -approximation ratio, which nearly matches the polynomial-time hardness of approximation for minimum set cover in the static setting. Our update time is only O(log (Cn)) away from a trivial lower bound. Prior to our work, the previous best approximation ratio guaranteed by deterministic algorithms was O(f^2), which was due to Bhattacharya~et~al.~[ICALP`15]. In contrast, the only result that guaranteed O(f) -approximation was obtained very recently by Abboud~et~al.~[STOC`19], who designed a dynamic algorithm with (1+ε)f-approximation ratio and O(f^2 log n/ε) amortized update time. Besides the extra O(f) factor in the update time compared to our and Gupta~et~al.'s results, the Abboud~et~al.~algorithm is randomized, and works only when the adversary is oblivious and the sets are unweighted (each set has the same cost). We achieve our result via the primal-dual approach, by maintaining a fractional packing solution as a dual certificate. This approach was pursued previously by Bhattacharya~et~al.~and Gupta~et~al., but not in the recent paper by Abboud~et~al. Unlike previous primal-dual algorithms that try to satisfy some local constraints for individual sets at all time, our algorithm basically waits until the dual solution changes significantly globally, and fixes the solution only where the fix is needed.}, author = {Bhattacharya, Sayan and Henzinger, Monika H and Nanongkai, Danupon}, booktitle = {60th Annual Symposium on Foundations of Computer Science}, isbn = {978-1-7281-4953-0}, issn = {2575-8454}, location = {Baltimore, MD, United States}, pages = {406--423}, publisher = {Institute of Electrical and Electronics Engineers}, title = {{A new deterministic algorithm for dynamic set cover}}, doi = {10.1109/focs.2019.00033}, year = {2019}, } @inproceedings{11851, abstract = {The minimum cut problem for an undirected edge-weighted graph asks us to divide its set of nodes into two blocks while minimizing the weighted sum of the cut edges. In this paper, we engineer the fastest known exact algorithm for the problem. State-of-the-art algorithms like the algorithm of Padberg and Rinaldi or the algorithm of Nagamochi, Ono and Ibaraki identify edges that can be contracted to reduce the graph size such that at least one minimum cut is maintained in the contracted graph. Our algorithm achieves improvements in running time over these algorithms by a multitude of techniques. First, we use a recently developed fast and parallel inexact minimum cut algorithm to obtain a better bound for the problem. Afterwards, we use reductions that depend on this bound to reduce the size of the graph much faster than previously possible. We use improved data structures to further lower the running time of our algorithm. Additionally, we parallelize the contraction routines of Nagamochi et al. . Overall, we arrive at a system that significantly outperforms the fastest state-of-the-art solvers for the exact minimum cut problem.}, author = {Henzinger, Monika H and Noe, Alexander and Schulz, Christian}, booktitle = {33rd International Parallel and Distributed Processing Symposium}, isbn = {978-1-7281-1247-3}, issn = {1530-2075}, location = {Rio de Janeiro, Brazil}, publisher = {Institute of Electrical and Electronics Engineers}, title = {{Shared-memory exact minimum cuts}}, doi = {10.1109/ipdps.2019.00013}, year = {2019}, } @inproceedings{11865, abstract = {We present the first sublinear-time algorithm that can compute the edge connectivity λ of a network exactly on distributed message-passing networks (the CONGEST model), as long as the network contains no multi-edge. We present the first sublinear-time algorithm for a distributed message-passing network sto compute its edge connectivity λ exactly in the CONGEST model, as long as there are no parallel edges. Our algorithm takes Õ(n1−1/353D1/353+n1−1/706) time to compute λ and a cut of cardinality λ with high probability, where n and D are the number of nodes and the diameter of the network, respectively, and Õ hides polylogarithmic factors. This running time is sublinear in n (i.e. Õ(n1−є)) whenever D is. Previous sublinear-time distributed algorithms can solve this problem either (i) exactly only when λ=O(n1/8−є) [Thurimella PODC’95; Pritchard, Thurimella, ACM Trans. Algorithms’11; Nanongkai, Su, DISC’14] or (ii) approximately [Ghaffari, Kuhn, DISC’13; Nanongkai, Su, DISC’14]. To achieve this we develop and combine several new techniques. First, we design the first distributed algorithm that can compute a k-edge connectivity certificate for any k=O(n1−є) in time Õ(√nk+D). The previous sublinear-time algorithm can do so only when k=o(√n) [Thurimella PODC’95]. In fact, our algorithm can be turned into the first parallel algorithm with polylogarithmic depth and near-linear work. Previous near-linear work algorithms are essentially sequential and previous polylogarithmic-depth algorithms require Ω(mk) work in the worst case (e.g. [Karger, Motwani, STOC’93]). Second, we show that by combining the recent distributed expander decomposition technique of [Chang, Pettie, Zhang, SODA’19] with techniques from the sequential deterministic edge connectivity algorithm of [Kawarabayashi, Thorup, STOC’15], we can decompose the network into a sublinear number of clusters with small average diameter and without any mincut separating a cluster (except the “trivial” ones). This leads to a simplification of the Kawarabayashi-Thorup framework (except that we are randomized while they are deterministic). This might make this framework more useful in other models of computation. Finally, by extending the tree packing technique from [Karger STOC’96], we can find the minimum cut in time proportional to the number of components. As a byproduct of this technique, we obtain an Õ(n)-time algorithm for computing exact minimum cut for weighted graphs.}, author = {Daga, Mohit and Henzinger, Monika H and Nanongkai, Danupon and Saranurak, Thatchaphol}, booktitle = {Proceedings of the 51st Annual ACM SIGACT Symposium on Theory of Computing}, isbn = {978-1-4503-6705-9}, issn = {0737-8017}, location = {Phoenix, AZ, United States}, pages = {343–354}, publisher = {Association for Computing Machinery}, title = {{Distributed edge connectivity in sublinear time}}, doi = {10.1145/3313276.3316346}, year = {2019}, } @inproceedings{11871, abstract = {Many dynamic graph algorithms have an amortized update time, rather than a stronger worst-case guarantee. But amortized data structures are not suitable for real-time systems, where each individual operation has to be executed quickly. For this reason, there exist many recent randomized results that aim to provide a guarantee stronger than amortized expected. The strongest possible guarantee for a randomized algorithm is that it is always correct (Las Vegas), and has high-probability worst-case update time, which gives a bound on the time for each individual operation that holds with high probability. In this paper we present the first polylogarithmic high-probability worst-case time bounds for the dynamic spanner and the dynamic maximal matching problem. 1. For dynamic spanner, the only known o(n) worst-case bounds were O(n3/4) high-probability worst-case update time for maintaining a 3-spanner, and O(n5/9) for maintaining a 5-spanner. We give a O(1)k log3(n) high-probability worst-case time bound for maintaining a (2k – 1)-spanner, which yields the first worst-case polylog update time for all constant k. (All the results above maintain the optimal tradeoff of stretch 2k – 1 and Õ(n1+1/k) edges.) 2. For dynamic maximal matching, or dynamic 2-approximate maximum matching, no algorithm with o(n) worst-case time bound was known and we present an algorithm with O(log5 (n)) high-probability worst-case time; similar worst-case bounds existed only for maintaining a matching that was (2 + ∊)-approximate, and hence not maximal. Our results are achieved using a new approach for converting amortized guarantees to worst-case ones for randomized data structures by going through a third type of guarantee, which is a middle ground between the two above: an algorithm is said to have worst-case expected update time α if for every update σ, the expected time to process σ is at most α. Although stronger than amortized expected, the worst-case expected guarantee does not resolve the fundamental problem of amortization: a worst-case expected update time of O(1) still allows for the possibility that every 1/f(n) updates requires Θ(f(n)) time to process, for arbitrarily high f(n). In this paper we present a black-box reduction that converts any data structure with worst-case expected update time into one with a high-probability worst-case update time: the query time remains the same, while the update time increases by a factor of O(log2(n)). Thus we achieve our results in two steps: (1) First we show how to convert existing dynamic graph algorithms with amortized expected polylogarithmic running times into algorithms with worst-case expected polylogarithmic running times. (2) Then we use our black-box reduction to achieve the polylogarithmic high-probability worst-case time bound. All our algorithms are Las-Vegas-type algorithms.}, author = {Bernstein, Aaron and Forster, Sebastian and Henzinger, Monika H}, booktitle = {30th Annual ACM-SIAM Symposium on Discrete Algorithms}, location = {San Diego, CA, United States}, pages = {1899--1918}, publisher = {Society for Industrial and Applied Mathematics}, title = {{A deamortization approach for dynamic spanner and dynamic maximal matching}}, doi = {10.1137/1.9781611975482.115}, year = {2019}, }