Search

We present the results of a search for Miras and long-period variables (LPVs) in M33 using griJHKS archival observations from the Canada–France–Hawaii Telescope. We use multiband information and machine learning techniques to identify and characterize these variables. We recover ∼1300 previously discovered Mira candidates and identify ∼13 000 new Miras and LPVs. We detect for the first time a clear first-overtone pulsation sequence among Mira candidates in this galaxy. We use O-rich, fundamental-mode Miras in the LMC and M33 to derive a distance modulus for the latter of μ = 24.629 ± 0.046 mag. [ABSTRACT FROM AUTHOR]

The SH0ES collaboration Hubble constant determination is in a ∼5σ difference with the Planck value, known as the Hubble tension. The accuracy of the Hubble constant measured with extragalactic Cepheids depends on robust stellar-crowding background estimation. Riess et al. (R20) compared the light-curve amplitudes of extragalactic and MW Cepheids to constrain an unaccounted systematic blending bias, |$\gamma =-0.029\pm 0.037\, \rm {mag}$|⁠ , which cannot explain the required, |$\gamma =0.24\pm 0.05\, \rm {mag}$|⁠ , to resolve the Hubble tension. Further checks by Riess et al. demonstrate that a possible blending is not likely related to the size of the crowding correction. We repeat the R20 analysis, with the following main differences: (1) we limit the extragalactic and MW Cepheids comparison to periods |$P\lesssim 50\, \rm {d}$|⁠ , since the number of MW Cepheids with longer periods is minimal; (2) we use publicly available data to recalibrate amplitude ratios of MW Cepheids in standard passbands; (3) we remeasure the amplitudes of Cepheids in NGC 5584 and NGC 4258 in two Hubble Space Telescope filters (F 555 W and F 350 LP) to improve the empirical constraint on their amplitude ratio A 555/ A 350. We show that the filter transformations introduce an |${\approx }0.04\, \rm {mag}$| uncertainty in determining γ, not included by R20. While our final estimate, |$\gamma =0.013\pm 0.057\, \rm {mag}$|⁠ , is consistent with the value derived by R20 and is consistent with no bias, the error is somewhat larger, and the best-fitting value is shifted by |${\approx }0.04\, \rm {mag}$| and closer to zero. Future observations, especially with JWST , would allow better calibration of γ. [ABSTRACT FROM AUTHOR]

The giant spiral galaxy M101 is host to the nearest recent Type Ia supernova (SN 2011fe) and thus has been extensively monitored in the near-infrared to study the late-time light curve of the SN. Leveraging this existing baseline of observations, we derive the first Mira-based distance to M101 by discovering and classifying a sample of 211 Miras with periods ranging from 240–400 days in the SN field. Combined with new Hubble Space Telescope (HST) WFC3/IR channel observations, our data set totals 11 epochs of F110W (HST YJ) and 13 epochs of F160W (HST H) data spanning ∼2900 days. We adopt absolute calibrations of the Mira period–luminosity relation based on geometric distances to the Large Magellanic Cloud and the water megamaser host galaxy NGC 4258, and find μ M101 = 29.10 ± 0.06 mag. This distance is in 1 σ agreement with most other recent Cepheid and tip of the red giant branch distance measurements to M101. Including the previous Mira SN Ia host, NGC 1559, and SN 2005df, we determine the fiducial SN Ia peak luminosity, M B 0 = − 19.27 ± 0.09 mag. With the Hubble diagram of supernovae Ia, we derive H 0 = 72.37 ± 2.97 km s−1 Mpc−1, a 4.1% measurement of H 0 using Miras. We find excellent agreement with recent Cepheid distance ladder measurements of H 0 and confirm previous indications that the local universe value of H 0 is higher than the early universe value at ∼95% confidence. Currently, the Mira-based H 0 measurement is still dominated by the statistical uncertainty in the SN Ia peak magnitude. [ABSTRACT FROM AUTHOR]

The three-rung distance ladder, which calibrates Type Ia supernovae (SNe Ia) through stellar distances linked to geometric measurements, provides the highest precision direct measurement of the Hubble constant. In light of the Hubble tension, it is important to test the individual components of the distance ladder. For this purpose, we report a measurement of the Hubble constant from 35 extragalactic Cepheid hosts measured by the SH0ES team, using their distances and redshifts at cz ≤ 3300 km sâˆ'1, instead of any more distant SNe Ia, to measure the Hubble flow. The Cepheid distances are calibrated geometrically in the Milky Way, NGC 4258, and the Large Magellanic Cloud. Peculiar velocities are a significant source of systematic uncertainty at z ∼ 0.01, and we present a formalism for both mitigating and quantifying their effects, making use of external reconstructions of the density and velocity fields in the nearby universe. We identify a significant source of uncertainty originating from different assumptions about the selection criteria of this sample, whether distance or redshift limited, as it was assembled over three decades. Modeling these assumptions yields central values ranging from H 0 = 71.7 to 76.4 km sâˆ'1 Mpcâˆ'1. Combining the four best-fitting selection models yields H 0 = 72.9 âˆ' 2.2 + 2.4 as a fiducial result, at 2.4 σ tension with Planck. While SNe Ia are essential for a precise measurement of H 0, unknown systematics in these supernovae are unlikely to be the source of the Hubble tension. [ABSTRACT FROM AUTHOR]

The Type Ia supernovae (SNe Ia) 2011by, hosted in NGC 3972, and 2011fe, hosted in M101, are optical 'twins,' having almost identical optical light-curve shapes, colours, and near-maximum-brightness spectra. However, SN 2011fe had significantly more ultraviolet (UV; 1600 < λ < 2500 Å) flux than SN 2011by before and at peak luminosity. Several theoretical models predict that SNe Ia with higher progenitor metallicity should (1) have additional UV opacity and thus lower UV flux; (2) have an essentially unchanged optical spectral-energy distribution; (3) have a similar optical light-curve shape; and (4) because of the excess neutrons, produce more stable Fe-group elements at the expense of radioactive 56Ni and thus have a lower peak luminosity. Following these predictions, Foley and Kirshner suggested that the difference in UV flux between SNe 2011by and 2011fe was the result of their progenitors having significantly different metallicities. They also measured a large, but insignificant, difference between the peak absolute magnitudes of the SNe (Δ M V, peak = 0.60 ± 0.36 mag), with SN 2011fe being more luminous. We present a new Cepheid-based distance to NGC 3972, substantially improving the precision of the distance measurement for SN 2011by. With these new data, we determine that the SNe have significantly different peak luminosities (Δ M V, peak = 0.335 ± 0.069 mag). Consequently, SN 2011fe produced 38 per cent more 56Ni than SN 2011by, consistent with predictions for progenitor metallicity differences for these SNe, although alternative models may also explain this difference. We discuss how progenitor metallicity differences can contribute to the intrinsic scatter for light-curve-shape-corrected SN luminosities, the use of 'twin' SNe for measuring distances, and implications for using SNe Ia for constraining cosmological parameters. [ABSTRACT FROM AUTHOR]

We present a calibration of the tip of the red giant branch (TRGB) in the Large Magellanic Cloud (LMC) on the Hubble Space Telescope (HST)/ACS F814W system. We use archival HST observations to derive blending corrections and photometric transformations for two ground-based wide-area imaging surveys of the Magellanic Clouds. We show that these surveys are biased bright by up to ∼0.1 mag in the optical due to blending, and that the bias is a function of local stellar density. We correct the LMC TRGB magnitudes from Jang & Lee and use the geometric distance from Pietrzyński et al. to obtain an absolute TRGB magnitude of. Applying this calibration to the TRGB magnitudes from Freedman et al. in SN Ia hosts yields a value for the Hubble constant of H0 = 72.4 ± 2.0 km s−1 Mpc−1 for their TRGB+SNe Ia distance ladder. The difference in the TRGB calibration and the value of H0 derived here and by Freedman et al. primarily results from their overestimate of the LMC extinction, caused by inconsistencies in their different sources of TRGB photometry for the Magellanic Clouds. Using the same source of photometry (OGLE) for both Clouds and applying the aforementioned corrections yields a value for the LMC I-band TRGB extinction that is lower by 0.06 mag, consistent with independent OGLE reddening maps used by us and by Jang & Lee to calibrate TRGB and determine H0. [ABSTRACT FROM AUTHOR]

We present the final distance measurements for the 2MASS Tully–Fisher (2MTF) survey. The final 2MTF catalogue contains 2062 nearby spiral galaxies in the CMB frame velocity range of 600 < cz < 10 000 km s−1 with a mean velocity of 4805 km s−1. The main update in this release is the replacement of some archival HI data with newer ALFALFA data. Using the 2MTF template relation, we calculate the distances and peculiar velocities of all 2MTF galaxies. The mean uncertainties of the linear distance measurements are around 22 per  cent in all three infrared bands. 2MTF measurements agree well with the distances from the Cosmicflows-3 compilation, which contains 1117 common galaxies, including 28 with SNIa distance measurements. Using distances estimated from the '3-bands combined' 2MTF sample and a χ2 minimization method, we find best-fitting bulk flow amplitudes of 308 ± 26 km s−1, 318 ± 29 km s−1, and 286 ± 25 km s−1 at depths of RI  = 20, 30 and 40 |$~h^{-1}\, {\rm Mpc}$|⁠ , respectively, which is consistent with the ΛCDM model and with previous 2MTF results with different estimation techniques and a preliminary catalogue. [ABSTRACT FROM AUTHOR]

We present the results of prompt optical follow-up of the electromagnetic counterpart of GW170817 by the Transient Optical Robotic Observatory of the South Collaboration (TOROS). We detected highly significant dimming in the light curves of the counterpart over the course of only 80 minutes of observations obtained ~35 hr after the trigger with the T80-South telescope. A second epoch of observations, obtained ~59 hr after the event with the EABA 1.5m telescope, confirms the fast fading nature of the transient. The observed colors of the counterpart suggest that this event was a "blue kilonova" relatively free of lanthanides. [ABSTRACT FROM AUTHOR]

We present measurements of the velocity power spectrum and constraints on the growth rate of structure fσ8, at redshift zero, using the peculiar motions of 2062 galaxies in the completed 2MASS Tully–Fisher survey (2MTF). To accomplish this we introduce a model for fitting the velocity power spectrum including the effects of non-linear redshift space distortions (RSD), allowing us to recover unbiased fits down to scales k=0.2 h Mpc-1 without the need to smooth or grid the data. Our fitting methods are validated using a set of simulated 2MTF surveys. Using these simulations we also identify that the Gaussian distributed estimator for peculiar velocities of Watkins & Feldman is suitable for measuring the velocity power spectrum, but sub-optimal for the 2MTF data compared to using magnitude fluctuations δm, and that, whilst our fits are robust to a change in fiducial cosmology, future peculiar velocity surveys with more constraining power may have to marginalize over this. We obtain scale-dependent constraints on the growth rate of structure in two bins, finding fσ8 = [0.55-0.13+0.16, 0.40-0.17+0.16] in the ranges k = [0.007-0.055, 0.55-0.150] h Mpc-1. We also find consistent results using four bins. Assuming scale-independence we find a value fσ8 = 0.51-0.08+0.09, a ∼16 per cent measurement of the growth rate. Performing a consistency check of general relativity (GR) and combining our results with cosmic microwave background data only we find γ = 0.45-0.11+0.10, a remarkable constraint considering the small number of galaxies. All of our results are completely independent of the effects of galaxy bias, and fully consistent with the predictions of GR (scale-independent fσ8 and γ ≈ 0.55). [ABSTRACT FROM AUTHOR]

We present the results of prompt optical follow-up of the electromagnetic counterpart of GW170817 by the Transient Optical Robotic Observatory of the South Collaboration (TOROS). We detected highly significant dimming in the light curves of the counterpart over the course of only 80 minutes of observations obtained ~35 hr after the trigger with the T80-South telescope. A second epoch of observations, obtained ~59 hr after the event with the EABA 1.5m telescope, confirms the fast fading nature of the transient. The observed colors of the counterpart suggest that this event was a "blue kilonova" relatively free of lanthanides. [ABSTRACT FROM AUTHOR]

We present a detailed statistical analysis of possible non-linearities in the period-luminosity (PL), period-Wesenheit (PW) and period-colour (PC) relations for Cepheid variables in the Large Magellanic Cloud (LMC) at optical (VI) and near-infrared (JHKs) wavelengths. We test for the presence of possible non-linearities and determine their statistical significance by applying a variety of robust statistical tests (F-test, random-walk, testimator and the Davies test) to optical data from third phase of the Optical Gravitational Lensing Experiment and near-infrared data from Large Magellanic Cloud Near-Infrared Synoptic Survey. For fundamental-mode Cepheids, we find that the optical PL, PW and PC relations are non-linear at 10 d. The near-infrared PL and the WH V,I relations are nonlinear around 18 d; this break is attributed to a distinct variation in mean Fourier amplitude parameters near this period for longer wavelengths as compared to optical bands. The near-infrared PW relations are also non-linear except for the WH,Ks relation. For firstovertone mode Cepheids, a significant change in the slope of PL, PW and PC relations is found around 2.5 d only at optical wavelengths. We determine a global slope of -3.212 ± 0.013 for the WH V,I relation by combining our LMC data with observations of Cepheids in Supernovae host galaxies. We find this slope to be consistent with the corresponding LMC relation at short periods, and significantly different to the long-period value. We do not find any significant difference in the slope of the global-fit solution using a linear or non-linear LMC PL relation as calibrator, but the linear version provides a two times better constraint on the slope and metallicity coefficient. [ABSTRACT FROM AUTHOR]

Using the Tully-Fisher relation, we derive peculiar velocities for the 2MASS Tully-Fisher survey and describe the velocity field of the nearby Universe. We use adaptive kernel smoothing to map the velocity field, and compare it to reconstructions based on the redshift space galaxy distributions of the 2MASS Redshift Survey (2MRS) and the IRAS Point Source Catalog Redshift Survey (PSCz). With a standard χ² minimization fit to the models, we find that the PSCz model provides a better fit to the 2MTF velocity field data than does the 2MRS model, and provides a value of ß in greater agreement with literature values. However, when we subtract away the monopole deviation in the velocity zero-point between data and model, the 2MRS model also produces a value of β in agreement with literature values. We also calculate the 'residual bulk flow': the component of the bulk flow not accounted for by the models. This is ~250 km s-1 when performing the standard fit, but drops to ~150 km s-1 for both models when the aforementioned monopole offset between data and models is removed. This smaller number is more in line with theoretical expectations, and suggests that the models largely account for the major structures in the nearby Universe responsible for the bulk velocity. [ABSTRACT FROM AUTHOR]

We present a light-curve analysis of fundamental-mode Galactic and Large Magellanic Cloud (LMC) Cepheids based on the Fourier decomposition technique. We have compiled light-curve data for Galactic and LMC Cepheids in optical (VI), near-infrared (JHKs) and mid-infrared (3.6 and 4.5 μm) bands from the literature and determined the variation of their Fourier parameters as a function of period and wavelength. We observed a decrease in Fourier amplitude parameters and an increase in Fourier phase parameters with increasing wavelengths at a given period. We also found a decrease in the skewness and acuteness parameters as a function of wavelength at a fixed period. We applied a binning method to analyse the progression of the mean Fourier parameters with period and wavelength. We found that for periods longer than about 20 d, the values of the Fourier amplitude parameters increase sharply for shorter wavelengths as compared to wavelengths longer than the J band. We observed the variation of the Hertzsprung progression with wavelength. The central period of the Hertzsprung progression was found to increase with wavelength in the case of the Fourier amplitude parameters and decrease with increasing wavelength in the case of phase parameters. We also observed a small variation of the central period of the progression between the Galaxy and LMC, presumably related to metallicity effects. These results will provide useful constraints for stellar pulsation codes that incorporate stellar atmosphere models to produce Cepheid light curves in various bands. [ABSTRACT FROM AUTHOR]

Using the 2MASS near-infrared photometry and high-signal-to-noise H i 21-cm data from the Arecibo, Green Bank, Nancay, and Parkes telescopes, we calculate the redshift-independent distances and peculiar velocities of 2018 bright inclined spiral galaxies over the whole sky. This project is part of the 2MASS Tully-Fisher survey (2MTF), aiming to map the galaxy peculiar velocity field within 100 h−1 Mpc, with an all-sky coverage apart from Galactic latitudes |b| < 5°. A χ2 minimization method was adopted to analyse the Tully–Fisher peculiar velocity field in J, H, and K bands, using a Gaussian filter. We combine information from the three wavebands, to provide bulk flow measurements of 310.9 ± 33.9 , 280.8 ± 25.0, and 292.3 ± 27.8 km s−1 at depths of 20, 30, and 40 h−1 Mpc, respectively. Each of these bulk flow vectors points in a direction similar to those found by previous measurements. At each of the three depths, the bulk flow magnitude is consistent with predictions made by the Λ cold dark matter (ΛCDM) model at the 1σ level. The maximum likelihood and minimum variance method were also used to analyse the 2MTF samples, giving similar results. [ABSTRACT FROM PUBLISHER]

We present H i 21 cm observations of 1194 galaxies out to a redshift of 10 000 km s−1 selected as inclined spirals (i ≳ 60°) from the 2MASS redshift survey. These observations were carried out at the National Radio Astronomy Observatory Robert C. Byrd Green Bank Telescope (GBT). This observing programme is part of the 2MASS Tully–Fisher (2MTF) survey. This project will combine H i widths from these GBT observations with those from further dedicated observing at the Parkes Telescope, from the Arecibo Legacy Fast Arecibo L-band Feed Array survey at Arecibo, and S/N > 10 and spectral resolution vres < 10 km s−1 published widths from a variety of telescopes. We will use these H i widths along with 2MASS photometry to estimate Tully–Fisher distances to nearby spirals and investigate the peculiar velocity field of the local Universe. In this paper, we report on detections of neutral hydrogen in emission in 727 galaxies, and measure good signal to noise and symmetric H i global profiles suitable for use in the Tully–Fisher relation in 484. [ABSTRACT FROM PUBLISHER]

In 2008 January the 24th Chinese expedition team successfully deployed the Chinese Small Telescope ARray (CSTAR) to Dome A, the highest point on the Antarctic plateau. CSTAR consists of four 14.5cm optical telescopes, each with a different filter (g, r, i and open) and has a 4.5°×4.5° field of view (FOV). Based on the CSTAR data, initial statistics of astronomical observational site quality and light curves of variable objects were obtained. To reach higher photometric quality, we are continuing to work to overcome the effects of uneven cirrus cloud cirrus, optical “ghosts” and intra-pixel sensitivity. The snow surface stability is also tested for further astronomical observational instrument and for glaciology studies. [ABSTRACT FROM PUBLISHER]

In 2008 January the 24th Chinese expedition team successfully deployed the Chinese Small Telescope ARray (CSTAR) to Dome A, the highest point on the Antarctic plateau. CSTAR consists of four 14.5cm optical telescopes, each with a different filter (g, r, i and open) and has a 4.5°×4.5° field of view (FOV). Based on the CSTAR data, initial statistics of astronomical observational site quality and light curves of variable objects were obtained. To reach higher photometric quality, we are continuing to work to overcome the effects of uneven cirrus cloud cirrus, optical “ghosts” and intra-pixel sensitivity. The snow surface stability is also tested for further astronomical observational instrument and for glaciology studies. [ABSTRACT FROM PUBLISHER]

Stellar-mass black holes are found in X-ray-emitting binary systems, where their mass can be determined from the dynamics of their companion stars. Models of stellar evolution have difficulty producing black holes in close binaries with masses more than ten times that of the Sun (>10; ref. 4), which is consistent with the fact that the most massive stellar black holes known so far all have masses within one standard deviation of 10. Here we report a mass of (15.65 ± 1.45) for the black hole in the recently discovered system M 33 X-7, which is located in the nearby galaxy Messier 33 (M 33) and is the only known black hole that is in an eclipsing binary. To produce such a massive black hole, the progenitor star must have retained much of its outer envelope until after helium fusion in the core was completed. On the other hand, in order for the black hole to be in its present 3.45-day orbit about its (70.0 ± 6.9) companion, there must have been a ‘common envelope’ phase of evolution in which a significant amount of mass was lost from the system. We find that the common envelope phase could not have occurred in M 33 X-7 unless the amount of mass lost from the progenitor during its evolution was an order of magnitude less than what is usually assumed in evolutionary models of massive stars. [ABSTRACT FROM AUTHOR]

We present the reconstructed real-space density and the predicted velocity fields from the Two-Micron All-Sky Redshift Survey (2MRS). The 2MRS is the densest all-sky redshift survey to date and includes about 23 200 galaxies with extinction-corrected magnitudes brighter than . Our method is based on the expansion of these fields in Fourier–Bessel functions. Within this framework, the linear redshift distortions only affect the density field in the radial direction and can easily be deconvolved using a distortion matrix. Moreover, in this coordinate system, the velocity field is related to the density field by a simple linear transformation. The shot noise errors in the reconstructions are suppressed by means of a Wiener filter which yields a minimum variance estimate of the density and velocity fields. Using the reconstructed real-space density fields, we identify all major superclusters and voids. At , our reconstructed velocity field indicates a backside infall to the Great Attractor region of in the Local Group frame and in the cosmic microwave background (CMB) frame and β is the redshift distortion parameter. The direction of the reconstructed dipole agrees well with the dipole derived by Erdoğdu et al. The misalignment between the reconstructed 2MRS and the CMB dipoles drops to 13° at around but then increases at larger distances. [ABSTRACT FROM AUTHOR]

We describe an approach to automate the classification of Cepheid variable stars into two subtypes according to their pulsation mode. Automating such classification is relevant to obtain a precise determination of distances to nearby galaxies, which in addition helps reduce the uncertainty in the current expansion of the universe. One main difficulty lies in the compatibility of models trained using different galaxy datasets; a model trained using a training dataset may be ineffectual on a testing set. A solution to such difficulty is to adapt predictive models across domains; this is necessary when the training and testing sets do not follow the same distribution. The gist of our methodology is to train a predictive model on a nearby galaxy (e.g., Large Magellanic Cloud), followed by a model-adaptation step to make the model operable on other nearby galaxies. We follow a parametric approach to density estimation by modeling the training data (anchor galaxy) using a mixture of linear models. We then use maximum likelihood to compute the right amount of variable displacement, until the testing data closely overlaps the training data. At that point, the model can be directly used in the testing data (target galaxy). [ABSTRACT FROM PUBLISHER]

The past two decades have seen a significant advancement in the detection, classification and understanding of exoplanets and binary star systems. The vast majority of these systems consist of stars on the main sequence or on the giant branch, leading to a dearth of knowledge of properties at early times (< 50 Myr). Only one transiting planet candidate and a dozen eclipsing binaries are known among pre-main sequence objects, yet these are the systems that can provide the best constraints on stellar and planetary formation models. We have recently completed a photometric survey of 3 young (< 50 Myr), nearby (D< 150 pc) moving groups with a small-aperture instrument, nicknamed "AggieCam". We detected 7 candidate Hot Jupiters and over 200 likely pre-main sequence binaries, which are now being followed up photometrically and spectroscopically. [ABSTRACT FROM AUTHOR]

A correction to the article "A 3% Solution: Determination of the Hubble Constant With the Hubble Space Telescope and Wide Field Camera," by Adam G. Riess and colleagues, is presented.