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541. Cepheids and companions in M33 from HST images
ID:
ivo://CDS.VizieR/J/AJ/144/113
Title:
Cepheids and companions in M33 from HST images
Short Name:
J/AJ/144/113
Date:
21 Oct 2021
Publisher:
CDS
Description:
A precise and accurate determination of the Hubble constant based on Cepheid variables requires proper characterization of many sources of systematic error. One of these is stellar blending, which biases the measured fluxes of Cepheids and the resulting distance estimates. We study the blending of 149 Cepheid variables in M33 by matching archival Hubble Space Telescope data with images obtained at the Wisconsin-Indiana-Yale-NOAO (WIYN) 3.5m telescope, which differ by a factor of 10 in angular resolution. We find that 55%+/-4% of the Cepheids have no detectable nearby companions that could bias the WIYN V-band photometry, while the fraction of Cepheids affected below the 10% level is 73%+/-4%. The corresponding values for the I band are 60%+/-4% and 72%+/-4%, respectively. We find no statistically significant difference in blending statistics as a function of period or surface brightness. Additionally, we report all the detected companions within 2" of the Cepheids (equivalent to 9pc at the distance of M33) which may be used to derive empirical blending corrections for Cepheids at larger distances.
542. Cepheids HST amplitudes in V- and H-band
ID:
ivo://CDS.VizieR/J/ApJ/896/L43
Title:
Cepheids HST amplitudes in V- and H-band
Short Name:
J/ApJ/896/L43
Date:
21 Mar 2022 07:02:57
Publisher:
CDS
Description:
The accuracy of the Hubble constant measured with extragalactic Cepheids depends on robust photometry and background estimation in the presence of stellar crowding. The conventional approach accounts for crowding by sampling backgrounds near Cepheids and assuming that they match those at their positions. We show a direct consequence of crowding by unresolved sources at Cepheid sites is a reduction in the fractional amplitudes of their light curves. We use a simple analytical expression to infer crowding directly from the light curve amplitudes of >200 Cepheids in three Type Ia supernovae hosts and NGC4258 as observed by Hubble Space Telescope-the first near-infrared amplitudes measured beyond the Magellanic Clouds. Where local crowding is minimal, we find near-infrared amplitudes match Milky Way Cepheids at the same periods. At greater stellar densities we find that the empirically measured amplitudes match the values predicted (with no free parameters) from crowding assessed in the conventional way from local regions, confirming their accuracy for estimating the background at the Cepheid locations. Extragalactic Cepheid amplitudes would need to be ~20% smaller than measured to indicate additional, unrecognized crowding as a primary source of the present discrepancy in H0. Rather, we find the amplitude data constrains a systematic mis-estimate of Cepheid backgrounds to be 0.029R+/-0.037mag, more than 5x smaller than the size of the present ~0.2mag tension in H0. We conclude that systematic errors in Cepheid backgrounds do not provide a plausible resolution to the Hubble tension.
543. Cepheids in M101 observed with HST
ID:
ivo://CDS.VizieR/J/ApJ/733/124
Title:
Cepheids in M101 observed with HST
Short Name:
J/ApJ/733/124
Date:
21 Oct 2021
Publisher:
CDS
Description:
We accurately determine a new Cepheid distance to M101 (NGC 5457) using archival Hubble Space Telescope (HST)/Advanced Camera for Surveys V and I time series photometry of two fields within the galaxy. We make a slight modification to the ISIS image subtraction package to obtain optimal differential light curves from HST data. We discovered 827 Cepheids with periods between 3 and 80 days, the largest extragalactic sample of Cepheids observed with HST by a factor of two. With this large Cepheid sample, we find that the relative distance of M101 from the Large Magellanic Cloud is {Delta}{mu}_LMC_=10.63+/-0.04 (random) +/-0.06 (systematic) mag. If we use the geometrically determined maser distance to NGC 4258 as our distance anchor, the distance modulus of M101 is {mu}_0_=29.04+/-0.05 (random) +/-0.18 (systematic) mag or D=6.4+/-0.2 (random) +/-0.5 (systematic) Mpc. The uncertainty is dominated by the maser distance estimate (+/-0.15mag), which should improve over the next few years.
544. Cepheids in M31 - PAndromeda Cepheid sample
ID:
ivo://CDS.VizieR/J/AJ/156/130
Title:
Cepheids in M31 - PAndromeda Cepheid sample
Short Name:
J/AJ/156/130
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the largest Cepheid sample in M31 based on the complete Pan-STARRS1 survey of Andromeda (PAndromeda) in the r_P1_, i_P1_, and g_P1_ bands. We find 2686 Cepheids with 1662 fundamental-mode Cepheids, 307 first-overtone Cepheids, 278 type II Cepheids, and 439 Cepheids with undetermined Cepheid type. Using the method developed by Kodric et al. (2013, , Cat. J/AJ/145/106), we identify Cepheids by using a three-dimensional parameter space of Fourier parameters of the Cepheid light curves combined with a color cut and other selection criteria. This is an unbiased approach to identify Cepheids and results in a homogeneous Cepheid sample. The period-luminosity relations obtained for our sample have smaller dispersions than in our previous work. We find a broken slope that we previously observed with HST data in Kodric et al. (2013, , Cat. J/AJ/145/106), albeit with a lower significance.
545. Cetus dSph RR Lyrae
ID:
ivo://CDS.VizieR/J/MNRAS/422/89
Title:
Cetus dSph RR Lyrae
Short Name:
J/MNRAS/422/89
Date:
21 Oct 2021
Publisher:
CDS
Description:
We investigate the variable star content of the isolated, Local Group, dwarf spheroidal (dSph) galaxy Cetus. Multi-epoch, wide-field images collected with the Very Large Telescope/Visible Multiobject Spectrograph camera allowed us to detect 638 variable stars (630 RR Lyrae stars and eight anomalous Cepheids), 475 of which are new detections. We present a full catalogue of periods, amplitudes and mean magnitudes.
546. Cetus dSph stellar chemo-kinematics
ID:
ivo://CDS.VizieR/J/A+A/618/A122
Title:
Cetus dSph stellar chemo-kinematics
Short Name:
J/A+A/618/A122
Date:
21 Oct 2021
Publisher:
CDS
Description:
Cetus is an isolated, dwarf spheroidal (dSph) galaxy at a distance of 755kpc. In order to quantify its stellar chemo-kinematical properties, we observed individual red giants branch stars in Cetus with the Very Large Telescope (VLT) FORS2 instrument, in Mask eXchange Unit (MXU) configuration. The kinematic analysis shows that Cetus is a mainly pressure-supported ({sigma}_v_=11.0^+1.6^_-1.3_km/s), dark-matter-dominated system (M_1/2_/L_V_=23.9^+9.7^_-8.9_M_{sun}_/L_{sun}_) with no significant signs of internal rotation. We find Cetus to be a metal-poor system with a significant metallicity spread (median [Fe/H]=-1.71dex, median-absolute-deviation =0.49dex), as expected for its stellar mass. We report the presence of a mild metallicity gradient compatible with those found in other dSphs of the same luminosity; we trace the presence of a stellar population gradient also in the spatial distribution of stars in different evolutionary phases in ancillary photometric data. There are tentative indications of two chemo-kinematically distinct sub-populations, with the more metal-poor stars showing a hotter kinematics than the metal-richer ones. Our results add Cetus to the growing scatter in stellar-dark matter halo properties in low-mass galactic systems. The presence of a metallicity gradient akin to those found in similar systems inhabiting different environments may hint at metallicity gradients in Local Group early-type dwarfs being driven by internal mechanisms.
547. 3C 279 Event Horizon Telescope imaging
ID:
ivo://CDS.VizieR/J/A+A/640/A69
Title:
3C 279 Event Horizon Telescope imaging
Short Name:
J/A+A/640/A69
Date:
21 Oct 2021
Publisher:
CDS
Description:
3C 279 is an archetypal blazar with a prominent radio jet that show broadband flux density variability across the entire electromagnetic spectrum. We use an ultra-high angular resolution technique - global Very Long Baseline Interferometry (VLBI) at 1.3mm (230GHz) - to resolve the innermost jet of 3C 279 in order to study its fine-scale morphology close to the jet base where highly variable gamma-ray emission is thought to originate, according to various models. The source was observed during four days in April 2017 with the Event Horizon Telescope (EHT) at 230 GHz, including the phased Atacama Large Millimeter/submillimeter Array (ALMA), at an angular resolution of ~20uarcsec (at a redshift of z=0.536 this corresponds to ~0.13pc, ~1700 Schwarzschild radii with a black hole mass M_BH_=8x10^8^M_{sun}_). Imaging and model-fitting techniques were applied to the data to parameterize the fine-scale source structure and its variation. We find a multicomponent inner jet morphology with the northernmost component elongated perpendicular to the direction of the jet, as imaged at longer wavelengths. The elongated nuclear structure is consistent on all four observing days and across different imaging methods and model-fitting techniques, and therefore appears robust. Owing to its compactness and brightness, we associate the northern nuclear structure as the VLBI "core". This morphology can be interpreted as either a broad resolved jet base or a spatially bent jet. We also find significant day-to-day variations in the closure phases, which appear most pronounced on the triangles with the longest baselines. Our analysis shows that this variation is related to a systematic change of the source structure. Two inner jet components move non-radially at apparent speeds of ~15c and ~20c (~1.3 and ~1.7uarcsec/day, respectively), which more strongly supports the scenario of traveling shocks or instabilities in a bent, possibly rotating jet. The observed apparent speeds are also coincident with the 3C 279 large-scale jet kinematics observed at longer (cm) wavelengths, suggesting no significant jet acceleration between the 1.3mm core and the outer jet. The intrinsic brightness temperature of the jet components are <~10^10^K, a magnitude or more lower than typical values seen at >=7mm wavelengths. The low brightness temperature and morphological complexity suggest that the core region of 3C279 becomes optically thin at short (mm) wavelengths.
548. CF-HiZELS survey
ID:
ivo://CDS.VizieR/J/MNRAS/451/2303
Title:
CF-HiZELS survey
Short Name:
J/MNRAS/451/2303
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present results from the largest contiguous narrow-band survey in the near-infrared. We have used the wide-field infrared camera/Canada-France-Hawaii Telescope and the lowOH2 filter (1.187+/-0.005{mu}m) to survey ~10deg^2^ of contiguous extragalactic sky in the SA22 field. A total of ~6000 candidate emission-line galaxies are found. We use deep ugrizJK data to obtain robust photometric redshifts. We combine our data with the High-redshift(Z) Emission Line Survey (HiZELS), explore spectroscopic surveys (VVDS, VIPERS) and obtain our own spectroscopic follow-up with KMOS, FMOS and MOSFIRE to derive large samples of high-redshift emission-line selected galaxies: 3471 H{alpha} emitters at z=0.8, 1343 [OIII] + H{beta} emitters at z=1.4 and 572 [OII] emitters at z=2.2. We probe comoving volumes of >10^6^Mpc^3^ and find significant overdensities, including an 8.5{sigma} (spectroscopically confirmed) overdensity of H{alpha} emitters at z=0.81. We derive H{alpha}, [OIII] + H{beta} and [OII] luminosity functions at z=0.8, 1.4, 2.2, respectively, and present implications for future surveys such as Euclid. Our uniquely large volumes/areas allow us to subdivide the samples in thousands of randomized combinations of areas and provide a robust empirical measurement of sample/cosmic variance. We show that surveys for star-forming/emission-line galaxies at a depth similar to ours can only overcome cosmic-variance (errors <10 percent) if they are based on volumes >5x10^5^Mpc^3^; errors on L* and {phi}* due to sample (cosmic) variance on surveys probing ~10^4^ and ~10^5^Mpc^3^ are typically very high: ~300 and ~40-60 percent, respectively.
549. CFHQSIR survey
ID:
ivo://CDS.VizieR/J/A+A/616/A55
Title:
CFHQSIR survey
Short Name:
J/A+A/616/A55
Date:
21 Oct 2021
Publisher:
CDS
Description:
The Canada-France-Hawaii Telescope Legacy Survey (CFHTLS) has been conducted over a five-year period at the CFHT with the MegaCam instrument, totaling 450 nights of observations. The Wide Synoptic Survey is one component of the CFHTLS, covering 155 square degrees in four patches of 23 to 65 square degrees through the whole MegaCam filter set (u*, g', r', i', z') down to i'_{AB} = 24.5. With the motivation of searching for high-redshift quasars at redshifts above 6.5, we extend the multi-wavelength CFHTLS-Wide data in the Y-band down to magnitudes of {sim} 22.5 for point sources (5{sigma}). We observed the four CFHTLS-Wide fields (except one quarter of the W3 field) in the Y-band with the WIRCam instrument (Wide-field InfraRed Camera) at the CFHT. Each field was visited twice, at least three weeks apart. Each visit consisted of two dithered exposures. The images are reduced with the Elixir software used for the CFHTLS and modified to account for the properties of near-InfraRed (IR) data. Two series of image stacks are subsequently produced: four-image stacks for each WIRCam pointing, and one-square- degree tiles matched to the format of the CFHTLS data release. Photometric calibration is performed on stars by fitting stellar spectra to their CFHTLS photometric data and extrapolating their Y-band magnitudes. After corrections accounting for correlated noise, we measure a limiting magnitude of Y_{AB}~=22.4 for point sources (5{sigma}) in an aperture diameter of 0.93 arcsecs, over 130 square degrees. We produce a multi-wavelength catalogue combining the CFHTLS-Wide optical data with our CFHQSIR (Canada-France High-z quasar survey in the near-InfraRed) Y-band data. We derive the Y-band number counts and compare them to the Vista Deep Extragalactic Observations survey (VIDEO). We find that the addition of the CFHQSIR Y-band data to the CFHTLS optical data increases the accuracy of photometric redshifts and reduces the outlier rate from 13.8% to 8.8% in the redshift range 1.05<~z<~1.2. The images and the catalogue for 8.6 million sources down to [(z'>=23.5) {lor} (Y>=23.0)] are released and available at the following URL: http://apps.canfar.net/storage/list/cjw/cfhqsir
550. CFHTLenS galaxy bias and redshift distribution
ID:
ivo://CDS.VizieR/J/A+A/646/A71
Title:
CFHTLenS galaxy bias and redshift distribution
Short Name:
J/A+A/646/A71
Date:
21 Oct 2021
Publisher:
CDS
Description:
Galaxy models predict a tight relation between the clustering of galaxies and dark matter on cosmological scales, but predictions differ notably in the details. We used this opportunity and tested two semi-analytic models by the Munich and Durham groups with data from the Canada-France-Hawaii Telescope Lensing Survey (CFHTLenS). For the test we measured the scale-dependent galaxy bias factor b(k) and correlation factor r(k) from linear to non-linear scales of k=~10h/Mpc at two redshifts z{bar}=0.35, 0.51 for galaxies with stellar mass between 5x10^9^ and 3x10^11^h_70_^-2^M_{sun|_. Our improved gravitational lensing technique accounts for the intrinsic alignment of sources and the magnification of lens galaxies for better constraints for the galaxy-matter correlation r(k). Galaxy bias in CFHTLenS increases with k and stellar mass; it is colour-dependent, revealing the individual footprints of galaxy types. Despite a reasonable model agreement for the relative change with both scale and galaxy properties, there is a clear conflict for b(k) with no model preference: the model galaxies are too weakly clustered. This may flag a model problem at z>~0.3 for all stellar masses. As in the models, however, there is a high correlation r(k) between matter and galaxy density on all scales, and galaxy bias is typically consistent with a deterministic bias on linear scales. Only our blue and low-mass galaxies of about 7x10^9^h_70_^-2^M_{sun}_ at z{bar}=0.51 show, contrary to the models, a weak tendency towards a stochastic bias on linear scales where rls=0.75+/-0.14(stat.)+/-0.06(sys.). This result is of interest for cosmological probes, such as EG, that rely on a deterministic galaxy bias. We provide Monte Carlo realisations of posterior constraints for b(k) and r(k) in CFHTLenS for every galaxy sample in this paper at the CDS.