We present new B-V color-magnitude diagrams for Fornax globular cluster 3 and the surrounding field where our data reach one magnitude below the horizontal branch which is at V_HB_=21.28. After subtracting the field stars from the cluster CMD, we found no evidence for an intrinsic width of the red giant branch because the scatter is only slightly wider than the photometric errors. We determine that there is an intrinsic width to the horizontal branch because the scatter is larger than the photometric errors. After comparing our data with earlier photometry, we find 7 possible variable stars, both within and outside the instability strip, out of a total of 74 horizontal branch stars. We calculate the horizontal branch type of cluster 3 to be of intermediate color, -0.110+/-0.104, which when compared to Fornax cluster 1, having similar metallicity, suggests a second-parameter pair. Five carbon star candidates identified by Jorgensen & Jimenez (1997, Cat. <J/A+A/317/54>) are marked in the field-subtracted color-magnitude diagram. (c) 1997 American Astronomical Society.
The Fornax cluster provides an unparalleled opportunity of investigating the formation and evolution of early-type galaxies in a dense environment in detail. We aim at kinematically characterising photometrically detected globular cluster (GC) candidates in the core of the cluster. We used VLT/VIMOS spectroscopic data from the FVSS survey in the Fornax cluster, covering one square degree around the central massive galaxy NGC 1399. We confirm a total of 777 GCs, almost doubling previously detected GCs, using the same dataset as was used before. Combined with previous literature radial velocity measurements of GCs in Fornax, we compile the most extensive spectroscopic GC sample of 2341 objects in this environment. We found that red GCs are mostly concentrated around major galaxies, while blue GCs are kinematically irregular and are widely spread throughout the core region of the cluster. The velocity dispersion profiles of blue and red GCs show a quite distinct behaviour. Blue GCs exhibit a sharp increase in the velocity dispersion profile from 250 to 400km/s within 5 arcminutes (~29kpc~1r_eff_ of NGC 1399) from the central galaxy. The velocity dispersion profile of red GCs follows a constant value between 200-300km/s until 8 arcminutes (~46kpc~1.6r_eff_, and then rises to 350km/s at 10 arcminutes (~58kpc~2r_eff_). Beyond 10 arcminutes and out to 40 arcminutes (~230kpc~8r_eff_), blue and red GCs show a constant velocity dispersion of 300+/-50km/s, indicating that both GC populations trace the cluster potential. We kinematically confirm and characterise the previously photometrically discovered overdensities of intra-cluster GCs. We found that these substructured intra-cluster regions in Fornax are dominated mostly by blue GCs.
We present a panoramic study of the Fornax dwarf spheroidal galaxy, using data obtained as part of the VLT Survey Telescope (VST) ATLAS Survey. The data presented here - a subset of the full survey - uniformly cover a region of 25deg^2^ centred on the galaxy, in g, r and i bands. This large area coverage reveals two key differences to previous studies of Fornax. First, data extending beyond the nominal tidal radius of the dwarf highlight the presence of a second distinct red giant branch population. This bluer red giant branch appears to be co-eval with the horizontal branch population. Secondly, a shell structure located approximately 1.4{deg} from the centre of Fornax is shown to be a mis-identified background overdensity of galaxies. This last result casts further doubt on the hypothesis that Fornax underwent a gas-rich merger in its relatively recent past.
We present low resolution multi-object spectroscopy of an I-band magnitude limited (I_AB_~23-23.5) sample of galaxies located in an area centered on the Hubble Deep Field-South (HDFS). The observations were obtained using the Focal Reducer/low dispersion Spectrograph (FORS) on the ESO Very Large Telescope. Thirty-two primary spectroscopic targets in the HST-WFPC2 HDFS were supplemented with galaxies detected in the Infrared Space Observatory's survey of the HDFS and the ESO Imaging Deep Survey to comprise a sample of 100 galaxies for spectroscopic observations. Based on detections of several emission lines, such as [OII]3727, H{beta} and [OIII]5007, or of other spectroscopic features, we measured accurate redshifts for 50 objects in the central HDFS and flanking fields. The redshift range of the current sample of galaxies is 0.6-1.2, with a median redshift of 1.13 (at I~23.5 not corrected for completeness). The sample is dominated by starburst galaxies with only a small fraction of ellipticals (~10%). For the emission line objects, the extinction corrected [OII]3727 line strengths yield estimates of star formation rates in the range 0.5-30M_{sun}_/yr. We used the present data to derive the [OII]3727 luminosity function up to redshift of 1.2. When combined with [OII]3727 luminosity densities for the local and high redshift Universe, our results confirm the steep rise in the star formation rate (SFR) to z~1.3.
The Foundation Supernova Survey aims to provide a large, high-fidelity, homogeneous, and precisely calibrated low-redshift Type Ia supernova (SN Ia) sample for cosmology. The calibration of the current low-redshift SN sample is the largest component of systematic uncertainties for SN cosmology, and new data are necessary to make progress. We present the motivation, survey design, observation strategy, implementation, and first results for the Foundation Supernova Survey. We are using the Pan-STARRS telescope to obtain photometry for up to 800 SNe Ia at z<~0.1. This strategy has several unique advantages: (1) the Pan-STARRS system is a superbly calibrated telescopic system, (2) Pan-STARRS has observed 3/4 of the sky in grizyP1 making future template observations unnecessary, (3) we have a well-tested data-reduction pipeline, and (4) we have observed ~3000 high-redshift SNe Ia on this system. Here, we present our initial sample of 225 SN Ia grizP1 light curves, of which 180 pass all criteria for inclusion in a cosmological sample. The Foundation Supernova Survey already contains more cosmologically useful SNe Ia than all other published low-redshift SN Ia samples combined. We expect that the systematic uncertainties for the Foundation Supernova Sample will be two to three times smaller than other low-redshift samples. We find that our cosmologically useful sample has an intrinsic scatter of 0.111mag, smaller than other low-redshift samples. We perform detailed simulations showing that simply replacing the current low-redshift SN Ia sample with an equally sized Foundation sample will improve the precision on the dark energy equation-of-state parameter by 35 per cent, and the dark energy figure of merit by 72 per cent.
Four new eclipsing mid M-dwarf systems from MEarth
Short Name:
J/AJ/156/140
Date:
21 Oct 2021
Publisher:
CDS
Description:
Using data from the MEarth-North and MEarth-South transit surveys, we present the detection of eclipses in four mid M-dwarf systems: LP 107-25, LP 261-75, LP 796-24, and LP 991-15. Combining the MEarth photometry with spectroscopic follow-up observations, we show that LP 107-25 and LP 796-24 are short-period (1.388 and 0.523 day, respectively) eclipsing binaries in triple-lined systems with substantial third-light contamination from distant companions. LP 261-75 is a short-period (1.882 day) single-lined system consisting of a mid M-dwarf eclipsed by a probable brown dwarf secondary, with another distant visual brown dwarf companion. LP 991-15 is a long-period (29.3 day) double-lined eclipsing binary on an eccentric orbit with a geometry that produces only primary eclipses. A spectroscopic orbit is given for LP 991-15, and initial orbits for LP 107-25 and LP 261-75.
SN 2013dy is a Type Ia supernova (SN Ia) for which we have compiled an extraordinary data set spanning from 0.1 to ~500d after explosion. We present 10 epochs of ultraviolet (UV) through near-infrared (NIR) spectra with Hubble Space Telescope/Space Telescope Imaging Spectrograph, 47 epochs of optical spectra (15 of them having high resolution), and more than 500 photometric observations in the BVrRiIZYJH bands. SN 2013dy has a broad and slowly declining light curve ({Delta}m_15_(B)=0.92mag), shallow SiII {lambda}6355 absorption, and a low velocity gradient. We detect strong CII in our earliest spectra, probing unburned progenitor material in the outermost layers of the SN ejecta, but this feature fades within a few days. The UV continuum of SN 2013dy, which is strongly affected by the metal abundance of the progenitor star, suggests that SN 2013dy had a relatively high-metallicity progenitor. Examining one of the largest single set of high-resolution spectra for an SN Ia, we find no evidence of variable absorption from circumstellar material. Combining our UV spectra, NIR photometry, and high-cadence optical photometry, we construct a bolometric light curve, showing that SN 2013dy had a maximum luminosity of 10.0^+4.8^_-3.8_x10^42^erg/s. We compare the synthetic light curves and spectra of several models to SN 2013dy, finding that SN 2013dy is in good agreement with a solar-metallicity W7 model.
We describe the properties of the 3838 galaxies that were monitored for SNe events, including newly determined morphologies and their DENIS and POSS-II/UKST I, 2MASS and DENIS J and K_s_ and 2MASS H magnitudes. We have compared 2MASS, DENIS and POSS-II/UKST IJK magnitudes in order to find possible systematic photometric shifts in the measurements. The DENIS and POSS-II/UKST I band magnitudes show large discrepancies (mean absolute difference of 0.4mag), mostly due to different spectral responses of the two instruments, with an important contribution (0.33mag rms) from the large uncertainties in the photometric calibration of the POSS-II and UKST photographic plates. In the other wavebands, the limiting near infrared magnitude, morphology, and inclination of the galaxies are the most influential factors which affect the determination of photometry of the galaxies. Nevertheless, no significant systematic differences have been found between of any pair of NIR magnitude measurements, except for a few percent of galaxies showing large discrepancies. This allows us to combine DENIS and 2MASS data for the J and K_s_ filters.
We present UV luminosity functions of dropout galaxies at z~6-10 with the complete Hubble Frontier Fields data. We obtain a catalog of ~450 dropout-galaxy candidates (350, 66, and 40 at z~6-7, 8, and 9, respectively), with UV absolute magnitudes that reach ~-14mag, ~2 mag deeper than the Hubble Ultra Deep Field detection limits. We carefully evaluate number densities of the dropout galaxies by Monte Carlo simulations, including all lensing effects such as magnification, distortion, and multiplication of images as well as detection completeness and contamination effects in a self-consistent manner. We find that UV luminosity functions at z~6-8 have steep faint-end slopes, {alpha}~-2, and likely steeper slopes, {alpha}<~-2 at z~9-10. We also find that the evolution of UV luminosity densities shows a non-accelerated decline beyond z~8 in the case of M_trunc_=-15, but an accelerated one in the case of M_trunc_=-17. We examine whether our results are consistent with the Thomson scattering optical depth from the Planck satellite and the ionized hydrogen fraction Q_HII_ at z<~7 based on the standard analytic reionization model. We find that reionization scenarios exist that consistently explain all of the observational measurements with the allowed parameters of f_esc_=0.17_-0.03_^+0.07^ and M_trunc_>-14.0 for log{xi}_ion_/[erg^-1^Hz]=25.34, where f_esc_ is the escape fraction, Mtrunc is the faint limit of the UV luminosity function, and {xi}_ion_ is the conversion factor of the UV luminosity to the ionizing photon emission rate. The length of the reionization period is estimated to be {Delta}z=3.9_-1.6_^+2.0^ (for 0.1<Q_HII_<0.99), consistent with the recent estimate from Planck.
We present the results of SPT-GMOS, a spectroscopic survey with the Gemini Multi-Object Spectrograph (GMOS) on Gemini South. The targets of SPT-GMOS are galaxy clusters identified in the SPT-SZ survey, a millimeter-wave survey of 2500deg^2^ of the southern sky using the South Pole Telescope (SPT). Multi-object spectroscopic observations of 62 SPT-selected galaxy clusters were performed between 2011 January and 2015 December, yielding spectra with radial velocity measurements for 2595 sources. We identify 2243 of these sources as galaxies, and 352 as stars. Of the galaxies, we identify 1579 as members of SPT-SZ galaxy clusters. The primary goal of these observations was to obtain spectra of cluster member galaxies to estimate cluster redshifts and velocity dispersions. We describe the full spectroscopic data set and resulting data products, including galaxy redshifts, cluster redshifts, and velocity dispersions, and measurements of several well-known spectral indices for each galaxy: the equivalent width, W, of [OII]{lambda}{lambda}3727, 3729 and H-{delta}, and the 4000{AA} break strength, D4000. We use the spectral indices to classify galaxies by spectral type (i.e., passive, post-starburst, star-forming), and we match the spectra against photometric catalogs to characterize spectroscopically observed cluster members as a function of brightness (relative to m*). Finally, we report several new measurements of redshifts for ten bright, strongly lensed background galaxies in the cores of eight galaxy clusters. Combining the SPT-GMOS data set with previous spectroscopic follow-up of SPT-SZ galaxy clusters results in spectroscopic measurements for >100 clusters, or ~20% of the full SPT-SZ sample.
