- ID:
- ivo://CDS.VizieR/J/ApJ/840/30
- Title:
- HST/Gemini proper motions for Pyxis
- Short Name:
- J/ApJ/840/30
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a proper motion measurement for the halo globular cluster Pyxis, using Hubble Space Telescope/ACS data as the first epoch and GeMS/GSAOI Adaptive Optics data as the second, separated by a baseline of ~5 years. This is both the first measurement of the proper motion of Pyxis and the first calibration and use of Multi-Conjugate Adaptive Optics data to measure an absolute proper motion for a faint, distant halo object. Consequently, we present our analysis of the Adaptive Optics data in detail. We obtain a proper motion of {mu}_{alpha}_cos({delta})=1.09+/-0.31mas/yr and {mu}_{delta}_=0.68+/-0.29mas/yr. From the proper motion and line-of-sight velocity, we find that the orbit of Pyxis is rather eccentric, with its apocenter at more than 100kpc and its pericenter at about 30kpc. We also investigate two literature-proposed associations for Pyxis with the recently discovered ATLAS stream and the Magellanic system. Combining our measurements with dynamical modeling and cosmological numerical simulations, we find it unlikely Pyxis is associated with either system. We examine other Milky Way satellites for possible association using the orbit, eccentricity, metallicity, and age as constraints and find no likely matches in satellites down to the mass of Leo II. We propose that Pyxis probably originated in an unknown galaxy, which today is fully disrupted. Assuming that Pyxis is bound and not on a first approach, we derive a 68% lower limit on the mass of the Milky Way of 0.95x10^12^M_{sun}_.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/586/765
- Title:
- HST K-selected extremely red galaxies
- Short Name:
- J/ApJ/586/765
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We selected 115 extremely red objects (EROs) from deep Hubble Space Telescope (HST) WFPC2 archive data combined with ground-based K-band images, with (F814W-Ks)>=4, K-band signal-to-noise ratio >=5, and a median limiting Ks magnitude of ~18.7, over a corresponding area of 228 arcmin2, for a morphological study of the ERO galaxy population. The survey covered a total of ~409-arcmin^2^ over 77 separate WFPC2 fields. This is the first complete sample of bright EROs with high-resolution HST morphologies.
- ID:
- ivo://CDS.VizieR/J/ApJ/716/712
- Title:
- HST light curves of six SNe and Union2
- Short Name:
- J/ApJ/716/712
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on work to increase the number of well-measured Type Ia supernovae (SNe Ia) at high redshifts. Light curves, including high signal-to-noise Hubble Space Telescope data, and spectra of six SNe Ia that were discovered during 2001, are presented. Additionally, for the two SNe with z>1, we present ground-based J-band photometry from Gemini and the Very Large Telescope. These are among the most distant SNe Ia for which ground-based near-IR observations have been obtained. We add these six SNe Ia together with other data sets that have recently become available in the literature to the Union compilation. We have made a number of refinements to the Union analysis chain, the most important ones being the refitting of all light curves with the SALT2 fitter and an improved handling of systematic errors. We call this new compilation, consisting of 557 SNe, the Union2 compilation.
- ID:
- ivo://CDS.VizieR/J/MNRAS/330/1
- Title:
- HST observations of Extremely Red Objects
- Short Name:
- J/MNRAS/330/1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a survey for extremely red objects (EROs) undertaken in the fields of 10 massive galaxy cluster lenses at z~0.2, combining sensitive, high-resolution Hubble Space Telescope imaging with deep, half-arcsecond K-band imaging from UKIRT. We detect 60 EROs with (R-K)>=5.3, of which 26 have (R-K)>=6.0 in a total image-plane survey area of 49arcmin2 down to K=20.6, including one multiply imaged ERO.
- ID:
- ivo://CDS.VizieR/J/ApJ/541/977
- Title:
- HST observations of low-mass stars in IC 348
- Short Name:
- J/ApJ/541/977
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the low-mass population of the young cluster IC 348 down to the deuterium-burning limit, a fiducial boundary between brown dwarf and planetary mass objects, using a new and innovative method for the spectral classification of late-type objects. Using photometric indices, constructed from HST/NICMOS narrowband imaging, that measure the strength of the 1.9{mu}m water band, we determine the spectral type and reddening for every M-type star in the field, thereby separating cluster members from the interloper population. Due to the efficiency of our spectral classification technique, our study is complete from ~0.7 to 0.015M_{sun}_. The mass function derived for the cluster in this interval, dN/dlogM{prop.to}M^0.5^, is similar to that obtained for the Pleiades, but appears significantly more abundant in brown dwarfs than the mass function for companions to nearby Sunlike stars. This provides compelling observational evidence for different formation and evolutionary histories for substellar objects formed in isolation versus as companions. Because our determination of the IMF is complete to very low masses, we can place interesting constraints on the role of physical processes such as fragmentation in the star and planet formation process and the fraction of dark matter in the Galactic halo that resides in substellar objects.
- ID:
- ivo://CDS.VizieR/J/ApJ/886/99
- Title:
- HST obs. in the region of 3 young LMC SNIa remnants
- Short Name:
- J/ApJ/886/99
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have used two methods to search for surviving companions of Type Ia supernova progenitors in three Balmer-dominated supernova remnants in the Large Magellanic Cloud: 0519-69.0, 0505-67.9 (DEM L71), and 0548-70.4. In the first method, we use the Hubble Space Telescope photometric measurements of stars to construct color-magnitude diagrams (CMDs) and compare positions of stars in the CMDs with those expected from theoretical post-impact evolution of surviving main-sequence or helium star companions. No obvious candidates of surviving companions are identified in this photometric search. Future models for surviving red giant companions or with different explosion mechanisms are needed for thorough comparisons with these observations in order to make more definitive conclusions. In the second method, we use Multi Unit Spectroscopic Explorer observations of 0519-69.0 and DEM L71 to carry out spectroscopic analyses of stars in order to use large peculiar radial velocities as diagnostics of surviving companions. We find a star in 0519-69.0 and a star in DEM L71 moving at radial velocities of 182+/-0km/s and 213+/-0km/s, respectively, more than 2.5{sigma} from the mean radial velocity of the underlying stellar population, 264 and 270km/s, respectively. These stars need higher-quality spectra to investigate their abundances and rotation velocities to determine whether they are indeed surviving companions of the supernova progenitors.
- ID:
- ivo://CDS.VizieR/J/ApJ/857/67
- Title:
- HST obs. of Mira candidates in NGC 4258
- Short Name:
- J/ApJ/857/67
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present year-long, near-infrared (NIR) Hubble Space Telescope (HST) WFC3 observations of Mira variables in the water megamaser host galaxy NGC 4258. Miras are asymptotic giant branch variables that can be divided into oxygen- (O-) and carbon- (C-) rich subclasses. Oxygen-rich Miras follow a tight (scatter ~0.14mag) period-luminosity relation (PLR) in the NIR and can be used to measure extragalactic distances. The water megamaser in NGC 4258 gives a geometric distance to the galaxy accurate to 2.6% that can serve to calibrate the Mira PLR. We develop criteria for detecting and classifying O-rich Miras with optical and NIR data as well as NIR data alone. In total, we discover 438 Mira candidates that we classify with high confidence as O-rich. Our most stringent criteria produce a sample of 139 Mira candidates that we use to measure a PLR. We use the OGLE-III sample of O-rich Miras in the Large Magellanic Cloud to obtain a relative distance modulus, {mu}_4258_-{mu}_LMC_=10.95+/-0.01 (statistical) +/-0.06 (systematic) mag, that is statistically consistent with the relative distance determined using Cepheids. These results demonstrate the feasibility of discovering and characterizing Miras using the NIR with the HST and the upcoming James Webb Space Telescope and using those Miras to measure extragalactic distances and determine the Hubble constant.
- ID:
- ivo://CDS.VizieR/J/ApJ/889/5
- Title:
- HST obs. of Mira variables in the SNIa host NGC1559
- Short Name:
- J/ApJ/889/5
- Date:
- 17 Jan 2022 11:46:55
- Publisher:
- CDS
- Description:
- We present year-long, near-infrared Hubble Space Telescope (HST) WFC3 observations used to search for Mira variables in NGC 1559, the host galaxy of the Type Ia supernova (SN Ia) SN 2005df. This is the first dedicated search for Miras, highly evolved low-mass stars, in an SNIa host, and subsequently the first calibration of the SN Ia luminosity using Miras in a role historically played by Cepheids. We identify a sample of 115 O-rich Miras with P<400days based on their light-curve properties. We find that the scatter in the Mira period-luminosity relation (PLR) is comparable to Cepheid PLRs seen in SN Ia host galaxies. Using a sample of O-rich Miras discovered in NGC 4258 with HSTF160W and its maser distance, we measure a distance modulus for NGC1559 of {mu}_1559_=31.41+/-0.050(statistical)+/-0.060(systematic)mag. Based on the light curve of the normal, well-observed, low-reddening SN 2005df, we obtain a measurement of the fiducial SN Ia absolute magnitude of M_B_^0^=-19.27+/-0.13mag. With the Hubble diagram of SNe Ia we find H_0_=72.7+/-4.6km/s/Mpc. Combining the calibration from the NGC 4258 megamaser and the Large Magellanic Cloud detached eclipsing binaries gives a best value of H_0_=73.3+/-4.0km/s/Mpc. This result is within 1{sigma} of the Hubble constant derived using Cepheids and multiple calibrating SNe Ia. This is the first of four expected calibrations of the SN Ia luminosity from Miras that should reduce the error in H_0_ via Miras to ~3%. In light of the present Hubble tension and JWST, Miras have utility in the extragalactic distance scale to check Cepheid distances or calibrate nearby SNe in early-type host galaxies that would be unlikely targets for Cepheid searches.
- ID:
- ivo://CDS.VizieR/J/ApJ/902/26
- Title:
- HST opt. & H-band obs. of Cepheids in NGC4151
- Short Name:
- J/ApJ/902/26
- Date:
- 14 Mar 2022 07:44:50
- Publisher:
- CDS
- Description:
- We derive a distance of 15.8+/-0.4Mpc to the archetypal Seyfert 1 galaxy NGC 4151 based on the near-infrared Cepheid period-luminosity relation and new Hubble Space Telescope multiband imaging. This distance determination, based on measurements of 35 long-period (P>25d) Cepheids, will support the absolute calibration of the supermassive black hole mass in this system, as well as studies of the dynamics of the feedback or feeding of its active galactic nucleus.
800. HST photometry of M4
- ID:
- ivo://CDS.VizieR/J/ApJS/120/265
- Title:
- HST photometry of M4
- Short Name:
- J/ApJS/120/265
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper presents a detailed description of the acquisition and processing of a large body of imaging data for three fields in the globular cluster M4 taken with the Wide Field and Planetary Camera 2 aboard the Hubble Space Telescope. Analysis with the ALLFRAME package yielded the deepest photometry yet obtained for this cluster. The resulting data set for 4708 stars (positions and calibrated photometry in V, I, and, in two fields, U) spanning approximately six cluster core radii is presented. The scientific analysis is deferred to three companion papers, which investigate the significant white dwarf population discovered and the main-sequence population.
