- ID:
- ivo://CDS.VizieR/J/ApJ/869/123
- Title:
- Keck Lyman continuum spectroscopic survey (KLCS)
- Short Name:
- J/ApJ/869/123
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results of a deep spectroscopic survey quantifying the statistics of the escape of ionizing radiation from star-forming galaxies at z~3. We measure the ratio of ionizing to non-ionizing UV flux density <f_900_/f_1500_>_obs_, where f_900_ is the mean flux density evaluated over the range [880,910]{AA}. We quantify the emergent ratio of ionizing to non-ionizing UV flux density by analyzing high signal-to-noise ratio composite spectra formed from subsamples with common observed properties and numbers sufficient to reduce the statistical uncertainty in the modeled IGM+CGM correction to obtain precise values of <f_900_/f_1500_>_out_, including a full-sample average <f_900_/f_1500>_out_=0.057{+/-}0.006. We show that <f_900_/f_1500_>_out_ increases monotonically with W_{lambda}_(Ly{alpha}), inducing an inverse correlation with UV luminosity as a by-product. We fit the composite spectra using stellar spectral synthesis together with models of the ISM in which a fraction f_c_ of the stellar continuum is covered by gas with column density N_HI_. We show that the composite spectra simultaneously constrain the intrinsic properties of the stars (L_900_/L_1500_)_int_ along with f_c_, N_HI_, E(B-V), and f_esc,abs_, the absolute escape fraction of ionizing photons. We find a sample-averaged f_esc,abs_=0.09{+/-}0.01, with subsamples falling along a linear relation <f_esc,abs_>~0.75[W_{lambda}_(Ly{alpha})/110{AA}]. Using the far-UV luminosity function, the distribution function n(W(Ly{alpha})), and the relationship between W_{lambda}_(Ly{alpha}) and <f_900_/f_1500_>_out_, we estimate the total ionizing emissivity of z~3 star-forming galaxies with M_uv_<=-19.5, which exceeds the contribution of quasi-stellar objects by a factor of ~3, and accounts for ~50% of the total {epsilon}LyC at z~3 estimated using indirect methods.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/834/101
- Title:
- Keck/MOSFIRE spectroscopy of ZFOURGE galaxies
- Short Name:
- J/ApJ/834/101
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We compare galaxy scaling relations as a function of environment at z~2 with our ZFIRE survey where we have measured H{alpha} fluxes for 90 star-forming galaxies selected from a mass-limited (log(M_*_/M_{sun}_)>9) sample based on ZFOURGE. The cluster galaxies (37) are part of a confirmed system at z=2.095 and the field galaxies (53) are at 1.9<z<2.4; all are in the COSMOS legacy field. There is no statistical difference between H{alpha}-emitting cluster and field populations when comparing their star formation rate (SFR), stellar mass (M_*_), galaxy size (r_eff_), SFR surface density ({Sigma}(H{alpha}_star_)), and stellar age distributions. The only difference is that at fixed stellar mass, the H{alpha}-emitting cluster galaxies are log(r_eff_)~0.1 larger than in the field. Approximately 19% of the H{alpha} emitters in the cluster and 26% in the field are IR-luminous (L_IR_>2x10^11^L_{sun}_). Because the luminous IR galaxies in our combined sample are ~5 times more massive than the low-IR galaxies, their radii are ~70% larger. To track stellar growth, we separate galaxies into those that lie above, on, or below the H{alpha} star-forming main sequence (SFMS) using {Delta}SFR(M*)=+/-0.2dex. Galaxies above the SFMS (starbursts) tend to have higher H{alpha} SFR surface densities and younger light-weighted stellar ages than galaxies below the SFMS. Our results indicate that starbursts (+SFMS) in the cluster and field at z~2 are growing their stellar cores. Lastly, we compare to the (SFR-M*) relation from Rhapsody-G cluster simulations and find that the predicted slope is nominally consistent with the observations. However, the predicted cluster SFRs tend to be too low by a factor of ~2, which seems to be a common problem for simulations across environment.
- ID:
- ivo://CDS.VizieR/J/AJ/157/71
- Title:
- Keck/NIRC2 astrometry for GSC 6214-210 b
- Short Name:
- J/AJ/157/71
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Direct-imaging exoplanet surveys have discovered a class of 5-20 M_Jup_ substellar companions at separations >100 au from their host stars, which present a challenge to planet and star formation models. Detailed analysis of the orbital architecture of these systems can provide constraints on possible formation mechanisms, including the possibility that they were dynamically ejected onto a wide orbit. We present astrometry for the wide planetary-mass companion GSC 6214-210 b (240 au; ~14 M_Jup_) obtained using NIRC2 with adaptive optics at the Keck telescope over 10 years. Our measurements achieved astrometric uncertainties of ~1 mas per epoch. We determined a relative motion of 1.12+/-0.15 mas/yr (0.61+/-0.09 km/s), the first detection of orbital motion for this companion. We compute the minimum periastron for the companion due to our measured velocity vector and derive constraints on the orbital parameters through our modified implementation of the Orbits for the Impatient rejection sampling algorithm. We find that close periastron orbits, which could indicate that the companion was dynamically scattered, are present in our posterior but have low likelihoods. For all orbits in our posterior, we assess the detectability of close-in companions that could have scattered GSC 6214-210 b from a closer orbit, and find that most potential scatterers would have been detected in previous imaging. We conclude that formation at small orbital separation and subsequent dynamical scattering through interaction with another potential close-in object is an unlikely formation pathway for this companion. We also update stellar and substellar properties for the system using the new parallax from Gaia DR2 (Cat. I/345).
- ID:
- ivo://CDS.VizieR/J/ApJ/873/65
- Title:
- Keck/NIRC2 obs. of the Galactic Center
- Short Name:
- J/ApJ/873/65
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Precision measurements of the stars in short-period orbits around the supermassive black hole at the Galactic Center are now being used to constrain general relativistic effects, such as the gravitational redshift and periapse precession. One of the largest systematic uncertainties in the measured orbits has been errors in the astrometric reference frame, which is derived from seven infrared-bright stars associated with SiO masers that have extremely accurate radio positions, measured in the Sgr A*-rest frame. We have improved the astrometric reference frame within 14" of the Galactic Center by a factor of 2.5 in position and a factor of 5 in proper motion. In the new reference frame, Sgr A* is localized to within a position of 0.645mas and proper motion of 0.03mas/yr. We have removed a substantial rotation (2.25{deg} per decade), that was present in the previous less-accurate reference frame used to measure stellar orbits in the field. With our improved methods and continued monitoring of the masers, we predict that orbital precession predicted by general relativity will become detectable in the next ~5yr.
- ID:
- ivo://CDS.VizieR/J/ApJ/751/132
- Title:
- Keck observations of the Arches cluster
- Short Name:
- J/ApJ/751/132
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the first detection of the intrinsic velocity dispersion of the Arches cluster - a young (~2Myr), massive (10^4^M_{sun}_) starburst cluster located only 26pc in projection from the Galactic center. This was accomplished using proper motion measurements within the central 10"x10" of the cluster, obtained with the laser guide star adaptive optics system at Keck Observatory over a three-year time baseline (2006-2009). This uniform data set results in proper motion measurements that are improved by a factor ~5 over previous measurements from heterogeneous instruments. By careful, simultaneous accounting of the cluster and field contaminant distributions as well as the possible sources of measurement uncertainties, we estimate the internal velocity dispersion to be 0.15+/-0.01mas/yr, which corresponds to 5.4+/-0.4km/s at a distance of 8.4kpc. Collateral benefits of our data and analysis include: (1) cluster membership probabilities, which may be used to extract a clean-cluster sample for future photometric work; (2) a refined estimate of the bulk motion of the Arches cluster with respect to the field, which we find to be 172+/-15km/s, which is slightly slower than suggested by previous measurements using one epoch each with the Very Large Telescope and the Keck telescope; and (3) a velocity dispersion estimate for the field itself, which is likely dominated by the inner Galactic bulge and the nuclear disk.
- ID:
- ivo://CDS.VizieR/IV/34
- Title:
- K2 Ecliptic Plane Input Catalog (EPIC)
- Short Name:
- IV/34
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The K2 Mission (Howell+, 2014PASP..126..398H) uses the Kepler spacecraft to obtain high-precision photometry over ~80 day campaigns in the ecliptic plane. The Ecliptic Plane Input Catalog (EPIC) provides coordinates, photometry, and kinematics based on a federation of all-sky catalogs to support target selection and target management for the K2 mission.
- ID:
- ivo://CDS.VizieR/J/ApJ/799/105
- Title:
- KELT light curve of the M82 SN 2014J
- Short Name:
- J/ApJ/799/105
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report observations of the bright M82 supernova 2014J serendipitously obtained with the Kilodegree Extremely Little Telescope (KELT). The supernova (SN) was observed at high cadence for over 100 days, from pre-explosion, to early rise and peak times, through the secondary bump. The high cadence KELT data with high signal-to-noise ratio is completely unique for SN 2014J and for any other SNIa, with the exception of the (yet) unpublished Kepler data. Here, we report determinations of the SN explosion time and peak time. We also report measures of the "smoothness" of the light curve on timescales of minutes/hours never before probed, and we use this to place limits on energy produced from short-lived isotopes or inhomogeneities in the explosion or the circumstellar medium. From the non-observation of significant perturbations of the light curves, we derive a 3{sigma} upper limit corresponding to 8.7x10^36^erg/s for any such extra sources of luminosity at optical wavelengths.
- ID:
- ivo://CDS.VizieR/J/ApJ/761/123
- Title:
- KELT-1 photometry and spectroscopy follow-up
- Short Name:
- J/ApJ/761/123
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the discovery of KELT-1b, the first transiting low-mass companion from the wide-field Kilodegree Extremely Little Telescope-North (KELT-North) transit survey. A joint analysis of the spectroscopic, radial velocity, and photometric data indicates that the V=10.7 primary is a mildly evolved mid-F star with T_eff_=6516+/-49K, logg=4.228^+0.014^_-0.021_, and [Fe/H]=0.052+/-0.079, with an inferred mass M_*_=1.335+/-0.063M_{sun}_ and radius R_*_=1.471^+0.045^_-0.035_R_{sun}_. The companion is a low-mass brown dwarf or a super-massive planet with mass M_P_=27.38+/-0.93M_Jup_ and radius R_P_=1.116^+0.038^_-0.029_R_Jup_. The companion is on a very short (~29 hr) period circular orbit, with an ephemeris T_c_ (BJD_TDB_)=2455909.29280+/-0.00023 and P=1.217501+/-0.000018 days. KELT-1b receives a large amount of stellar insolation, resulting in an estimated equilibrium temperature assuming zero albedo and perfect redistribution of T_eq_=2423^+34^_-27_K. Comparison with standard evolutionary models suggests that the radius of KELT-1b is likely to be significantly inflated. Adaptive optics imaging reveals a candidate stellar companion to KELT-1 with a separation of 588+/-1mas, which is consistent with an M dwarf if it is at the same distance as the primary. Rossiter-McLaughlin measurements during transit imply a projected spin-orbit alignment angle {lambda}=2+/-16deg, consistent with a zero obliquity for KELT-1. Finally, the vsinI_*_=56+/-2km/s of the primary is consistent at ~2{sigma} with tidal synchronization. Given the extreme parameters of the KELT-1 system, we expect it to provide an important testbed for theories of the emplacement and evolution of short-period companions, as well as theories of tidal dissipation and irradiated brown dwarf atmospheres.
- ID:
- ivo://CDS.VizieR/J/AJ/150/32
- Title:
- KELT 2006-2013 photometry of V409 Tau and AA Tau
- Short Name:
- J/AJ/150/32
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- AA Tau is a well studied young stellar object (YSO) that presents many of the photometric characteristics of a Classical T Tauri star (CTTS), including short-timescale stochastic variability attributed to spots and/or accretion as well as long-duration dimming events attributed to occultations by vertical features (e.g., warps) in its circumstellar disk. We present new photometric observations of AA Tau from the Kilodegree Extremely Little Telescope North (KELT-North) which reveal a deep, extended dimming event in 2011, which we show supports the interpretation by Bouvier et al. of an occultation by a high-density feature in the circumstellar disk located >8AU from the star. We also present KELT-North observations of V409 Tau, a relatively unstudied YSO also in Taurus-Auriga, showing short timescale erratic variability, along with two separate long and deep dimming events, one from 2009 January through late 2010 October, and the other from 2012 March until at least 2013 September. We interpret both dimming events to have lasted more than 600 days, each with a depth of ~1.4mag. From a spectral energy distribution analysis, we propose that V409 Tau is most likely surrounded by a circumstellar disk viewed nearly edge-on, and using Keplerian timescale arguments we interpret the deep dimmings of V409 Tau as occultations from one or more features within this disk >~10AU from the star. In both AA Tau and V409 Tau, the usual CTTS short-timescale variations associated with accretion processes close to the stars continue during the occultations, further supporting the distant occulting material interpretation. Like AA Tau, V409 Tau serves as a laboratory for studying the detailed structure of the protoplanetary environments of T Tauri disks, specifically disk structures that may be signposts of planet formation at many AU out in the disk. We also provide a table of all currently known disk-occulting young stars as a convenient reference for future work on such objects.
- ID:
- ivo://CDS.VizieR/J/AJ/156/234
- Title:
- KELT transit false positive catalog for TESS
- Short Name:
- J/AJ/156/234
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Kilodegree Extremely Little Telescope (KELT) project has been conducting a photometric survey of transiting planets orbiting bright stars for over 10 years. The KELT images have a pixel scale of ~23"/pixel very similar to that of NASA's Transiting Exoplanet Survey Satellite (TESS) - as well as a large point-spread function, and the KELT reduction pipeline uses a weighted photometric aperture with radius 3'. At this angular scale, multiple stars are typically blended in the photometric apertures. In order to identify false positives and confirm transiting exoplanets, we have assembled a follow-up network (KELT-FUN) to conduct imaging with spatial resolution, cadence, and photometric precision higher than the KELT telescopes, as well as spectroscopic observations of the candidate host stars. The KELT-FUN team has followed-up over 1600 planet candidates since 2011, resulting in more than 20 planet discoveries. Excluding ~450 false alarms of non-astrophysical origin (i.e., instrumental noise or systematics), we present an all-sky catalog of the 1128 bright stars (6<V<13) that show transit-like features in the KELT light curves, but which were subsequently determined to be astrophysical false positives (FPs) after photometric and/or spectroscopic follow-up observations. The KELT-FUN team continues to pursue KELT and other planet candidates and will eventually follow up certain classes of TESS candidates. The KELT FP catalog will help minimize the duplication of follow-up observations by current and future transit surveys such as TESS.
