- ID:
- ivo://CDS.VizieR/J/AJ/162/101
- Title:
- K2 ugri & H{alpha} photometry in the Lagoon Nebula
- Short Name:
- J/AJ/162/101
- Date:
- 14 Mar 2022 06:42:13
- Publisher:
- CDS
- Description:
- Space observatories have provided unprecedented depictions of the many variability behaviors typical of low-mass, young stars. However, those studies have so far largely omitted more massive objects (~2M{sun} to 4-5M{sun}) and were limited by the absence of simultaneous, multiwavelength information. We present a new study of young star variability in the ~1-2Myr old, massive Lagoon Nebula region. Our sample encompasses 278 young, late B to K-type stars, monitored with Kepler/K2. Auxiliary u, g, r, i, H{alpha} time-series photometry, simultaneous with K2, was acquired at the Paranal Observatory. We employed this comprehensive data set and archival infrared photometry to determine individual stellar parameters, assess the presence of circumstellar disks, and tie the variability behaviors to inner disk dynamics. We found significant mass-dependent trends in variability properties, with B/A stars displaying substantially reduced levels of variability compared to G/K stars for any light-curve morphology. These properties suggest different magnetic field structures at the surface of early-type and later-type stars. We also detected a dearth of some disk-driven variability behaviors, particularly dippers, among stars earlier than G. This indicates that their higher surface temperatures and more chaotic magnetic fields prevent the formation and survival of inner disk dust structures corotating with the star. Finally, we examined the characteristic variability timescales within each light curve and determined that the day-to-week timescales are predominant over the K2 time series. These reflect distinct processes and locations in the inner disk environment, from intense accretion triggered by instabilities in the innermost disk regions to variable accretion efficiency in the outer magnetosphere.
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- ID:
- ivo://CDS.VizieR/J/PAZh/25/276
- Title:
- KV Cyg, V435 Cyg, V699 Cyg UBVR photometry
- Short Name:
- J/PAZh/25/276
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The results of a UBVR photometry observations are presented for eclipsing binaries KV Cyg, V435 Cyg and V699 Cyg. Each binary was observed 1989/91 with the 60 cm telescopes at Maidanak Observatory (Uzbekistan).
- ID:
- ivo://CDS.VizieR/J/ApJS/234/5
- Title:
- LaCoSSPAr in the Southern Galactic Cap. I.
- Short Name:
- J/ApJS/234/5
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a spectroscopic redshift catalog from the LAMOST Complete Spectroscopic Survey of Pointing Area (LaCoSSPAr) in the Southern Galactic Cap (SGC), which is designed to observe all sources (Galactic and extragalactic) by using repeating observations with a limiting magnitude of r=18.1mag in two 20deg^2^ fields. The project is mainly focusing on the completeness of LAMOST ExtraGAlactic Surveys (LEGAS) in the SGC, the deficiencies of source selection methods, and the basic performance parameters of the LAMOST telescope. In both fields, more than 95% of galaxies have been observed. A post-processing has been applied to the LAMOST 1D spectrum to remove the majority of remaining sky background residuals. More than 10000 spectra have been visually inspected to measure the redshift by using combinations of different emission/absorption features with an uncertainty of {sigma}_z_/(1+z)<0.001. In total, 1528 redshifts (623 absorption and 905 emission line galaxies) in Field A and 1570 redshifts (569 absorption and 1001 emission line galaxies) in Field B have been measured. The results show that it is possible to derive redshift from low S/N galaxies with our post-processing and visual inspection. Our analysis also indicates that up to one-fourth of the input targets for a typical extragalactic spectroscopic survey might be unreliable. The multi-wavelength data analysis shows that the majority of mid-infrared-detected absorption (91.3%) and emission line galaxies (93.3%) can be well separated by an empirical criterion of W2-W3=2.4. Meanwhile, a fainter sequence paralleled to the main population of galaxies has been witnessed both in Mr/W2-W3 and M*/W2-W3 diagrams, which could be the population of luminous dwarf galaxies but contaminated by the edge-on/highly inclined galaxies (~30%).
- ID:
- ivo://CDS.VizieR/J/ApJ/863/92
- Title:
- LAE cand. at z~5.7 in the field of QSO J0148+0600
- Short Name:
- J/ApJ/863/92
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The observed scatter in intergalactic Ly{alpha} opacity at z<~6 requires large-scale fluctuations in the neutral fraction of the intergalactic medium (IGM) after the expected end of reionization. Post-reionization models that explain this scatter invoke fluctuations in either the ionizing ultraviolet background (UVB) or IGM temperature. These models make very different predictions, however, for the relationship between Ly{alpha} opacity and local density. Here, we test these models using Ly{alpha}-emitting galaxies (LAEs) to trace the density field surrounding the longest and most opaque known Ly{alpha} trough at z<6. Using deep Subaru Hyper Suprime-Cam narrowband imaging, we find a highly significant deficit of z~5.7 LAEs within 20h^-1^Mpc of the trough. The results are consistent with a model in which the scatter in Ly{alpha} opacity near z~6 is driven by large-scale UVB fluctuations, and disfavor a scenario in which the scatter is primarily driven by variations in IGM temperature. UVB fluctuations at this epoch present a boundary condition for reionization models, and may help shed light on the nature of the ionizing sources.
- ID:
- ivo://CDS.VizieR/J/ApJ/744/110
- Title:
- LAE galaxies between 2.1=<z<=3.1
- Short Name:
- J/ApJ/744/110
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We describe the results of a new, wide-field survey for z=3.1 Ly{alpha} emitters (LAEs) in the Extended Chandra Deep Field South (ECDF-S). By using a nearly top-hat 5010{AA} filter and complementary broadband photometry from the MUSYC survey, we identify a complete sample of 141 objects with monochromatic fluxes brighter than 2.4x10^-17^erg/cm^2^/s and observers-frame equivalent widths (EWs) greater than ~80{AA} (i.e., 20{AA} in the rest frame of Ly{alpha}). The bright end of this data set is dominated by X-ray sources and foreground objects with Galaxy Evolution Explorer detections, but when these interlopers are removed, we are still left with a sample of 130 LAE candidates, 39 of which have spectroscopic confirmations. This sample overlaps the set of objects found in an earlier ECDF-S survey, but due to our filter's redder bandpass, it also includes 68 previously uncataloged sources. We confirm earlier measurements of the z=3.1 LAE emission-line luminosity function and show that an apparent anticorrelation between EW and continuum brightness is likely due to the effect of correlated errors in our heteroskedastic data set. Finally, we compare the properties of z=3.1 LAEs to LAEs found at z=2.1. We show that in the ~1Gyr after z~3, the LAE luminosity function evolved significantly, with L* fading by ~0.4mag, the number density of sources with L>1.5x10^42^erg/s declining by ~50%, and the EW scale length contracting from 70^+7^_-5_{AA} to 50^+9^_-6_{AA}. When combined with literature results, our observations demonstrate that over the redshift range z~0 to z~4, LAEs contain less than ~10% of the star formation rate density of the universe.
- ID:
- ivo://CDS.VizieR/J/ApJ/753/95
- Title:
- LAE galaxies in the ECDF-S at z~2.1 and z~3.1
- Short Name:
- J/ApJ/753/95
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a rest-frame ultraviolet morphological analysis of 108 z~2.1 Ly{alpha} emitters (LAEs) in the Extended Chandra Deep Field South and compare it to a similar sample of 171 LAEs at z~3.1. Using Hubble Space Telescope images from the Galaxy Evolution from Morphology and SEDs survey, Great Observatories Origins Deep Survey, and Hubble Ultradeep Field, we measure size and photometric component distributions, where photometric components are defined as distinct clumps of UV-continuum emission. At both redshifts, >80% of LAEs have observed half-light radii <2kpc, but the median half-light radius rises from 0.95+/-0.04kpc at z=3.1 to 1.41+/-0.14kpc at z=2.1. A similar evolution is seen in the sizes of individual rest-UV components, but there is no evidence for evolution in the number of multi-component systems. In the z=2.1 sample, we see clear correlations between the size of an LAE and other physical properties derived from its spectral energy distribution (SED). LAEs are found to be larger for galaxies with higher stellar mass, star formation rate, and dust obscuration, but there is no evidence for a trend between equivalent width and half-light radius at either redshift. The presence of these correlations suggests that a wide range of objects are being selected by LAE surveys at z~2, including a significant fraction of objects for which a massive and moderately extended population of old stars underlies the young starburst giving rise to the Ly{alpha} emission.
- ID:
- ivo://CDS.VizieR/J/ApJ/865/L1
- Title:
- LAEs discovered with ultra-deep MUSE sp. in UDF
- Short Name:
- J/ApJ/865/L1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using an ultra-deep blind survey with the MUSE integral field spectrograph on the European Southern Observatory Very Large Telescope, we obtain spectroscopic redshifts to a depth never before explored: galaxies with observed magnitudes m_AB_>~30-32. Specifically, we detect objects via Ly{alpha} emission at 2.9<z<6.7 without individual continuum counterparts in areas covered by the deepest optical/near-infrared imaging taken by the Hubble Space Telescope, the Hubble Ultra Deep Field. In total, we find 102 such objects in 9 square arcminutes at these redshifts. Detailed stacking analyses confirm the Ly{alpha} emission as well as the 1216 {AA} breaks and faint ultraviolet continua (M_UV_~-15). This makes them the faintest spectroscopically confirmed objects at these redshifts, similar to the sources believed to reionize the universe. A simple model for the expected fraction of detected/undetected Ly{alpha} emitters as a function of luminosity is consistent with these objects being the high-equivalent width tail of the normal Ly{alpha}-emitter population at these redshifts.
- ID:
- ivo://CDS.VizieR/J/ApJ/622/129
- Title:
- Lag-luminosity relationship in AGN
- Short Name:
- J/ApJ/622/129
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We determine interband lags between variations in the B band and variations in the V, R, and I bands for 14 active galactic nuclei observed at the Crimean Astrophysical Observatory. The computed lags range from tenths of a day to several days, and it is positive (that is, V, R, and I bands lag behind the B band) in most cases, except for a few cases for the V filter.
- ID:
- ivo://CDS.VizieR/J/MNRAS/453/1026
- Title:
- Lagoon Nebula M8 T tauri accretion rates
- Short Name:
- J/MNRAS/453/1026
- Date:
- 03 Nov 2021
- Publisher:
- CDS
- Description:
- We estimate the accretion rates of 235 Classical T Tauri star (CTTS) candidates in the Lagoon Nebula using ugri H{alpha} photometry from the VST Photometric H{alpha} survey+. Our sample consists of stars displaying H{alpha} excess, the intensity of which is used to derive accretion rates. For a subset of 87 stars, the intensity of the u-band excess is also used to estimate accretion rates. We find the mean variation in accretion rates measured using H{alpha} and u-band intensities to be ~0.17dex, agreeing with previous estimates (0.04-0.4dex) but for a much larger sample. The spatial distribution of CTTS align with the location of protostars and molecular gas suggesting that they retain an imprint of the natal gas fragmentation process. Strong accretors are concentrated spatially, while weak accretors are more distributed. Our results do not support the sequential star-forming processes suggested in the literature.
- ID:
- ivo://CDS.VizieR/J/ApJ/747/51
- Title:
- Lagoon Nebula stars. I. Rotation periods
- Short Name:
- J/ApJ/747/51
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have conducted a long-term, wide-field, high-cadence photometric monitoring survey of ~50000 stars in the Lagoon Nebula H II region. This first paper presents rotation periods for 290 low-mass stars in NGC 6530, the young cluster illuminating the nebula, and for which we assemble a catalog of infrared and spectroscopic disk indicators, estimated masses and ages, and X-ray luminosities. The distribution of rotation periods we measure is broadly uniform for 0.5days<P<10days; the short-period cutoff corresponds to breakup. We observe no obvious bimodality in the period distribution, but we do find that stars with disk signatures rotate more slowly on average. The stars' X-ray luminosities are roughly flat with rotation period, at the saturation level (log L_X_/L_bol_{approx} -3.3). However, we find a significant positive correlation between L_X_/L_bol_ and corotation radius, suggesting that the observed X-ray luminosities are regulated by centrifugal stripping of the stellar coronae. The period-mass relationship in NGC 6530 is broadly similar to that of the Orion Nebula Cluster (ONC), but the slope of the relationship among the slowest rotators differs from that in the ONC and other young clusters. We show that the slope of the period-mass relationship for the slowest rotators can be used as a proxy for the age of a young cluster, and we argue that NGC 6530 may be slightly younger than the ONC, making it a particularly important touchstone for models of angular momentum evolution in young, low-mass stars.
