- ID:
- ivo://CDS.VizieR/J/ApJ/768/102
- Title:
- I-band GALFIT analysis of luminous infrared galaxies
- Short Name:
- J/ApJ/768/102
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A Hubble Space Telescope/Advanced Camera for Surveys study of the structural properties of 85 luminous and ultraluminous (L_IR_>10^11.4^ L_{sun}_) infrared galaxies (LIRGs and ULIRGs) in the Great Observatories All-sky LIRG Survey (GOALS) sample is presented. Two-dimensional GALFIT analysis has been performed on F814W "I-band" images to decompose each galaxy, as appropriate, into bulge, disk, central point-spread function (PSF) and stellar bar components. The fraction of bulge-less disk systems is observed to be higher in LIRGs (35%) than in ULIRGs (20%), with the disk+bulge systems making up the dominant fraction of both LIRGs (55%) and ULIRGs (45%). Further, bulge+disk systems are the dominant late-stage merger galaxy type and are the dominant type for LIRGs and ULIRGs at almost every stage of galaxy-galaxy nuclear separation. The mean I-band host absolute magnitude of the GOALS galaxies is -22.64+/-0.62 mag (1.8_-0.4_^+1.4^ L_1_^*^), and the mean bulge absolute magnitude in GOALS galaxies is about 1.1 mag fainter than the mean host magnitude. Almost all ULIRGs have bulge magnitudes at the high end (-20.6 to -23.5 mag) of the GOALS bulge magnitude range. Mass ratios in the GOALS binary systems are consistent with most of the galaxies being the result of major mergers, and an examination of the residual-to-host intensity ratios in GOALS binary systems suggests that smaller companions suffer more tidal distortion than the larger companions. We find approximately twice as many bars in GOALS disk+bulge systems (32.8%) than in pure-disk mergers (15.9%) but most of the disk+bulge systems that contain bars are disk-dominated with small bulges. The bar-to-host intensity ratio, bar half-light radius, and bar ellipticity in GOALS galaxies are similar to those found in nearby spiral galaxies. The fraction of stellar bars decreases toward later merger stages and smaller nuclear separations, indicating that bars are destroyed as the merger advances. In contrast, the fraction of nuclear PSFs increases toward later merger stages and is highest in late-stage systems with a single nucleus. Thus, light from an active galactic nucleus or compact nuclear star cluster is more visible at I band as ULIRGs enter their latter stages of evolution. Finally, both GOALS elliptical hosts and nearby Sloan Digital Sky Survey (SDSS) ellipticals occupy the same part of the surface brightness versus half-light radius plot (i.e., the "Kormendy Relation") and have similar slopes, consistent with the possibility that the GOALS galaxies belong to the same parent population as the SDSS ellipticals.
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- ID:
- ivo://CDS.VizieR/J/AJ/157/169
- Title:
- Identifying exoplanets with deep learning in K2
- Short Name:
- J/AJ/157/169
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- For years, scientists have used data from NASA's Kepler Space Telescope to look for and discover thousands of transiting exoplanets. In its extended K2 mission, Kepler observed stars in various regions of the sky all across the ecliptic plane, and therefore in different galactic environments. Astronomers want to learn how the populations of exoplanets are different in these different environments. However, this requires an automatic and unbiased way to identify exoplanets in these regions and rule out false-positive signals that mimic transiting planet signals. We present a method for classifying these exoplanet signals using deep learning, a class of machine learning algorithms that have become popular in fields ranging from medical science to linguistics. We modified a neural network previously used to identify exoplanets in the Kepler field to be able to identify exoplanets in different K2 campaigns that exist in a range of galactic environments. We train a convolutional neural network, called AstroNet-K2, to predict whether a given possible exoplanet signal is really caused by an exoplanet or a false positive. AstroNet-K2 is highly successful at classifying exoplanets and false positives, with accuracy of 98% on our test set. It is especially efficient at identifying and culling false positives, but for now, it still needs human supervision to create a complete and reliable planet candidate sample. We use AstroNet-K2 to identify and validate two previously unknown exoplanets. Our method is a step toward automatically identifying new exoplanets in K2 data and learning how exoplanet populations depend on their galactic birthplace.
- ID:
- ivo://CDS.VizieR/J/A+A/628/A132
- Title:
- IK Tau and HIP 20188 visible polarimetric imaging
- Short Name:
- J/A+A/628/A132
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present visible polarimetric imaging observations of the oxygen-rich AGB star IK Tau obtained with SPHERE-ZIMPOL (phase 0.27) as well as interferometric observations with AMBER. The polarimetric imaging capabilities of SPHERE-ZIMPOL have allowed us to spatially resolve clumpy dust clouds at 20-50mas from the central star, which corresponds to 2-5R* when combined with a central star's angular diameter of 20.7+/-1.53 mas measured with AMBER. The diffuse, asymmetric dust emission extends out to ~73R*. We find that the TiO emission extends to 150 mas (15R*). The AMBER data in the CO lines also suggest a molecular outer atmosphere extending to ~1.5R*. The results of our 2-D Monte Carlo radiative transfer modelling of dust clumps suggest that the polarized intensity and degree of linear polarization can be reasonably explained by small-sized (0.1{mu}m) grains of Al_2_O_3, MgSiO_3, or Mg_2_SiO_4 in an optically thin shell ({tau}_550 nm=0.5+/-0.1) with an inner boundary radius of 3.5*. IK Tau's mass-loss rate is 20 to 50 times higher than the previously studied AGB stars W Hya, R Dor, and o Cet. Nevertheless, our observations of IK Tau revealed that clumpy dust formation occurs close to the star as seen in those low mass-rate AGB stars.
- ID:
- ivo://CDS.VizieR/J/A+AS/135/555
- Title:
- Illuminated atmospheres limb-darkening coeff. 1.
- Short Name:
- J/A+AS/135/555
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In Table 1 we present the bolometric and monochromatic limb-darkening coefficients for 196 different combinations of the parameters: T_eff (illuminated model's effective temperature), F_rel (relative incident flux, defined in Sect. 2.1), nu (the cosine of the incidence angle relative to the atmosphere normal), T_h (the effective temperature of the illuminating flux). We present coefficients for the linear, quadratic, cubic, logarithmic, and square root laws, together with the quality factor Q (see Sect. 2.2) of the fitting. In Table 2 we present the passband-specific limb-darkening coefficients. We present the coefficients for the Stroemgren uvby filters and for the Johnson-Morgan UBVRI filters. B2 and B3 are the response function of the B filter with and without the earth's atmosphere transmission function, respectively (see Buser R. 1998A&A....62..411B) In Table 3 we give the polynomial coefficients (Eqs. 8-11) for the Stroemgren uvby filters and for the Johnson-Morgan UBVRI filters and the five limb-darkening laws analysed.
- ID:
- ivo://CDS.VizieR/J/MNRAS/404/1295
- Title:
- Impact of gas pressure on transverse structure
- Short Name:
- J/MNRAS/404/1295
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We examine the impact of gas pressure on the transverse coherence of high-redshift (2>=z>=4) Lyman{alpha} (Lyalpha) forest absorption along neighbouring lines of sight that probe the gas Jeans scale (projected separation {Delta}rp<=500h^-1^kpc comoving, angular separation {Delta}{theta}<=30arcsec). We compare predictions from two smoothed particle hydrodynamics simulations that have different photoionization heating rates and thus different temperature-density relations in the intergalactic medium (IGM). We also compare spectra computed from the gas distributions to those computed from the pressureless dark matter.
- ID:
- ivo://CDS.VizieR/J/ApJ/869/167
- Title:
- Improved empirical models for Type Ia SNe
- Short Name:
- J/ApJ/869/167
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- SN Ia cosmology depends on the ability to fit and standardize observations of supernova magnitudes with an empirical model. We present here a series of new models of SN Ia spectral time series that capture a greater amount of supernova diversity than is possible with the models that are currently customary. These are entitled SuperNova Empirical MOdels (SNEMO; https://snfactory.lbl.gov/snemo). The models are constructed using spectrophotometric time series from 172 individual supernovae from the Nearby Supernova Factory, comprising more than 2000 spectra. Using the available observations, Gaussian processes are used to predict a full spectral time series for each supernova. A matrix is constructed from the spectral time series of all the supernovae, and Expectation Maximization Factor Analysis is used to calculate the principal components of the data. K-fold cross-validation then determines the selection of model parameters and accounts for color variation in the data. Based on this process, the final models are trained on supernovae that have been dereddened using the Fitzpatrick and Massa extinction relation. Three final models are presented here: SNEMO2, a two-component model for comparison with current Type Ia models; SNEMO7, a seven-component model chosen for standardizing supernova magnitudes, which results in a total dispersion of 0.100mag for a validation set of supernovae, of which 0.087mag is unexplained (a total dispersion of 0.113mag with an unexplained dispersion of 0.097mag is found for the total set of training and validation supernovae); and SNEMO15, a comprehensive 15-component model that maximizes the amount of spectral time-series behavior captured.
- ID:
- ivo://CDS.VizieR/J/AJ/119/1448
- Title:
- Improved properties for cool stars
- Short Name:
- J/AJ/119/1448
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new grids of colors and bolometric corrections for F-K stars having 4000 K {<=} Teff {<=} 6500 K, 0.0 {<=} log(g) {<=} 4.5, and -3.0 {<=} [Fe/H] {<=} 0.0. Colors are tabulated for Johnson U-V and B-V, Cousins V-R and V-I, Johnson-Glass V-K, J-K, and H-K, and CIT/CTIO V-K, J-K, H-K, and CO. We have developed these color-temperature relations by convolving synthetic spectra with the best-determined, photometric filter transmission profiles. The synthetic spectra have been computed with the SSG spectral synthesis code (Bell & Gustafsson 1978; Gustafsson & Bell 1979) using MARCS stellar atmosphere models (Gustafsson et al. 1975; Bell et al. 1976) as input. Both of these codes have been improved substantially, especially at low temperatures, through the incorporation of new opacity data. The resulting synthetic colors have been put onto the observational systems by applying color calibrations derived from models and photometry of field stars that have effective temperatures determined by the infrared flux method. These color calibrations have zero points that change most of the original synthetic colors by less than 0.02 mag, and the corresponding slopes generally alter the colors by less than 5%.
- ID:
- ivo://CDS.VizieR/J/ApJ/849/1
- Title:
- Insights from synthetic star-forming regions. II.
- Short Name:
- J/ApJ/849/1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use a large data set of realistic synthetic observations (produced in Paper I (2017ApJS..233....1K) of this series) to assess how observational techniques affect the measurement physical properties of star-forming regions. In this part of the series (Paper II), we explore the reliability of the measured total gas mass, dust surface density and dust temperature maps derived from modified blackbody fitting of synthetic Herschel observations. We find from our pixel-by-pixel analysis of the measured dust surface density and dust temperature a worrisome error spread especially close to star formation sites and low-density regions, where for those "contaminated" pixels the surface densities can be under/overestimated by up to three orders of magnitude. In light of this, we recommend to treat the pixel-based results from this technique with caution in regions with active star formation. In regions of high background typical in the inner Galactic plane, we are not able to recover reliable surface density maps of individual synthetic regions, since low-mass regions are lost in the far-infrared background. When measuring the total gas mass of regions in moderate background, we find that modified blackbody fitting works well (absolute error: +9%; -13%) up to 10kpc distance (errors increase with distance). Commonly, the initial images are convolved to the largest common beam-size, which smears contaminated pixels over large areas. The resulting information loss makes this commonly used technique less verifiable as now {chi}^2^ values cannot be used as a quality indicator of a fitted pixel. Our control measurements of the total gas mass (without the step of convolution to the largest common beam size) produce similar results (absolute error: +20%; -7%) while having much lower median errors especially for the high-mass stellar feedback phase.
- ID:
- ivo://CDS.VizieR/J/ApJ/849/2
- Title:
- Insights from synthetic star-forming regions. III.
- Short Name:
- J/ApJ/849/2
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Through an extensive set of realistic synthetic observations (produced in Paper I, 2017ApJS..233....1K), we assess in this part of the paper series (Paper III) how the choice of observational techniques affects the measurement of star formation rates (SFRs) in star-forming regions. We test the accuracy of commonly used techniques and construct new methods to extract the SFR, so that these findings can be applied to measure the SFR in real regions throughout the Milky Way. We investigate diffuse infrared SFR tracers such as those using 24{mu}m, 70{mu}m and total infrared emission, which have been previously calibrated for global galaxy scales. We set up a toy model of a galaxy and show that the infrared emission is consistent with the intrinsic SFR using extra-galactic calibrated laws (although the consistency does not prove their reliability). For local scales, we show that these techniques produce completely unreliable results for single star-forming regions, which are governed by different characteristic timescales. We show how calibration of these techniques can be improved for single star-forming regions by adjusting the characteristic timescale and the scaling factor and give suggestions of new calibrations of the diffuse star formation tracers. We show that star- forming regions that are dominated by high-mass stellar feedback experience a rapid drop in infrared emission once high-mass stellar feedback is turned on, which implies different characteristic timescales. Moreover, we explore the measured SFRs calculated directly from the observed young stellar population. We find that the measured point sources follow the evolutionary pace of star formation more directly than diffuse star formation tracers.
- ID:
- ivo://CDS.VizieR/J/MNRAS/403/1491
- Title:
- Integrated magnitudes of synthetic star clusters
- Short Name:
- J/MNRAS/403/1491
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper presents integrated magnitudes and colours for synthetic clusters. The integrated parameters have been obtained for the whole cluster population as well as for the main-sequence (MS) population of star clusters. We have also estimated observed integrated magnitudes and colours of the MS population of galactic open clusters, Large Magellanic Cloud (LMC) and Small Magellanic Cloud (SMC) star clusters.
