- ID:
- ivo://CDS.VizieR/J/ApJ/884/136
- Title:
- PAH features of star-forming gal. using Spitzer/IRS
- Short Name:
- J/ApJ/884/136
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Polycyclic aromatic hydrocarbon (PAH) emission has long been proposed to be a potential star formation rate indicator, as it arises from the photodissociation region bordering the Stromgren sphere of young, massive stars. We apply a recently developed technique of mid-infrared spectral decomposition to obtain a uniform set of PAH measurements from Spitzer low-resolution spectra of a large sample of star-forming galaxies spanning a wide range in stellar mass (M_*_~10^6^-10^11.4^M_{sun}_) and star formation rate (~0.1-2000M_{sun}_/yr). High-resolution spectra are also analyzed to measure [NeII]12.8{mu}m and [NeIII]15.6{mu}m, which effectively trace the Lyman continuum. We present a new relation between PAH luminosity and star formation rate based on the [NeII] and [NeIII] lines. Calibrations are given for the integrated 5-15{mu}m PAH emission, the individual features at 6.2, 7.7, 8.6, and 11.3{mu}m, as well as several mid- infrared bandpasses sensitive to PAH. We confirm that PAH emission is suppressed in low-mass dwarf galaxies, and we discuss the possible physical origin of this effect.
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902. PAH hypothesis
- ID:
- ivo://CDS.VizieR/J/A+A/319/318
- Title:
- PAH hypothesis
- Short Name:
- J/A+A/319/318
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- IR spectra of anthracene and pyrene derivatives, serving as models for isolated, linear and isolated, compact PAHs, respectively, have been calculated using ab-initio quantum mechanical methods. The separate and combined effects of ionization and multiple dehydrogenation have been studied. This study confirms and refines the trends of our preliminary paper on the smallest possible PAH, naphthalene. If small PAHs are responsible for any UIR bands, they should be ionized and partially dehydrogenated, with a few triple bonds at the periphery of the carbon skeleton. In the appendix are given the complete IR spectra of all the isomers of the derivatives of anthracene and pyrene calculated for the purpose of this study. Tables I are for anthracene and Tables II for pyrene. Positions of the the missing hydrogens in the dehydrogenated species are referred as in Figures 1 and 2 of the original publication.
- ID:
- ivo://CDS.VizieR/J/ApJ/705/885
- Title:
- PAH in galaxies at z~0.1
- Short Name:
- J/ApJ/705/885
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the analysis of the polycyclic aromatic hydrocarbon (PAH) spectra of a sample of 92 typical star-forming galaxies at 0.03<z<0.2 observed with the Spitzer intensified Reticon spectrograph (IRS). We compare the relative strengths of PAH emission features with Sloan Digital Sky Survey optical diagnostics to probe the relationship between PAH grain properties and star formation and active galactic nuclei (AGNs) activity. Short-to-long wavelength PAH ratios, and in particular the 7.7um-to-11.3um feature ratio, are strongly correlated with the star formation diagnostics D_n_(4000) and H{alpha} equivalent width, increasing with younger stellar populations. This ratio also shows a significant difference between active and non-active galaxies, with the active galaxies exhibiting weaker 7.7um emission. A hard radiation field as measured by [OIII]/H{beta} and [NeIII]_15.6um_/[NeII]_12.8um_ effects PAH ratios differently depending on whether this field results from starburst activity or an AGN. Our results are consistent with a picture in which larger PAH molecules grow more efficiently in richer media and in which smaller PAH molecules are preferentially destroyed by the AGN.
- ID:
- ivo://CDS.VizieR/J/ApJS/240/19
- Title:
- Parallaxes of late-T and Y dwarfs
- Short Name:
- J/ApJS/240/19
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present preliminary trigonometric parallaxes of 184 late-T and Y dwarfs using observations from Spitzer (143), the U.S. Naval Observatory (18), the New Technology Telescope (14), and the United Kingdom Infrared Telescope (9). To complete the 20pc census of >=T6 dwarfs, we combine these measurements with previously published trigonometric parallaxes for an additional 44 objects and spectrophotometric distance estimates for another 7. For these 235 objects, we estimate temperatures, sift into five 150K wide T_eff_ bins covering the range 300-1050K, determine the completeness limit for each, and compute space densities. To anchor the high-mass end of the brown dwarf mass spectrum, we compile a list of early- to mid-L dwarfs within 20pc. We run simulations using various functional forms of the mass function passed through two different sets of evolutionary code to compute predicted distributions in T_eff_. The best fit of these predictions to our L, T, and Y observations is a simple power-law model with {alpha}~0.6 (where dN/dM{propto}M^-{alpha}^), meaning that the slope of the field substellar mass function is in rough agreement with that found for brown dwarfs in nearby star-forming regions and young clusters. Furthermore, we find that published versions of the log-normal form do not predict the steady rise seen in the space densities from 1050 to 350K. We also find that the low-mass cutoff to formation, if one exists, is lower than ~5M_Jup_, which corroborates findings in young, nearby moving groups and implies that extremely low-mass objects have been forming over the lifetime of the Milky Way.
- ID:
- ivo://CDS.VizieR/J/MNRAS/471/770
- Title:
- Parameters and IR excesses of Gaia DR1 stars
- Short Name:
- J/MNRAS/471/770
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Effective temperatures and luminosities are calculated for 1,475,921 Tycho-2 and 107,145 Hipparcos stars, based on distances from Gaia Data Release 1. Parameters are derived by comparing multi-wavelength archival photometry to BT-Settl model atmospheres. The 1-sigma uncertainties for the Tycho-2 and Hipparcos stars are +/-137K and +/-125K in temperature and +/-35 per cent and +/-19 per cent in luminosity. The luminosity uncertainty is dominated by that of the Gaia parallax. Evidence for infrared excess between 4.6 and 25 microns is found for 4256 stars, of which 1883 are strong candidates. These include asymptotic giant branch (AGB) stars, Cepheids, Herbig Ae/Be stars, young stellar objects, and other sources. We briefly demonstrate the capabilities of this dataset by exploring local interstellar extinction, the onset of dust production in AGB stars, the age and metallicity gradients of the solar neighbourhood and structure within the Gould Belt. We close by discussing the potential impact of future Gaia data releases.
- ID:
- ivo://CDS.VizieR/J/AJ/159/254
- Title:
- Parameters for 453 metal-poor stars in NGC5139
- Short Name:
- J/AJ/159/254
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The most massive and complex globular clusters in the Galaxy are thought to have originated as the nuclear cores of now tidally disrupted dwarf galaxies, but the connection between globular clusters and dwarf galaxies is tenuous with the M54/Sagittarius system representing the only unambiguous link. The globular cluster Omega Centauri ({omega}Cen) is more massive and chemically diverse than M54, and is thought to have been the nuclear star cluster of either the Sequoia or Gaia-Enceladus galaxy. Local Group dwarf galaxies with masses equivalent to these systems often host significant populations of very metal-poor stars ([Fe/H]<-2.5), and one might expect to find such objects in {omega}Cen. Using high-resolution spectra from Magellan-M2FS, we detected 11 stars in a targeted sample of 395 that have [Fe/H] ranging from -2.30 to -2.52. These are the most metal-poor stars discovered in the cluster, and are five times more metal-poor than {omega}Cen's dominant population. However, these stars are not so metal-poor as to be unambiguously linked to a dwarf galaxy origin. The cluster's metal-poor tail appears to contain two populations near [Fe/H]~-2.1 and -2.4, which are very centrally concentrated but do not exhibit any peculiar kinematic signatures. Several possible origins for these stars are discussed.
- ID:
- ivo://CDS.VizieR/J/A+A/523/A58
- Title:
- PDF Atlas and spectra of FeH molecule in LHS 2
- Short Name:
- J/A+A/523/A58
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an atlas for the iron-hydride molecule (FeH) in the z-range (990nm to 1076.6nm). We used high-resolution CRIRES spectra of the M-dwarf GJ1002, which is an ideal target for the investigation of FeH, because it is only very slow rotating (<3km/s) and exhibits only weak magnetic fields. The identified lines stem mainly from the (0-0) and (1-1) vibronic transitions, but also from the (1-0), (2-1), (2-2), (3-2), and (4-3) transitions. For the confirmation of the identifications, we used means of statistic and cross-correlation as well as the line intensities. We corrected the theoretical positions if needed and scaled the line intensities till they match the observations.
- ID:
- ivo://CDS.VizieR/J/A+A/659/A13
- Title:
- PG 2130+099 narrowband light curves
- Short Name:
- J/A+A/659/A13
- Date:
- 25 Feb 2022 07:32:33
- Publisher:
- CDS
- Description:
- We present the results of an intensive six-month optical continuum reverberation mapping campaign of the Seyfert 1 galaxy PG 2130+099 at redshift z=0.063. The ground- based photometric monitoring was conducted on a daily basis with the robotic 46cm telescope of the Wise observatory located in Israel. Specially designed narrowband filters were used to observe the central engine of the active galactic nucleus (AGN), avoiding line contamination from the broad-line region (BLR). We aim to measure inter- band continuum time lags across the optical range and determine the size-wavelength relation for this system. PG 2130+099 displays correlated variability across the optical range, and we successfully detect significant time lags of up to 3 days between the multiband light curves. While a continuum reprocessing model can fit the data reasonably well, our derived disk sizes are a factor of 2-6 larger than the theoretical disk sizes predicted from the AGN luminosity estimate of PG 2130+099. This result is in agreement with previous studies of AGN/quasars and suggests that the standard Shakura- Sunyaev disk theory has limitations in describing AGN accretion disks.
- ID:
- ivo://CDS.VizieR/J/ApJS/215/9
- Title:
- PHAT X. UV-IR photometry of M31 stars
- Short Name:
- J/ApJS/215/9
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have measured stellar photometry with the Hubble Space Telescope Wide Field Camera 3 (WFC3) and Advanced Camera for Surveys in near ultraviolet (F275W, F336W), optical (F475W, F814W), and near infrared (F110W, F160W) bands for 117 million resolved stars in M31. As part of the Panchromatic Hubble Andromeda Treasury survey, we measured photometry with simultaneous point-spread function (PSF) fitting across all bands and at all source positions after precise astrometric image alignment (<5-10mas accuracy). In the outer disk, the photometry reaches a completeness-limited depth of F475W~28, while in the crowded, high surface brightness bulge, the photometry reaches F475W~25. We find that simultaneous photometry and optimized measurement parameters significantly increase the detection limit of the lowest-resolution filters (WFC3/IR) providing color-magnitude diagrams (CMDs) that are up to 2.5mag deeper when compared with CMDs from WFC3/IR photometry alone. We present extensive analysis of the data quality including comparisons of luminosity functions and repeat measurements, and we use artificial star tests to quantify photometric completeness, uncertainties and biases. We find that the largest sources of systematic error in the photometry are due to spatial variations in the PSF models and charge transfer efficiency corrections.
- ID:
- ivo://CDS.VizieR/II/18
- Title:
- Photometric Measurements, Eggen (102,65,62) System
- Short Name:
- II/18
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A catalog of photometric measures in Eggen's (102, 65, 62) system has been compiled at the Institut d'Astronomie de l'Universite de Lausanne. A catalog of individual observations and of weighted means are included, with an explanation of the coded numbering system.
