- ID:
- ivo://CDS.VizieR/J/ApJ/736/86
- Title:
- FeII emission in SDSS type 1 AGNs
- Short Name:
- J/ApJ/736/86
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We used a large, homogeneous sample of 4178 z<=0.8 Seyfert 1 galaxies and QSOs selected from the Sloan Digital Sky Survey to investigate the strength of FeII emission and its correlation with other emission lines and physical parameters of active galactic nuclei. We find that the strongest correlations of almost all the emission-line intensity ratios and equivalent widths (EWs) are with the Eddington ratio (L/L_Edd_), rather than with the continuum luminosity at 5100{AA} (L_5100_) or black hole mass (M_BH_); the only exception is the EW of ultraviolet FeII emission, which does not correlate at all with broad-line width, L_5100_, M_BH_, or L/L_Edd_. By contrast, the intensity ratios of both the ultraviolet and optical FeII emission to MgII{lambda}2800 correlate quite strongly with L/L_Edd_. Interestingly, among all the emission lines in the near-UV and optical studied in this paper (including MgII{lambda}2800, H{beta}, and [OIII]{lambda}5007), the EW of narrow optical FeII emission has the strongest correlation with L/L_Edd_. We hypothesize that the variation of the emission-line strength in active galaxies is regulated by L/L_Edd_ because it governs the global distribution of the hydrogen column density of the clouds gravitationally bound in the line-emitting region, as well as its overall gas supply. The systematic dependence on L/L_Edd_ must be corrected when using the FeII/MgII intensity ratio as a measure of the Fe/Mg abundance ratio to study the history of chemical evolution in QSO environments.
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/426/2522
- Title:
- FeK lines in Seyfert 1 galaxies
- Short Name:
- J/MNRAS/426/2522
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We construct full broad-band models in an analysis of Suzaku observations of nearby Seyfert 1 active galactic nuclei (AGN) (z<=0.2) with exposures >50ks and with greater than 30000 counts in order to study their iron line profiles. This results in a sample of 46 objects and 84 observations. After a full modelling of the broad-band Suzaku and Swift-Burst Alert Telescope data (0.6-100keV), we find complex warm absorption is present in 59 per cent of the objects in this sample which has a significant bearing upon the derived FeK region parameters. Meanwhile 35 per cent of the 46 objects require some degree of high column density partial coverer in order to fully model the hard X-ray spectrum. We also find that a large number of the objects in the sample (22 per cent) require high velocity, high ionization outflows in the FeK region resulting from FeXXV and FeXXVI. A further four AGN feature highly ionized FeK absorbers consistent with zero outflow velocity, making a total of 14/46 (30%) AGN in this sample showing evidence for statistically significant absorption in the FeK region.
- ID:
- ivo://CDS.VizieR/J/A+A/557/A100
- Title:
- Fermi and Swift GRBs E_peak_-E_iso_ relation
- Short Name:
- J/A+A/557/A100
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We used a sample of gamma-ray bursts (GRBs) detected by Fermi and Swift to reanalyze the correlation discovered by Amati et al. (2002A&A...390...81A) between E_pi_, the peak energy of the prompt GRB emission, and E_iso_, the energy released by the GRB assuming isotropic emission. This correlation has been disputed by various authors, and our aim is to assess whether it is an intrinsic GRB property or the consequence of selection effects. We constructed a sample of Fermi GRBs with homogeneous selection criteria, and we studied their distribution in the E_pi_-E_iso_ plane. Our sample is made of 43 GRBs with a redshift and 243 GRBs without a redshift. We show that GRBs with a redshift follow a broad E_pi_-E_iso_ relation, while GRBs without a redshift show several outliers. We use these samples to discuss the impact of selection effects associated with GRB detection and with redshift measurement.
- ID:
- ivo://CDS.VizieR/J/A+A/658/A57
- Title:
- F-G-K stars activity indicators
- Short Name:
- J/A+A/658/A57
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- Different relationships between the H{alpha} and CaII chromospheric emissions have been reported in solar-type stars. In particular, the time-series of emissions in these two lines are clearly anti-correlated for a few percent of the stars, contrary to what is observed on the Sun. Our objective is to characterise these relationships in more detail using complementary criteria, and to constrain the properties of filaments and plages that are necessary to explain the observations. We analysed the average level and variability of the H{alpha} and CaII emission for 441 F-G-K stars, paying particular attention to their (anti-)correlations on both short and long timescales. We also computed synthetic H{alpha} and CaII time-series for different assumptions of plage and filament properties and compared them with the observations. We were not able to find plage properties that, alone, are sufficient to reproduce the observations at all timescales simultaneously, even when allowing different H{alpha} and CaII emission relationships for different stars. We also specified the complex and surprising relationship between the average activity levels of both indexes, in particular for low-activity stars. We conclude that plages alone are unlikely to explain the observed variety of relationships between CaII and H{alpha} emission, and that the presence of other phenomena like filaments may help to reconcile the models with observations.
- ID:
- ivo://CDS.VizieR/J/ApJS/247/9
- Title:
- FGK stars magnetic activity in LAMOST-Kepler field
- Short Name:
- J/ApJS/247/9
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Monitoring chromospheric and photospheric indexes of magnetic activity can provide valuable information, especially the interaction between different parts of the atmosphere and their response to magnetic fields. We extract chromospheric indexes, S and R_HK_^+^, for 59816 stars from LAMOST spectra in the LAMOST-Kepler program, and photospheric index, Reff, for 5575 stars from Kepler light curves. The log Reff shows positive correlation with logR_HK_^+^. We estimate the power-law indexes between Reff and R_HK_^+^ for F-, G-, and K-type stars, respectively. We also confirm the dependence of both chromospheric and photospheric activity on stellar rotation. Ca ii H and K emissions and photospheric variations generally decrease with increasing rotation periods for stars with rotation periods exceeding a few days. The power-law indexes in exponential decay regimes show different characteristics in the two activity-rotation relations. The updated largest sample including the activity proxies and reported rotation periods provides more information to understand the magnetic activity for cool stars.
- ID:
- ivo://CDS.VizieR/VI/110
- Title:
- Final Merged Log of IUE Observations
- Short Name:
- VI/110
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The log contains a summary of all IUE Newly Extracted Spectra (INES), which resulted from a post-processing effort at Vilspa. It was constructed by using verified data from the IUE Final Archive Master Catalogue. The observations cover the whole life of the satellite, from March 1978 to September 1996.
- ID:
- ivo://CDS.VizieR/J/ApJS/226/19
- Title:
- FIR spectra of AGNs from Herschel
- Short Name:
- J/ApJS/226/19
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a coherent database of spectroscopic observations of far-IR fine-structure lines from the Herschel/Photoconductor Array Camera and Spectrometer (PACS) archive for a sample of 170 local active galactic nuclei (AGNs), plus a comparison sample of 20 starburst galaxies and 43 dwarf galaxies. Published Spitzer/IRS and Herschel/SPIRE line fluxes are included to extend our database to the full 10-600{mu}m spectral range. The observations are compared to a set of Cloudy photoionization models to estimate the above physical quantities through different diagnostic diagrams. We confirm the presence of a stratification of gas density in the emission regions of the galaxies, which increases with the ionization potential of the emission lines. The new [OIV]_25.9um_/[OIII]_88um_ versus [NeIII]_15.6um_/[NeII]_12.8um_ diagram is proposed as the best diagnostic to separate (1) AGN activity from any kind of star formation and (2) low-metallicity dwarf galaxies from starburst galaxies. Current stellar atmosphere models fail to reproduce the observed [OIV]_25.9um_/[OIII]_88um_ ratios, which are much higher when compared to the predicted values. Finally, the ([NeIII]_15.6um_+[NeII]_12.8um_)/([SIV]_10.5um_+[SIII]_18.7um_) ratio is proposed as a promising metallicity tracer to be used in obscured objects, where optical lines fail to accurately measure the metallicity. The diagnostic power of mid- to far-infrared spectroscopy shown here for local galaxies will be of crucial importance to study galaxy evolution during the dust-obscured phase at the peak of the star formation and black hole accretion activity (1<z<4). This study will be addressed by future deep spectroscopic surveys with present and forthcoming facilities such as the James Webb Space Telescope, the Atacama Large Millimeter/submillimeter Array, and the Space Infrared telescope for Cosmology and Astrophysics.
- ID:
- ivo://CDS.VizieR/J/ApJ/757/51
- Title:
- FIRST-2MASS dust-reddened QSO spectra
- Short Name:
- J/ApJ/757/51
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a sample of 120 dust-reddened quasars identified by matching radio sources detected at 1.4GHz in the Faint Images of the Radio Sky at Twenty Centimeters survey (FIRST) with the near-infrared Two Micron All Sky Survey catalog (2MASS) and color-selecting red sources. Optical and/or near-infrared spectroscopy provide broad wavelength sampling of their spectral energy distributions that we use to determine their reddening, characterized by E(B-V). We demonstrate that the reddening in these quasars is best described by Small-Magellanic-Cloud-like dust. This sample spans a wide range in redshift and reddening (0.1<~z<~3, 0.1<~E(B-V)<~1.5), which we use to investigate the possible correlation of luminosity with reddening. At every redshift, dust-reddened quasars are intrinsically the most luminous quasars. We interpret this result in the context of merger-driven quasar/galaxy co-evolution where these reddened quasars are revealing an emergent phase during which the heavily obscured quasar is shedding its cocoon of dust prior to becoming a "normal" blue quasar. When correcting for extinction, we find that, depending on how the parent population is defined, these red quasars make up <~15%-20% of the luminous quasar population. We estimate, based on the fraction of objects in this phase, that its duration is 15%-20% as long as the unobscured, blue quasar phase.
- ID:
- ivo://CDS.VizieR/J/ApJ/883/175
- Title:
- First release of the MaNGA Stellar Library (MaStar)
- Short Name:
- J/ApJ/883/175
- Date:
- 29 Nov 2021 07:46:33
- Publisher:
- CDS
- Description:
- We present the first release of the MaNGA Stellar Library (MaStar), which is a large, well-calibrated, high-quality empirical library covering the wavelength range 3622-10354{AA} at a resolving power of R~1800. The spectra were obtained using the same instrument as used by the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) project, by piggybacking on the Sloan Digital Sky Survey (SDSS-IV)/Apache Point Observatory Galaxy Evolution Experiment 2-N (APOGEE-2N) observations. Compared to previous empirical libraries, the MaStar library will have a higher number of stars and a more comprehensive stellar-parameter coverage, especially of cool dwarfs, low-metallicity stars, and stars with different [{alpha}/Fe], achieved by a sophisticated target-selection strategy that takes advantage of stellar-parameter catalogs from the literature. This empirical library will provide a new basis for stellar-population synthesis and is particularly well suited for stellar-population analysis of MaNGA galaxies. The first version of the library contains 8646 high-quality per-visit spectra for 3321 unique stars. Compared to photometry, the relative flux calibration of the library is accurate to 3.9% in g-r, 2.7% in r-i, and 2.2% in i-z. The data are released as part of SDSS Data Release 15. We expect the final release of the library to contain more than 10000 stars.
- ID:
- ivo://CDS.VizieR/J/AJ/151/142
- Title:
- Five years of blazar observations with VERITAS
- Short Name:
- J/AJ/151/142
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Between the beginning of its full-scale scientific operations in 2007 and 2012, the VERITAS Cherenkov telescope array observed more than 130 blazars; of these, 26 were detected as very-high-energy (VHE; E>100 GeV) {gamma}-ray sources. In this work, we present the analysis results of a sample of 114 undetected objects. The observations constitute a total live-time of ~570 hr. The sample includes several unidentified Fermi-Large Area Telescope (LAT) sources (located at high Galactic latitude) as well as all the sources from the second Fermi-LAT catalog (Nolan et al. 2012, J/ApJS/199/31) that are contained within the field of view of the VERITAS observations. We have also performed optical spectroscopy measurements in order to estimate the redshift of some of these blazars that do not have spectroscopic distance estimates. We present new optical spectra from the Kast instrument on the Shane telescope at the Lick observatory for 18 blazars included in this work, which allowed for the successful measurement or constraint on the redshift of four of them. For each of the blazars included in our sample, we provide the flux upper limit in the VERITAS energy band. We also study the properties of the significance distributions and we present the result of a stacked analysis of the data set, which shows a 4{sigma} excess.
