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1051. MgII line vs 3000{AA} continuum analysis in 68 QSOs
ID:
ivo://CDS.VizieR/J/ApJ/843/30
Title:
MgII line vs 3000{AA} continuum analysis in 68 QSOs
Short Name:
J/ApJ/843/30
Date:
21 Oct 2021
Publisher:
CDS
Description:
We investigate the relationship between the MgII{lambda}2798 emission line and the 3000{AA} continuum variations using a sample of 68 intermediate-redshift (z~0.65-1.50) broad-line quasars spanning a bolometric luminosity range of 44.49erg/s<=logL_bol_<=46.31erg/s (Eddington ratio from ~0.026 to 0.862). This sample is constructed from SDSS-DR7Q and BOSS-DR12Q, each with at least two spectroscopic epochs in SDSS-I/II/III surveys. In addition, we adopt the following signal-to-noise ratio (S/N) selection criteria: (a) for MgII and the 3000{AA} continuum, S/N>=10; and (b) for narrow lines, S/N>=5. All our quasar spectra are recalibrated based on the assumption of constant narrow emission- line fluxes. In an analysis of spectrum-to-spectrum variations, we find a fairly close correlation (Spearman {rho}=0.593) between the variations in broad MgII and in the continuum. This is consistent with the idea that MgII is varying in response to the continuum emission variations. Adopting the modified weighted least squares regression method, we statistically constrain the slopes (i.e., the responsivity {alpha} of the broad MgII) between the variations in both components for the sources in different luminosity bins after eliminating intrinsic biases introduced by the rescaling process itself. It is shown that the responsivity is quite small (average {bar}{alpha}~0.464) and anti- correlates with the quasar luminosity. Our results indicate that high signal- to-noise flux measurements are required to robustly detect the intrinsic variability and the time lag of the MgII line.
1052. MgII UV feature in T Tauri stars
ID:
ivo://CDS.VizieR/J/MNRAS/448/484
Title:
MgII UV feature in T Tauri stars
Short Name:
J/MNRAS/448/484
Date:
21 Oct 2021
Publisher:
CDS
Description:
The atmospheric structure of T Tauri stars (TTSs) and its connection with the large-scale outflow is poorly known. Neither the effect of the magnetically mediated interaction between the star and the disc is well understood. The MgII multiplet is a fundamental tracer of TTSs atmospheres and outflows, and is the strongest feature in the near-ultraviolet spectrum of TTSs. The International Ultraviolet Explorer and Hubble Space Telescope data archives provide a unique set to study the main physical compounds contributing to the line profile and to derive the properties of the line formation region. The MgII profiles of 44 TTSs with resolution 13000-30000 are available in these archives. In this work, we use this data set to measure the main observables: flux, broadening, asymmetry, terminal velocity of the outflow, and the velocity of the discrete absorption components. For some few sources repeated observations are available and variability has been studied. There is a warm wind that at sub-au scales absorbs the blue wing of the MgII profiles. The main result found in this work is the correlation between the line broadening, MgII flux, terminal velocity of the flow and accretion rate. Both outflow and magnetospheric plasma contribute to the MgII flux. The flux-flux correlation between MgII and CIV or HeII is confirmed; however, no correlation is found between the MgII flux and the UV continuum or the H_2_ emission.
1053. ~420MHz uGMRT obs. of MIR selected radio-loud AGN
ID:
ivo://CDS.VizieR/J/ApJS/255/28
Title:
~420MHz uGMRT obs. of MIR selected radio-loud AGN
Short Name:
J/ApJS/255/28
Date:
11 Mar 2022
Publisher:
CDS
Description:
We present results from a spectroscopically blind search for associated and intervening HI 21cm and OH 18cm absorption lines toward 88 active galactic nuclei (AGN) at 2<z<5 using the uGMRT. The sample of AGN with 1.4GHz spectral luminosity in the range 10^27-29.3^W/Hz is selected using mid-infrared colors and closely resembles the distribution of the underlying quasar population. The search for associated or proximate absorption, defined to be within 3000km/s of the AGN redshift, led to one HI 21cm absorption detection (M1540-1453; z_abs_=2.1139). This is only the fourth known absorption at z>2. The detection rate (1.6_-1.4_^+3.8^%) suggests a low covering factor of the cold neutral medium (CNM; T~100K) associated with these powerful AGN. The intervening absorption line search, with a sensitivity to detect the CNM in damped Ly{alpha} systems (DLAs), has comoving absorption path lengths of {Delta}X=130.1 and 167.7 for HI and OH, respectively. The corresponding number of absorbers per unit comoving path length are <=0.014 and <=0.011, respectively. The former is at least 4.5 times lower than that of DLAs and consistent with the CNM cross section estimated using H_2_ and CI absorbers at z>2. Our AGN sample is optically fainter compared to the quasars used to search for DLAs in the past. In our optical spectra obtained using SALT and NOT, we detect five intervening (redshift path ~9.3) and two proximate DLAs. This is slightly excessive compared to the statistics based on optically selected quasars. The nondetection of HI 21cm absorption from these DLAs suggests a small CNM covering fraction around galaxies at z>2.
1054. MIDI atlas of low- and intermediate-mass YSOs
ID:
ivo://CDS.VizieR/J/A+A/617/A83
Title:
MIDI atlas of low- and intermediate-mass YSOs
Short Name:
J/A+A/617/A83
Date:
21 Oct 2021
Publisher:
CDS
Description:
Protoplanetary disks show large diversity regarding their morphology and dust composition. With mid-infrared interferometry the thermal emission of disks can be spatially resolved, and the distribution and properties of the dust within can be studied. Our aim is to perform a statistical analysis on a large sample of 82 disks around low- and intermediate-mass young stars, based on mid-infrared interferometric observations. We intend to study the distribution of disk sizes, variability, and the silicate dust mineralogy. Archival mid-infrared interferometric data from the MIDI instrument on the Very Large Telescope Interferometer are homogeneously reduced and calibrated. Geometric disk models are used to fit the observations to get spatial information about the disks. An automatic spectral decomposition pipeline is applied to analyze the shape of the silicate feature. We present the resulting data products in the form of an atlas, containing N band correlated and total spectra, visibilities, and differential phases. The majority of our data can be well fitted with a continuous disk model, except for a few objects, where a gapped model gives a better match. From the mid-infrared size-luminosity relation we find that disks around T Tauri stars are generally colder and more extended with respect to the stellar luminosity than disks around Herbig Ae stars. We find that in the innermost part of the disks (r<~1au) the silicate feature is generally weaker than in the outer parts, suggesting that in the inner parts the dust is substantially more processed. We analyze stellar multiplicity and find that in two systems (AB Aur and HD 72106) data suggest a new companion or asymmetric inner disk structure. We make predictions for the observability of our objects with the upcoming Multi-AperTure mid- Infrared SpectroScopic Experiment (MATISSE) instrument, supporting the practical preparations of future MATISSE observations of T Tauri stars.
1055. Mid-infrared spectral variability atlas of YSOs
ID:
ivo://CDS.VizieR/J/ApJS/201/11
Title:
Mid-infrared spectral variability atlas of YSOs
Short Name:
J/ApJS/201/11
Date:
21 Oct 2021
Publisher:
CDS
Description:
The atlas presents medium-resolution mid-infrared spectra of low- and intermediate mass pre-main sequence objects obtained by the ISOPHOT-S spectrophotometer of the Infrared Space Observatory (ISO) and the Infrared Spectrograph (IRS) of the Spitzer Space Telescope.
1056. Mid-infrared spectroscopy of LINERs
ID:
ivo://CDS.VizieR/J/A+A/414/825
Title:
Mid-infrared spectroscopy of LINERs
Short Name:
J/A+A/414/825
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a comprehensive comparative high resolution mid-IR spectroscopic and X-ray imaging investigation of LINERs using archival observations from the ISO-SWS and the Chandra Advanced CCD Imaging Spectrometer. Although the sample is heterogeneous and incomplete, this is the first comprehensive study of the mid-infrared fine structure line emission of LINERs.
1057. Mid-IR emission lines in AGNs
ID:
ivo://CDS.VizieR/J/ApJ/725/2270
Title:
Mid-IR emission lines in AGNs
Short Name:
J/ApJ/725/2270
Date:
21 Oct 2021
Publisher:
CDS
Description:
We used Spitzer/Infrared Spectrograph spectroscopic data on 426 galaxies including quasars, Seyferts, LINERs, and HII galaxies to investigate the relationship among the mid-IR emission lines. There is a tight linear correlation between the [NeV]14.3um and 24.3um (97.1eV) and the [OIV]25.9um (54.9eV) high-ionization emission lines. The correlation also holds for these high-ionization emission lines and the [NeIII]15.56um (41eV) emission line, although only for active galaxies. We used these correlations to calculate the [NeIII] excess due to star formation in Seyfert galaxies. We also estimated the [OIV] luminosity due to star formation in active galaxies and determined that it dominates the [OIV] emission only if the contribution of the active nucleus to the total luminosity is below 5%. We find that the active galactic nucleus dominates the [OIV] emission in most Seyfert galaxies, whereas star formation adequately explains the observed [OIV] emission in optically classified HII galaxies. Finally, we computed photoionization models to determine the physical conditions of the narrow-line region where these high-ionization lines originate. The estimated ionization parameter range is -2.8<logU<-2.5 and the total hydrogen column density range is 20<logn_H_(cm^-2^)<21.
1058. Mid-IR indicators of SF and AGN in galaxies
ID:
ivo://CDS.VizieR/J/ApJ/719/1191
Title:
Mid-IR indicators of SF and AGN in galaxies
Short Name:
J/ApJ/719/1191
Date:
21 Oct 2021
Publisher:
CDS
Description:
We investigate the use of mid-infrared (MIR) polycyclic aromatic hydrocarbon (PAH) bands, the continuum, and emission lines as probes of star formation (SF) and active galactic nucleus (AGN) activity in a sample of 100 "normal" and local (z~0.1) emission-line galaxies. The MIR spectra were obtained with the Spitzer Space Telescope Infrared Spectrograph as part of the Spitzer-SDSS-GALEX Spectroscopic Survey (SSGSS), which includes multi-wavelength photometry from the ultraviolet to the far-infrared and optical spectroscopy. The continuum and features were extracted using PAHFIT, a decomposition code which we find to yield PAH equivalent widths (EWs) up to ~30 times larger than the commonly used spline methods. Despite the lack of extreme objects in our sample (such as strong AGNs, low-metallicity galaxies, or ULIRGs), we find significant variations in PAH, continuum, and emission-line properties, and systematic trends between these MIR properties and optically derived physical properties, such as age, metallicity, and radiation field hardness. We revisit the diagnostic diagram relating PAH EWs and [NeII]12.8um/[OIV]25.9um line ratios and find it to be in much better agreement with the standard optical SF/AGN classification than when spline decompositions are used, while also potentially revealing obscured AGNs.
1059. Mid-IR properties of GOALS nearby LIRGs
ID:
ivo://CDS.VizieR/J/ApJS/206/1
Title:
Mid-IR properties of GOALS nearby LIRGs
Short Name:
J/ApJS/206/1
Date:
21 Oct 2021
Publisher:
CDS
Description:
The Great Observatories All-Sky LIRG Survey (GOALS, Armus et al. 2009PASP..121..559A) is a comprehensive, multiwavelength study of luminous infrared galaxies (LIRGs) in the local universe. Here we present low resolution Spitzer Infrared Spectrograph spectra covering 5-38um and provide a basic analysis of the mid-IR spectral properties observed for nearby LIRGs. In a companion paper, we discuss detailed fits to the spectra and compare the LIRGs to other classes of galaxies. The GOALS sample of 244 nuclei in 180 luminous (10^11^<=L_IR_/L_{sun}_<10^12^) and 22 ultraluminous (L_IR_/L_{sun}_>=10^12^) IR galaxies represents a complete subset of the IRAS Revised Bright Galaxy Sample (Sanders, 2003, Cat. J/AJ/126/1607) and covers a range of merger stages, morphologies, and spectral types. The majority (>60%) of the GOALS LIRGs have high 6.2um polycyclic aromatic hydrocarbon (PAH) equivalent widths (EQW_6.2um_>0.4um) and low levels of silicate absorption (s_9.7um_>-1.0).
1060. Mid-IR QSO spectral templates
ID:
ivo://CDS.VizieR/J/MNRAS/438/2317
Title:
Mid-IR QSO spectral templates
Short Name:
J/MNRAS/438/2317
Date:
21 Oct 2021
Publisher:
CDS
Description:
Mid-infrared (MIR) quasar spectra exhibit a suite of emission features including high ionization coronal lines from the narrow-line region illuminated by the ionizing continuum, broad dust bumps from silicates and graphites, and polycyclic aromatic hydrocarbon (PAH) features from star formation in the host galaxy. However, in Spitzer Infared Spectrograph (IRS) data, few features are detected in most individual spectra because of typically low signal-to-noise ratios (S/N). By generating spectral composites from over 180 IRS observations of Sloan Digital Sky Survey broad-line quasars, we boost the S/N and reveal features in the complex spectra that are otherwise lost in the noise. In addition to an overall composite, we generate composites in three different luminosity bins that span the range of 5.6{mu}m luminosities of 10^40^-10^46^ (erg/s). We detect the high-ionization, forbidden emission lines of [SIV], [OIV] and [NeV] {lambda}14um in all templates and PAH features in all but the most luminous template.