- ID:
- ivo://CDS.VizieR/J/ApJ/895/38
- Title:
- MIR extinction toward Cyg OB2-12 ISM
- Short Name:
- J/ApJ/895/38
- Date:
- 11 Mar 2022
- Publisher:
- CDS
- Description:
- The sight line toward the luminous blue hypergiant CygOB2-12 is widely used to study interstellar dust on account of its large extinction (AV~10mag) and the fact that this extinction appears to be dominated by dust typical of the diffuse interstellar medium. We present a new analysis of archival Infrared Space Observatory Short Wavelength Spectrometer and Spitzer IRS observations of CygOB2-12 using a model of the emission from the star and its stellar wind to determine the total extinction A{lambda} from 2.4 to 37{mu}m. In addition to the prominent 9.7 and 18{mu}m silicate features, we robustly detect absorption features associated with polycyclic aromatic hydrocarbons, including the first identification of the 7.7{mu}m feature in absorption. The 3.3{mu}m aromatic feature is found to be much broader in absorption than is typically seen in emission. The 3.4 and 6.85{mu}m aliphatic hydrocarbon features are observed with relative strengths that are consistent with observations of these features on sight lines toward the Galactic center. We identify and characterize more than 60 spectral lines in this wavelength range, which may be useful in constraining models of the star and its stellar wind. Based on this analysis, we present an extinction curve A_{lambda}_/A_2.2{mu}m_ that extrapolates smoothly to determinations of the mean Galactic extinction curve at shorter wavelengths and to dust opacities inferred from emission at longer wavelengths, providing a new constraint on models of interstellar dust in the mid-infrared.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/791/113
- Title:
- MIR-selected quasar parameters
- Short Name:
- J/ApJ/791/113
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We provide a catalog of 391 mid-infrared-selected (MIR; 24 {mu}m) broad-emission-line (BEL; type 1) quasars in the 22 deg^2^ SWIRE Lockman Hole field. This quasar sample is selected in the MIR from Spitzer MIPS with S_24_> 400 {mu}Jy, jointly with an optical magnitude limit of r(AB) < 22.5 for broad line identification. The catalog is based on MMT and Sloan Digital Sky Survey (SDSS) spectroscopy to select BEL quasars, extending the SDSS coverage to fainter magnitudes and lower redshifts, and recovers a more complete quasar population. The MIR-selected quasar sample peaks at z ~ 1.4 and recovers a significant and constant (20%) fraction of extended objects with SDSS photometry across magnitudes, which were not included in the SDSS quasar survey dominated by point sources. This sample also recovers a significant population of z < 3 quasars at i > 19.1. We then investigate the continuum luminosity and line profiles of these MIR quasars, and estimate their virial black hole masses and the Eddington ratios. The supermassive black hole mass shows evidence of downsizing, although the Eddington ratios remain constant at 1 < z < 4. Compared to point sources in the same redshift range, extended sources at z < 1 show systematically lower Eddington ratios. The catalog and spectra are publicly available online.
- ID:
- ivo://CDS.VizieR/J/ApJ/701/1123
- Title:
- MIR spectroscopic catalog of 150 galaxies
- Short Name:
- J/ApJ/701/1123
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalog of mid-infrared (MIR) spectra of 150 infrared (IR) luminous galaxies in the Spitzer extragalactic first look survey obtained with the IR spectrograph on board the Spitzer Space Telescope. The sample is selected to be brighter than ~0.9mJy at 24um and it has a redshift distribution in the range [0.3, 3.5], with a peak at z=1. It primarily comprises ultraluminous IR galaxies (ULIRGs) at z>~1 and luminous IR galaxies at z<1, as estimated from their monochromatic rest-frame 14um luminosities. The number of sources with spectra that are dominated by an active galactic nucleus (AGN) continuum is 49, while 39 sources have strong, star formation related features.
- ID:
- ivo://CDS.VizieR/J/ApJ/696/471
- Title:
- MIR spectroscopy of NGC 7538 IRS 1
- Short Name:
- J/ApJ/696/471
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present high-resolution (R=75000-100000) mid-infrared spectra of the high-mass embedded young star IRS 1 in the NGC 7538 star-forming region. Absorption lines from many rotational states of C_2_H_2_, ^13^C^12^CH_2_, CH_3_, CH_4_, NH_3_, HCN, HNCO, and CS are seen. The gas temperature, column density, covering factor, line width, and Doppler shift for each molecule are derived. All molecules were fit with two velocity components between -54 and -63km/s. We find high column densities (~10^16^cm^-2^) for all the observed molecules compared to values previously reported and present new results for CH_3_ and HNCO. Several physical and chemical models are considered. The favored model involves a nearly edge-on disk around a massive star. Radiation from dust in the inner disk passes through the disk atmosphere, where large molecular column densities can produce the observed absorption line spectrum.
- ID:
- ivo://CDS.VizieR/J/ApJ/822/109
- Title:
- MIR view of polar dust emission in local AGNs
- Short Name:
- J/ApJ/822/109
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Recent mid-infrared (MIR) interferometric observations have shown that in a few active galactic nuclei (AGNs) the bulk of the infrared emission originates from the polar region above the putative torus, where only a little dust should be present. Here, we investigate whether such strong polar dust emission is common in AGNs. Out of 149 Seyferts in the MIR atlas of local AGNs, 21 show extended MIR emission on single-dish images. In 18 objects, the extended MIR emission aligns with the position angle (PA) of the system axis, established by [O III], radio, polarization, and maser-based PA measurements. The relative amount of resolved MIR emission is at least 40% and scales with the [O IV] fluxes, implying a strong connection between the extended continuum and [O IV] emitters. These results together with the radio-quiet nature of the Seyferts support the scenario that the bulk of MIR emission is emitted by dust in the polar region and not by the torus, which would demand a new paradigm for the infrared emission structure in AGNs. The current low detection rate of polar dust in the AGNs of the MIR atlas is explained by the lack of sufficient high-quality MIR data and the requirements on the orientation, strength of narrow-line region, and distance of the AGNs. The James Webb Space Telescope will enable much deeper nuclear MIR studies with comparable angular resolution, allowing us to resolve the polar emission and surroundings in most of the nearby AGNs.
- ID:
- ivo://CDS.VizieR/J/A+A/474/911
- Title:
- 1.3mm and CO(2-1) maps of IRAS 20343+4129
- Short Name:
- J/A+A/474/911
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- IRAS 20343+4129 was suggested to harbor one of the most massive and embedded stars in the Cygnus OB2 association, IRS 1, which seemed to be associated with a north-south molecular outflow. However, the dust emission peaks do not coincide with the position of IRS 1, but lie on either side of another massive Young Stellar Object (YSO), IRS 3, which is associated with centimeter emission. The goal of this work is to elucidate the nature of IRS 1 and IRS 3, and study their interactions with the surrounding medium.
- ID:
- ivo://CDS.VizieR/J/A+A/426/119
- Title:
- 1.2mm mapping of RCW 106 Giant Molecular Cloud
- Short Name:
- J/A+A/426/119
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have mapped the dust continuum emission from the molecular cloud covering a region of 28pcx94pc associated with the well-known H II region RCW 106 at 1.2mm using SIMBA on SEST. The observations, having an HPBW of 24" (0.4pc), reveal 95 clumps, of which about 50% have MSX associations and only 20% have IRAS associations. Owing to their higher sensitivity to colder dust and higher angular resolution the present observations identify new emission features and also show that most of the IRAS sources in this region consist of multiple dust emission peaks. The detected millimeter sources (MMS) include on one end the exotic MMS5 (associated with IRAS 16183-4958, one of the brightest infrared sources in our Galaxy) and the bright (and presumably cold) source MMS54, with no IRAS or MSX associations on the other end. Around 10% of the sources are associated with signposts of high mass star formation activity.
- ID:
- ivo://CDS.VizieR/J/A+A/499/149
- Title:
- 1.2mm maps of southern Infrared Dark Clouds
- Short Name:
- J/A+A/499/149
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- What are the mechanisms by which massive stars form? What are the initial conditions for these processes? It is commonly assumed that cold and dense Infrared Dark Clouds (IRDCs) likely represent the birth sites massive stars. Therefore, this class of objects gets increasing attention, and their analysis offers the opportunity to tackle the above mentioned questions. To enlarge the sample of well-characterised IRDCs in the southern hemisphere, where ALMA will play a major role in the near future, we have set up a program to study the gas and dust of southern infrared dark clouds. The present paper aims at characterizing the continuum properties of this sample of IRDCs. We cross-correlated 1.2 mm continuum data from SIMBA@SEST with Spitzer/GLIMPSE images to establish the connection between emission sources at millimeter wavelengths a nd the IRDCs we see at 8{mu}m in absorption against the bright PAH background. Analysing the dust emission and extinction leads to a determination of masses and column densities, which are important quantities in characterizing the initial conditions of massive star formation. We also evaluated the limitations of the emission and extinction methods. The morphology of the 1.2mm continuum emission is in all cases in close agreement with the mid-infrared extinction. The total masses of the IRDCs were found to range from 150 to 1150M_{sun}_ (emission data) and from 300 to 1750M_{sun}_ (extinction data). We derived peak column densities between 0.9 and 4.6x10^22^cm^-2^ (emission data) and 2.1 and 5.4x10^22^cm^-2^ (extinction data). We demonstrate that the extinction method fails for very high extinction values (and column densities) beyond A_V_ values of roughly 75mag according to the Weingartner & Draine (2001ApJ...548..296W) extinction relation R_V_=5.5 model B (around 200mag when following the common Mathis (1990ARA&A..28...37M) extinction calibration). By taking the spatial resolution effects into account and restoring the column densities derived from the dust emission back to a linear resolution of 0.01pc, peak column densities of 3.0x10^23^cm^-2^ are obtained, much higher than typic al values for low-mass cores. The derived column densities, taking into account the spatial resolution effects, are beyond the column density threshold of 3.0x10^23^cm^-2^ required by theoretical considerations for massive star formation. We conclude that the values for column densities derived for the selected IRDC sample make these objects excellent candidates for objects in the earliest stages of massive star formation.
- ID:
- ivo://CDS.VizieR/J/ApJS/202/1
- Title:
- 1mm spectral line survey toward GLIMPSE EGOs
- Short Name:
- J/ApJS/202/1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A northern subsample of 89 Spitzer GLIMPSE extended green objects (EGOs), the candidate massive young stellar objects, are surveyed for molecular lines in two 1GHz ranges: 251.5-252.5 and 260.188-261.188GHz. A comprehensive catalog of observed molecular line data and spectral plots are presented. Eight molecular species are undoubtedly detected: H^13^CO^+^, SiO, SO, CH_3_OH, CH_3_OCH_3_, CH_3_CH_2_CN, HCOOCH_3_, and HN^13^C. The H^13^CO^+^ 3-2 line is detected in 70 EGOs, among which 37 also show the SiO 6-5 line, demonstrating their association with dense gas and supporting the outflow interpretation of the extended 4.5um excess emission. Our major dense gas and outflow tracers (H^13^CO^+^, SiO, SO, and CH_3_OH) are combined with our previous survey of ^13^CO, ^12^CO, and C^18^O 1-0 toward the same sample of EGOs for a multi-line, multi-cloud analysis of linewidth and luminosity correlations.
- ID:
- ivo://CDS.VizieR/J/ApJS/216/2
- Title:
- MnI hyperfine lines in the 1.4-1.8um (H) band
- Short Name:
- J/ApJS/216/2
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The three Mn I lines at 17325, 17339, and 17349{AA} are among the 25 strongest lines (log(gf)>0.5) in the H band. They are all heavily broadened due to hyperfine structure, and the profiles of these lines have so far not been understood. Earlier studies of these lines even suggested that they were blended. In this work, the profiles of these three infrared (IR) lines have been studied theoretically and compared to experimental spectra to assist in the complete understanding of the solar spectrum in the IR. It is shown that the structure of these lines cannot be described in the conventional way using the diagonal A and B hyperfine interaction constants. The off-diagonal hyperfine interaction not only has a large impact on the energies of the hyperfine levels, but also introduces a large intensity redistribution among the hyperfine lines, changing the line profiles dramatically. By performing large-scale calculations of the diagonal and off-diagonal hyperfine interaction and the gf-values between the upper and lower hyperfine levels and using a semi-empirical fitting procedure, we achieved agreement between our synthetic and experimental spectra. Furthermore, we compare our results with observations of stellar spectra. The spectra of the Sun and the K1.5 III red giant star Arcturus were modeled in the relevant region, 1.73-1.74{mu}m, using our theoretically predicted gf-values and energies for each individual hyperfine line. Satisfactory fits were obtained and clear improvements were found using our new data compared with the old available Mn I data.
