- ID:
- ivo://CDS.VizieR/J/ApJ/834/185
- Title:
- IR-bright MSX sources in the SMC with Spitzer/IRS
- Short Name:
- J/ApJ/834/185
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have used the Infrared Spectrograph (IRS) on the Spitzer Space Telescope to observe stars in the Small Magellanic Cloud (SMC) selected from the Point Source Catalog of the Midcourse Space Experiment (MSX). We concentrate on the dust properties of the oxygen-rich evolved stars. The dust composition has smaller contributions from alumina compared to the Galaxy. This difference may arise from the lower metallicity in the SMC, but it could be a selection effect, as the SMC sample includes more stars that are brighter and thus more massive. The distribution of the SMC stars along the silicate sequence looks more like the Galactic sample of red supergiants than asymptotic giant branch stars (AGBs). While many of the SMC stars are definitively on the AGB, several also show evidence of hot bottom burning. Three of the supergiants show PAH emission at 11.3{mu}m. Two other sources show mixed chemistry, with both carbon-rich and oxygen-rich spectral features. One, MSX SMC 134, may be the first confirmed silicate/carbon star in the SMC. The other, MSX SMC 049, is a candidate post-AGB star. MSX SMC 145, previously considered a candidate OH/IR star, is actually an AGB star with a background galaxy at z=0.16 along the same line of sight. We consider the overall characteristics of all the MSX sources, the most infrared-bright objects in the SMC, in light of the higher sensitivity and resolution of Spitzer, and compare them with the object types expected from the original selection criteria. This population represents what will be seen in more distant galaxies by the upcoming James Webb Space Telescope (JWST). Color-color diagrams generated from the IRS spectra and the mid-infrared filters on JWST show how one can separate evolved stars from young stellar objects (YSOs) and distinguish among different classes of YSOs.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/618/A4
- Title:
- IRC+10216 as a spectroscopic laboratory
- Short Name:
- J/A+A/618/A4
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This work presents a detailed analysis of the laboratory and astrophysical spectral data available for ^28^SiC_2_, ^29^SiC_2_, ^30^SiC_2_, Si^13^CC, and Si_2_C. New data on the rotational lines of these species between 70 and 350GHz have been obtained with high spectral resolution (195kHz) with the IRAM 30m telescope in the direction of the circumstellar envelope IRC+10216. Frequency measurements can reach an accuracy of 50kHz for features observed with a good signal to noise ratio. From the observed astrophysical lines and the available laboratory data new rotational and centrifugal distortion constants have been derived for all the isotopologues of SiC_2_, allowing to predict their spectrum with high accuracy in the millimeter and submillimeter domains. Improved rotational and centrifugal distortion constants have also been obtained for disilicon carbide, Si_2_C. This work shows that observations of IRC+10216 taken with the IRAM 30m telescope, with a spectral resolution of 195kHz, can be used for any molecular species detected in this source to derive, or improve, its rotational constants. Hence, IRC+10216 in addition to be one the richest sources in molecular species in the sky, can also be used as a state-of-the-art spectroscopy laboratory in the millimeter and submillimeter domains.
- ID:
- ivo://CDS.VizieR/J/A+A/574/A56
- Title:
- IRC +10216 17.8GHz-26.3GHz spectrum
- Short Name:
- J/A+A/574/A56
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- IRC +10216 is the prototypical carbon star exhibiting an extended molecular circumstellar envelope. Its spectral properties are therefore the template for an entire class of objects. The main goal is to systematically study the 1.3cm spectral line characteristics of IRC +10216. We carried out a spectral line survey with the Effelsberg-100m telescope toward IRC +10216. It covers the frequency range between 17.8GHz and 26.3GHz (K-band). In the circumstellar shell of IRC +10216, we find 78 spectral lines, among which 12 remain unidentified. The identified lines are assigned to 18 different molecules and radicals. A total of 23 lines from species known to exist in this envelope are detected for the first time outside the Solar System and there are additional 20 lines firstly detected in IRC +10216. The potential orgin of U lines is also discussed. Assuming local thermodynamic equilibrium (LTE), we determine rotational temperatures and column densities of 17 detected molecules. Molecular abundances relative to H_2_ are also estimated. A non-LTE analysis of NH_3_ shows that the bulk of its emission arises from the inner envelope with a kinetic temperature of 70+/-20K. Evidence for NH_3_ emitting gas with higher kinetic temperature is also obtained, and potential abundance differences between various ^13^C-bearing isotopologues of HC_5_N are evaluated. Overall, the isotopic ^12^C/^13^C ratio is estimated to be 49+/-9. Finally, a comparison of detected molecules in the 1.3cm range with the dark cloud TMC-1 indicates that silicate bearing molecules are more predominant in IRC +10216.
- ID:
- ivo://CDS.VizieR/J/A+A/606/A74
- Title:
- IRC +10216 13.3GHz-18.5GHz spectrum
- Short Name:
- J/A+A/606/A74
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A spectral line survey of IRC +10216 between 13.3 and 18.5GHz was carried out using the Shanghai Tian Ma 65 m Radio Telescope (TMRT-65m) with a sensitivity of <7mK. Thirty-five spectral lines of 12 different molecules and radicals were detected in total. Except for SiS, the detected molecules are all carbon-chain molecules, including HC_3_N, HC_5_N, HC_7_N, HC_9_N, C_6_H, C_6_H^-^, C_8_H, SiC_2_, SiC_4_, c-C_3_H_2_, and l-C_5_H. The presence of rich carbon-bearing molecules is consistent with the identity of IRC +10216 as a carbon-rich asymptotic giant branch (AGB) star. The excitation temperatures and column densities of the observed species are derived by assuming a local thermodynamic equilibrium and homogeneous conditions.
- ID:
- ivo://CDS.VizieR/J/A+A/639/A61
- Title:
- IR continuum, [CII] and [OI] maps of M33
- Short Name:
- J/A+A/639/A61
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- M33 is a gas rich spiral galaxy of the Local Group. Its vicinity allows us to study its interstellar medium (ISM) on linear scales corresponding to the sizes of individual giant molecular clouds. We investigate the relationship between the two major gas cooling lines and the total infrared (TIR) dust continuum. We mapped the emission of gas and dust in M33 using the far-infrared lines of [CII] and [OI](63um) and the total infrared continuum. The line maps were observed with the PACS spectrometer on board the Herschel Space Observatory. These maps have 50pc resolution and form a ~370pc wide stripe along its major axis covering the sites of bright HII regions, but also more quiescent arm and inter-arm regions from the southern arm at 2kpc galacto-centric distance to the south out to 5.7kpc distance to the north. Full-galaxy maps of the continuum emission at 24um from Spitzer/MIPS, and at 70um, 100um, and 160um from Herschel/PACS were combined to obtain a map of the TIR. TIR and [CII] intensities are correlated over more than two orders of magnitude. The range of TIR translates to a range of far ultraviolet (FUV) emission of G_0,obs_~2 to 200 in units of the average Galactic radiation field. The binned [CII]/TIR ratio drops with rising TIR, with large, but decreasing scatter. The contribution of the cold neutral medium to the [CII] emission, as estimated from VLA HI data, is on average only 10%. Fits of modified black bodies (MBBs) to the continuum emission were used to estimate dust mass surface densities and total gas column densities. A correction for possible foreground absorption by cold gas was applied to the [OI] data before comparing it with models of photon dominated regions (PDRs). Most of the ratios of [CII]/[OI] and ([CII]+[OI])/TIR are consistent with two model solutions. The median ratios are consistent with one solution at n~2x10^2^cm^-3^, G_0_~60, and and a second low-FUV solution at n~10^4^cm^-3^, G_0_~1.5. The bulk of the gas along the lines-of-sight is represented by a low-density, high-FUV phase with low beam filling factors ~1. A fraction of the gas may, however, be represented by the second solution.
- ID:
- ivo://CDS.VizieR/J/AJ/162/82
- Title:
- IRD and HPF spectra of TRAPPIST-1b,e and f
- Short Name:
- J/AJ/162/82
- Date:
- 11 Mar 2022
- Publisher:
- CDS
- Description:
- We obtained high-resolution spectra of the ultracool M-dwarf TRAPPIST-1 during the transit of its planet "b" using two high-dispersion near-infrared spectrographs, the Infrared Doppler (IRD) instrument on the Subaru 8.2m telescope, and the Habitable Zone Planet Finder (HPF) instrument on the 10m Hobby-Eberly Telescope. These spectroscopic observations are complemented by a photometric transit observation for planet "b" using the APO/ARCTIC, which assisted us in capturing the correct transit times for our transit spectroscopy. Using the data obtained by the new IRD and HPF observations, as well as the prior transit observations of planets "b," "e" and "f" from IRD, we attempt to constrain the atmospheric escape of the planet using the Hei triplet 10830{AA} absorption line. We do not detect evidence for any primordial extended H-He atmospheres in all three planets. To limit any planet-related absorption, we place an upper limit on the equivalent widths of <7.754m{AA} for planet "b," <10.458m{AA} for planet "e," <4.143m{AA} for planet "f" at 95% confidence from the IRD data, and <3.467m{AA} for planet "b" at 95% confidence from HPF data. Using these limits along with a solar- like composition isothermal Parker wind model, we attempt to constrain the mass-loss rates for the three planets. For TRAPPIST-1b, our models exclude the highest possible energy-limited rate for a wind temperature <5000K. This nondetection of extended atmospheres with low mean-molecular weights in all three planets aids in further constraining their atmospheric composition by steering the focus toward the search of high-molecular-weight species in their atmospheres.
- ID:
- ivo://CDS.VizieR/J/A+A/603/A22
- Title:
- IRDCs cores spectra of HCN and HNC isotopologue
- Short Name:
- J/A+A/603/A22
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of the measurement of nitrogen fractionation in a sample of infrared-dark clouds (IRDCs) cores which are believed to be the precursors of high-mass stars and star clusters. We observed the J=1-0 transitions of HCN, H^13/^CN, HC^15/^N, HN^13/^C, and H^15/^NC towards a sample of 22 cores in four IRDCs using the IRAM 30m telescope.Assuming LTE and a temperature of 15K, the 14N/^15/^N ratios measured are consistent with the terrestrial atmosphere(TA) and protosolar nebula(PSN) values, and with the ratios measured in low-mass prestellar cores. However, the 14N/^15/^N ratios measured in cores C1, C3, F1, F2, and G2 do not agree with the results from similar studies towards the same cores using nitrogen bearing molecules with nitrile functional group(-CN) and nitrogen hydrides (-NH) although the ratio spread covers a similar range. Relatively low 14N/^15/^N ratios amongst the four-IRDCs were measured in IRDC G which are comparable to those measured in small cosmomaterials and protoplanetary disks. The low average gas density of this cloud suggests that the gas density, rather than the gas temperature, may be the dominant parameter influencing the initial nitrogen isotopic composition in young PSN.
- ID:
- ivo://CDS.VizieR/J/ApJ/900/104
- Title:
- IR high-res. sp. of hot cores of AFGL2591 & AFGL2136
- Short Name:
- J/ApJ/900/104
- Date:
- 21 Mar 2022 09:36:08
- Publisher:
- CDS
- Description:
- We have performed a high-resolution 4-13{mu}m spectral survey of the hot molecular gas associated with the massive protostars AFGL 2591 and AFGL 2136, utilizing the Echelon Cross Echelle Spectrograph (EXES) on board the Stratospheric Observatory for Infrared Astronomy, and the iSHELL instrument and Texas EchelonCross Echelle Spectrograph (TEXES) on the NASA Infrared Telescope Facility (IRTF). Here we present the results of this survey with analysis of CO, HCN, C2H2, NH3, and CS, deriving the physical conditions for each species. Also from the IRTF, iSHELL data at 3{mu}m for AFGL 2591 are presented that show HCN and C2H2 in emission. In the EXES and TEXES data, all species are detected in absorption, and temperatures and abundances are found to be high (600K and 10^-6^, respectively). Differences of up to an order of magnitude in the abundances of transitions that trace the same ground-state level are measured for HCN and C2H2. The mid-infrared continuum is known to originate in a disk, hence we attribute the infrared absorption to arise in the photosphere of the disk. As absorption lines require an outwardly decreasing temperature gradient, we conclude that the disk is heated in the midplane by viscous heating due to accretion. We attribute the near-IR emission lines to scattering by molecules in the upper layers of the disk photosphere. The absorption lines trace the disk properties at 50 au where high-temperature gas-phase chemistry is taking place. Abundances are consistent with chemical models of the inner disk of Herbig disks.
- ID:
- ivo://CDS.VizieR/J/AJ/144/11
- Title:
- IR imaging, nuclear SEDs, Spitzer spectra of 22 AGNs
- Short Name:
- J/AJ/144/11
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present high-resolution mid-infrared (MIR) imaging, nuclear spectral energy distributions (SEDs), and archival Spitzer spectra for 22 low-luminosity active galactic nuclei (LLAGNs; L_bol_<~10^42^erg/s). Infrared (IR) observations may advance our understanding of the accretion flows in LLAGNs, the fate of the obscuring torus at low accretion rates, and, perhaps, the star formation histories of these objects. However, while comprehensively studied in higher-luminosity Seyferts and quasars, the nuclear IR properties of LLAGNs have not yet been well determined. We separate the present LLAGN sample into three categories depending on their Eddington ratio and radio emission, finding different IR characteristics for each class. (1) At the low-luminosity, low-Eddington-ratio (log L_bol_/L_Edd_< -4.6) end of the sample, we identify "host-dominated" galaxies with strong polycyclic aromatic hydrocarbon bands that may indicate active (circum-)nuclear star formation. (2) Some very radio-loud objects are also present at these low Eddington ratios. The IR emission in these nuclei is dominated by synchrotron radiation, and some are likely to be unobscured type 2 AGNs that genuinely lack a broad-line region. (3) At higher Eddington ratios, strong, compact nuclear sources are visible in the MIR images. The nuclear SEDs of these galaxies are diverse; some resemble typical Seyfert nuclei, while others lack a well-defined MIR "dust bump." Strong silicate emission is present in many of these objects. We speculate that this, together with high ratios of silicate strength to hydrogen column density, could suggest optically thin dust and low dust-to-gas ratios, in accordance with model predictions that LLAGNs do not host a Seyfert-like obscuring torus. We anticipate that detailed modeling of the new data and SEDs in terms of accretion disk, jet, radiatively inefficient accretion flow, and torus components will provide further insights into the nuclear structures and processes of LLAGNs.
- ID:
- ivo://CDS.VizieR/J/ApJ/723/895
- Title:
- IR luminosities and aromatic features of 5MUSES
- Short Name:
- J/ApJ/723/895
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study a 24um selected sample of 330 galaxies observed with the infrared spectrograph for the 5mJy Unbiased Spitzer Extragalactic Survey (5MUSES). We estimate accurate total infrared luminosities by combining mid-IR spectroscopy and mid-to-far infrared photometry, and by utilizing new empirical spectral templates from Spitzer data. The infrared luminosities of this sample range mostly from 10^9^L_{sun}_ to 10^13.5^L_{sun}_, with 83% in the range 10^10^L_{sun}_<L_IR_<10^12^L_{sun}_. The redshifts range from 0.008 to 4.27, with a median of 0.144. The equivalent widths of the 6.2um aromatic feature have a bimodal distribution, probably related to selection effects. We use the 6.2um polycyclic aromatic hydrocarbon equivalent width (PAH EW) to classify our objects as starburst (SB)-dominated (44%), SB-AGN composite (22%), and active galactic nucleus (AGN)-dominated (34%). The high EW objects (SB-dominated) tend to have steeper mid-IR to far-IR spectral slopes and lower LIR and redshifts.
