- ID:
- ivo://CDS.VizieR/J/ApJ/866/L1
- Title:
- Dust models & IR spectroscopy obs. of AGB stars
- Short Name:
- J/ApJ/866/L1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Many emission features remain unidentified in the infrared spectra of asymptotic giant branch (AGB) stars. In particular, features at ~11, 20, 28, and 32{mu}m have been noted in mid-infrared spectra of oxygen-rich AGB stars. Here, I present models of dust excess emission in 36 spectra of 24 AGB stars from the Short Wavelength Spectrometer on board the Infrared Space Observatory and the Infrared Spectrograph on the Spitzer Space Telescope. The models include opacities of grains composed of mixtures of various polymorphs of alumina obtained by preparing bayerite and boehmite at high temperatures, and these dust components provide satisfactory fits to the 11, 20, 28, and 32{mu}m features. Though not a direct conclusion from this study, the presence of grains of the various polymorphs of aluminas in circumstellar dust shells around AGB stars suggests that corundum may have a role in giving rise to the 13{mu}m feature.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/641/A44
- Title:
- Dwarfs, giants and supergiants Equivalent widths
- Short Name:
- J/A+A/641/A44
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Stellar population studies in the infrared (IR) wavelength range have two main advantages with respect to the optical regime: they probe different populations, because most of the light in the IR comes from redder and generally older stars and allow us to see through dust because the IR light is less affected by extinction. Our project investigates the sensitivity of various spectral features in the 1-5um wavelength range to the physical properties of stars (Teff, [Fe/H], logg) and aims to objectively define spectral indices that can characterize age and metallicity of unresolved stellar populations. We implemented a method that uses derivatives of the indices as functions of Teff, [Fe/H] of log g across the entire available wavelength range to reveal the most sensitive indices to these parameters and the ranges in which these indices work. Here, we complement the previous work in the I and K bands reporting a new system for Y, J, H and L atmospheric windows. We list the equivalent widths of these indices for the Infrared Telescope Facility (IRTF) spectral library stars.
- ID:
- ivo://CDS.VizieR/J/ApJ/771/85
- Title:
- Dynamical masses of z~2 quiescent galaxies
- Short Name:
- J/ApJ/771/85
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using stellar kinematics measurements, we investigate the growth of massive, quiescent galaxies from z~2 to today. We present X-Shooter spectra from the UV to NIR and dynamical mass measurements of five quiescent massive (>10^11^M_{sun}_) galaxies at z~2. This triples the sample of z>1.5 galaxies with well-constrained ({delta}{sigma}<100km/s) velocity dispersion measurements. From spectral population synthesis modeling we find that these galaxies have stellar ages that range from 0.5 to 2Gyr, with no signs of ongoing star formation. We measure velocity dispersions (290-450km/s) from stellar absorption lines and find that they are 1.6-2.1 times higher than those of galaxies in the Sloan Digital Sky Survey at the same mass. Sizes are measured using GALFIT from Hubble Space Telescope Wide Field Camera 3 H_160_ and UDS K-band images. The dynamical masses correspond well to the spectral energy distribution based stellar masses, with dynamical masses that are ~15% higher.
- ID:
- ivo://CDS.VizieR/J/ApJ/715/310
- Title:
- Early stages of star formation in IRDCs
- Short Name:
- J/ApJ/715/310
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Identified as extinction features against the bright Galactic mid-infrared background, infrared dark clouds (IRDCs) are thought to harbor the very earliest stages of star and cluster formation. In order to better characterize the properties of their embedded cores, we have obtained new 24um, 60-100um, and submillimeter continuum data toward a sample of 38 IRDCs. The 24um Spitzer images reveal that while the IRDCs remain dark, many of the cores are associated with bright 24um emission sources, which suggests that they contain one or more embedded protostars. Combining the 24um, 60-100um, and submillimeter continuum data, we have constructed broadband spectral energy distributions (SEDs) for 157 of the cores within these IRDCs and, using simple graybody fits to the SEDs, have estimated their dust temperatures, emissivities, opacities, bolometric luminosities, masses, and densities. Based on their Spitzer/Infrared Array Camera 3-8um colors and the presence of 24um point-source emission, we have separated cores that harbor active, high-mass star formation from cores that are quiescent. The active "protostellar" cores typically have warmer dust temperatures and higher bolometric luminosities than the more quiescent, perhaps "pre-protostellar," cores. Because the mass distributions of the populations are similar, however, we speculate that the active and quiescent cores may represent different evolutionary stages of the same underlying population of cores. Although we cannot rule out low-mass star formation in the quiescent cores, the most massive of them are excellent candidates for the "high-mass starless core" phase, the very earliest in the formation of a high-mass star.
- ID:
- ivo://CDS.VizieR/J/MNRAS/436/3759
- Title:
- ECDFS sources optical/IR counterparts
- Short Name:
- J/MNRAS/436/3759
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The sub-mJy radio population is a mixture of active systems, that is star-forming galaxies (SFGs) and active galactic nuclei (AGNs). We study a sample of 883 radio sources detected at 1.4GHz in a deep Very Large Array survey of the Extended Chandra Deep Field-South that reaches a best rms sensitivity of 6{mu}Jy. We have used a simple scheme to disentangle SFGs, radio-quiet (RQ), and radio-loud (RL) AGNs based on the combination of radio data with Chandra X-ray data and mid-infrared observations from Spitzer. We find that at flux densities between about 30 and 100{mu}Jy, the radio population is dominated by SFGs (~60%) and that RQ AGNs become increasingly important over RL ones below 100 {mu}Jy. We also compare the host galaxy properties of the three classes in terms of morphology, optical colours and stellar masses. Our results show that both SFG and RQ AGN host galaxies have blue colours and late-type morphology while RL AGNs tend to be hosted by massive red galaxies with early-type morphology. This supports the hypothesis that radio emission in SFGs and RQ AGNs mainly comes from the same physical process: star formation in the host galaxy.
- ID:
- ivo://CDS.VizieR/J/ApJ/879/105
- Title:
- Effective temperatures of low-mass stars
- Short Name:
- J/ApJ/879/105
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- High-resolution, near-infrared spectra will be the primary tool for finding and characterizing Earth-like planets around low-mass stars. Yet, the properties of exoplanets cannot be precisely determined without accurate and precise measurements of the host star. Spectra obtained with the Immersion Grating Infrared Spectrometer simultaneously provide diagnostics for most stellar parameters, but the first step in any analysis is the determination of the effective temperature. Here we report the calibration of high-resolution H-band spectra to accurately determine the effective temperature for stars between 4000 and 3000K (~K8-M5) using absorption line-depths of FeI, OH, and Al I. The field star sample used here contains 254 K and M stars with temperatures derived using BT-Settl synthetic spectra. We use 106 stars with precise temperatures in the literature to calibrate our method, with typical errors of about 140K, and systematic uncertainties less than ~120K. For the broadest applicability, we present Teff-line-depth-ratio relationships, which we test on 12 members of the TW Hydrae Association and at spectral resolving powers between ~10000 and 120000. These ratios offer a simple but accurate measure of effective temperatures in cool stars that are distance and reddening independent.
- ID:
- ivo://CDS.VizieR/J/A+A/456/881
- Title:
- EIS: infrared deep public survey
- Short Name:
- J/A+A/456/881
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper is part of the series presenting the final results obtained by the ESO Imaging Survey (EIS) project. It presents new J and Ks data obtained from observations conducted at the ESO 3.5m New Technology Telescope (NTT) using the SOFI camera. These data were taken as part of the Deep Public Survey (DPS) carried out by the ESO Imaging Survey program, significantly extending the earlier optical/infrared EIS-DEEP survey presented in a previous paper of this series. The DPS-IR survey comprises two observing strategies: shallow Ks observations providing nearly full coverage of pointings with complementary multi-band (in general UBVRI) optical data obtained using ESO's wide-field imager (WFI) and deeper J and Ks observations of the central parts of these fields. Currently, the DPS-IR survey provides a coverage of roughly 2.1 square degrees (~300 SOFI pointings) in Ks with 0.63 square degrees to fainter magnitudes and also covered in J, over three independent regions of the sky. The goal of the present paper is to briefly describe the observations, the data reduction procedures, and to present the final survey products which include fully calibrated pixel-maps and catalogs extracted from them. The astrometric solution with an estimated accuracy of <0.15" is based on the USNO catalog and limited only by the accuracy of the reference catalog. The final stacked images presented here number 89 and 272, in J and Ks, respectively, the latter reflecting the larger surveyed area. The J and Ks images were taken with a median seeing of 0.7" and 0.8". The images reach a median 5 sigma limiting magnitude of J_AB~23.06 as measured within an aperture of 2", while the corresponding limiting magnitude in Ks_AB is ~21.41 and ~22.16mag for the shallow and deep strategies. Although some spatial variation due to varying observing conditions is observed, overall the observed limiting magnitudes are consistent with those originally proposed. The quality of the data has been assessed by comparing the measured magnitude of sources at the bright end directly with those reported by the 2MASS survey and at the faint end by comparing the counts of galaxies and stars with those of other surveys to comparable depth and to model predictions. The final science-grade catalogs together with the astrometrically and photometrically calibrated co-added images are available at CDS.
- ID:
- ivo://CDS.VizieR/J/A+A/452/119
- Title:
- EIS: infrared observations of CDF-S and HDF-S
- Short Name:
- J/A+A/452/119
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper presents infrared data obtained from observations carried out at the ESO 3.5m New Technology Telescope (NTT) of the Hubble Deep Field South (HDF-S) and the Chandra Deep Field South (CDF-S). These data were taken as part of the ESO Imaging Survey (EIS) program, a public survey conducted by ESO to promote follow-up observations with the VLT. In the HDF-S field the infrared observations cover an area of ~53 square arcmin, encompassing the HST WFPC2 and STIS fields, in the JHKs passbands. The seeing measured in the final stacked images ranges from 0.79" to 1.22" and the median limiting magnitudes (AB system, 2" aperture, 5sigma detection limit) are J_AB~23.0, H_AB~22.8 and K_AB~23.0mag. Less complete data are also available in JKs for the adjacent HST NICMOS field. For CDF-S, the infrared observations cover a total area of ~100 square arcmin, reaching median limiting magnitudes (as defined above) of J_AB~23.6 and K_AB~22.7mag. For one CDF-S field H-band data are also available. This paper describes the observations and presents the results of new reductions carried out entirely through the un-supervised, high-throughput EIS Data Reduction System and its associated EIS/MVM C++-based image processing library developed, over the past 5 years, by the EIS project and now publicly available. The paper also presents source catalogs extracted from the final co-added images which are used to evaluate the scientific quality of the survey products, and hence the performance of the software. This is done comparing the results obtained in the present work with those obtained by other authors from independent data and/or reductions carried out with different software packages and techniques.
- ID:
- ivo://CDS.VizieR/J/MNRAS/358/333
- Title:
- ELAIS optical ident. at 15um & 1.4GHz
- Short Name:
- J/MNRAS/358/333
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the multi-wavelength properties and catalogue of the 15{mu}m and 1.4GHz radio sources detected in the European Large Area ISO Survey (ELAIS) areas N1 and N2. Using the optical data from the Wide Field Survey we use a likelihood ratio method to search for the counterparts of the 1056 and 691 sources detected at 15{mu}m and 1.4GHz, respectively, down to flux limits of S_15_=0.5mJy and S_1.4_GHz=0.135mJy.
- ID:
- ivo://CDS.VizieR/J/ApJ/772/48
- Title:
- Emission-line galaxies from PEARS. II.
- Short Name:
- J/ApJ/772/48
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a full analysis of the Probing Evolution And Reionization Spectroscopically (PEARS) slitess grism spectroscopic data obtained with the Advanced Camera for Surveys on board Hubble Space Telescope. PEARS covers fields within both the Great Observatories Origins Deep Survey (GOODS) North and South fields, making it ideal as a random survey of galaxies, as well as the availability of a wide variety of ancillary observations complemented by the spectroscopic results. Using the PEARS data, we are able to identify star-forming galaxies (SFGs) within the redshift volume 0<z<1.5. Star-forming regions in the PEARS survey are pinpointed independently of the host galaxy. This method allows us to detect the presence of multiple emission-line regions (ELRs) within a single galaxy. We identified a total of 1162 H{alpha}, [OIII], and/or [OII] emission lines in the PEARS sample of 906 galaxies to a limiting flux of ~10^-18^erg/s/cm2. The ELRs have also been compared to the properties of the host galaxy, including morphology, luminosity, and mass. From this analysis, we find three key results: (1) the computed line luminosities show evidence of a flattening in the luminosity function with increasing redshift; (2) the star-forming systems show evidence of complex morphologies with star formation occurring predominantly within one effective (half-light) radius. However, the morphologies show no correlation with host stellar mass. (3) Also, the number density of SFGs with M_*_>=10^9^M_{sun}_ decreases by an order of magnitude at z<=0.5 relative to the number at 0.5<z<0.9, supporting the argument of galaxy downsizing.
