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- ID:
- ivo://CDS.VizieR/J/A+A/643/A91
- Title:
- ArH+ and p-H2O+ spectra towards 7 molecular clouds
- Short Name:
- J/A+A/643/A91
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- One of the surprises of the Herschel mission was the detection of ArH+, toward the Crab Nebula in emission and in absorption toward strong Galactic background sources. Although, these detections were limited to the first quadrant of the Galaxy, the existing data suggests that ArH+ ubiquitously and exclusively probes the diffuse atomic regions of the interstellar medium. In this study we extend the coverage of ArH+ to other parts of the Galaxy with new observations of its J=1-0 transition along seven Galactic sight lines toward bright sub-millimetre continuum sources. We aim to benchmark its efficiency as a tracer of purely atomic gas by evaluating its correlation (or lack of correlation as suggested by chemical models) with other well known atomic gas tracers like OH+ and H_2_O+ and the molecular gas tracer CH. The observations of the J=1-0 line of ArH+ near 617.5GHz were made feasible with the new, sensitive SEPIA660 receiver on the APEX 12m telescope. Further, the two sidebands of this receiver allowed us to observe the N_KaKc_=1_1,0_-1_0,1_ transitions of para-H_2_O+ at 607.227GHz simultaneously with the ArH+ line. We model the optically thin absorption spectra of the different species and subsequently derived their column densities. By analysing the steady state chemistry of OH+ and o-H_2_O+ we derive on average a cosmic-ray ionisation rate of 2.3+/-0.3x10^-16^s^-1^, toward the sightlines studied in this work. Using the derived values of the cosmic-ray ionisation rates and the observed ArH+ abundances we constrain the molecular fraction of the gas traced by ArH+ to lie below 2x10^-2^ with a median value of 8.8x10^-4^. Combined, our observations of ArH+, OH+, H_2_O+ and CH probe different regimes of the interstellar medium, from diffuse atomic to diffuse and translucent molecular clouds. Over Galactic scales, we see that the distribution of N(ArH+) is associated with that of N(H), particularly in the inner Galaxy (within 7 kpc of the Galactic center) with potentially even contributions from the warm neutral medium phase of atomic gas at larger galactocentric distances. We derive an average ortho-to-para ratio for H_2_O+ of 2.1+/-1.0, which corresponds to a nuclear spin temperature of 41K, consistent with the typical gas temperatures of diffuse clouds.
- ID:
- ivo://CDS.VizieR/J/A+A/631/A86
- Title:
- ArH+ by collision with He
- Short Name:
- J/A+A/631/A86
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The study of noble gas compounds has gained renewed interest thanks to the recent detection of ArH^+^ in the interstellar medium (ISM). The analysis of physical-chemical conditions in the regions of the ISM where ArH^+^ is observed requires accurate collisional data of ArH^+^ with He, H_2_, electrons, and H. The main goals of this work are to compute the first three-dimensional potential energy surface (PES) to study the interaction of ArH^+^ with He, analyze the influence of the isotopic effects in the rate coefficients, and evaluate the rovibrational relaxation rates. Two ab initio grids of energy were computed at the coupled cluster with single, double, and perturbative triple excitations (CCSD(T)) level of theory using the augmented correlation consistent polarized quadruple, and quintuple zeta basis sets (aug-cc-pVQZ, and aug-cc-pV5Z) and a grid at the complete basis set limit was determined. The analytical representation of the PES was performed using the reproducing kernel Hilbert space (RKHS). The dynamics of the system was studied using the close coupling method. The differences in the rate coefficients for the isotopes ^36^ArH^+^, ^38^ArH^+^, and ^40^ArH^+^ in collision with He are negligible. However, the rotational rates for the collision of ArD+ with He cannot be estimated from those for ArH^+^+He. Comparison with previous rates for the 36ArH++He collision showed discrepancies for |{Delta}j|>2, and in the case of high initial rotational states of 36ArH+ differences were found even for |{Delta}j|=1. The rates for transitions between different vibrational states were also examined. Finally, new sets of rotational rates for ^36^ArH^+^+He and ^36^ArD^+^+He are reported.
- ID:
- ivo://CDS.VizieR/J/MNRAS/425/2116
- Title:
- Arizona CDFS Environment Survey, ACES
- Short Name:
- J/MNRAS/425/2116
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the Arizona CDFS Environment Survey (ACES), a recently completed spectroscopic redshift survey of the Chandra Deep Field-South (CDFS) conducted using the Inamori-Magellan Areal Camera and Spectrograph on the Magellan-Baade telescope. In total, the survey targeted 7277 unique sources down to a limiting magnitude of R_AB_=24.1, yielding 5080 secure redshifts across the ~30'x30' extended CDFS region. The ACES data set delivers a significant increase to both the spatial coverage and the sampling density of the spectroscopic observations in the field. Combined with previously published spectroscopic redshifts, ACES now creates a highly complete survey of the galaxy population at R<23, enabling the local galaxy density (or environment) on relatively small scales (~1Mpc) to be measured at z<1 in one of the most heavily studied and data-rich fields in the sky. Here, we describe the motivation, design and implementation of the survey and present a preliminary redshift and environment catalogue. In addition, we utilize the ACES spectroscopic redshift catalogue to assess the quality of photometric redshifts from both the COMBO-17 and Multiwavelength Survey by Yale-Chile imaging surveys of the CDFS.
- ID:
- ivo://CDS.VizieR/J/AJ/129/2798
- Title:
- AR Mon photometry and radial velocities
- Short Name:
- J/AJ/129/2798
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- New differential UBV photoelectric photometry and echelle spectroscopy for the eclipsing binary AR Mon are presented. A total of 46 radial velocities for each component are obtained using the TODCOR procedure. We solve the new and previously published multicolor light curves simultaneously with the new radial velocities using the latest version of the Wilson-Devinney program. We confirm that AR Mon is a semidetached binary consisting of two evolved giant stars and is a member of the rare class of "cool Algols".
- ID:
- ivo://CDS.VizieR/J/ApJ/715/506
- Title:
- Aromatic inventory of the local volume
- Short Name:
- J/ApJ/715/506
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using infrared photometry from the Spitzer Space Telescope, we perform the first inventory of aromatic feature emission (also commonly referred to as polycyclic aromatic hydrocarbon emission) for a statistically complete sample of star-forming galaxies in the local volume. The photometric methodology involved is calibrated and demonstrated to recover the aromatic fraction of the Infrared Array Camera 8um flux with a standard deviation of 6% for a training set of 40 SINGS galaxies (ranging from stellar to dust dominated; Kennicutt et al. 2003PASP..115..928K) with both suitable mid-infrared Spitzer Infrared Spectrograph spectra and equivalent photometry. A potential factor of 2 improvement could be realized with suitable 5.5um and 10um photometry, such as what may be provided in the future by the James Webb Space Telescope. The resulting technique is then applied to mid-infrared photometry for the 258 galaxies from the Local Volume Legacy (LVL; Dale et al. 2009, Cat. J/ApJ/703/517) survey, a large sample dominated in number by low-luminosity dwarf galaxies for which obtaining comparable mid-infrared spectroscopy is not feasible. Using oxygen abundances compiled from the literature for 129 of the 258 LVL galaxies, we find a correlation between metallicity and the aromatic-to-total infrared emission ratio but not the aromatic-to-total 8um dust emission ratio. A possible explanation is that metallicity plays a role in the abundance of aromatic molecules relative to the total dust content, but other factors, such as star formation and/or the local radiation field, affect the excitation of those molecules.
- ID:
- ivo://CDS.VizieR/J/A+AS/136/81
- Title:
- A ROSAT PSPC X-Ray Survey of the SMC
- Short Name:
- J/A+AS/136/81
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a systematic search for point-like and moderately extended soft (0.1-2.4keV) X-ray sources in a raster of nine pointings covering a field of 8.95deg^2^ and performed with the ROSAT PSPC between October 1991 and October 1993 in the direction of the Small Magellanic Cloud (SMC). We detect 248 objects which we include in the first version of our SMC catalogue of soft X-ray sources. We set up seven source classes defined by selections in the count rate, hardness ratio and source extent. We find five high luminosity super-soft sources (1E 0035.4-7230, 1E 0056.8-7146, RX J0048.4-7332, RX J0058.6-7146 and RX J0103-7254), one low-luminosity super-soft source RX J0059.6-7138 correlating with the planetary nebula L357, 51 candidate hard X-ray binaries including eight bright hard X-ray binary candidates, 19 supernova remnants (SNRs), 19 candidate foreground stars and 53 candidate background active galactic nuclei (and quasars). We give a likely classification for ~60% of the catalogued sources. The total count rate of the detected point-like and moderately extended sources in our catalogue is 6.9+/-0.3s^-1, comparable to the background subtracted total rate from the integrated field of ~6.1+/-0.1s^-1.
- ID:
- ivo://CDS.VizieR/J/AJ/131/633
- Title:
- A ROSAT survey of contact binary stars
- Short Name:
- J/AJ/131/633
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Contact binary stars are common variable stars that are all believed to emit relatively large fluxes of X-rays. In this work we combine a large new sample of contact binary stars derived from the ROTSE-I telescope (Cat. <J/AJ/131/621>) with X-ray data from the ROSAT All Sky Survey (RASS, Cat. <IX/10>) to estimate the X-ray volume emissivity of contact binary stars in the Galaxy. We obtained X-ray fluxes for 140 contact binaries from the RASS, as well as two additional stars observed by the XMM-Newton observatory.
1099. Arp 2
- ID:
- ivo://CDS.VizieR/J/AJ/109/650
- Title:
- Arp 2
- Short Name:
- J/AJ/109/650
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have obtained the first B,V CCD color-magnitude diagram (CMD) of the galactic globular cluster Arp 2. About 1600 stars have been measured between the tip of the red giant branch at V ~ 15.5 and V ~ 23.5, about two magnitudes below the main sequence turnoff. A centrally concentrated population of blue stragglers has been detected. The slope of the red giant branch and the overall CMD morphology are consistent with that of a metal-poor cluster, with [Fe/H] = 18.4+/-0.25. A preliminary spectroscopic measurement based on the Ca II triplet yields [Fe/H] = -1.73+/-0.05. The comparison of the CMD of Arp 2 with that of other clusters favors a value more metal-poor than that indicated by the Ca II triplet. In this respect, Arp 2 is similar to Ruprecht 106 [Buonanno et al. =1990AJ....100.1811B and =1993AJ....105..184B]. Differential ages between Arp 2 and a number of reference clusters are obtained from the vertical age parameter Delta V^TO_HB, and the horizontal age parameter, {Delta}(B-V)^TO_RGB. By requiring both age estimators to give consistent results, we find that Arp 2 is ~ 3 Gyr younger than the group of the metal-poor clusters and slightly older than Ruprecht 106. The detection of young metal-poor clusters ([Fe/H] <= -1.8) implies a complex scenario for the origin of the galactic halo, possibly involving interactions with satellite galaxies and their cluster systems.
- ID:
- ivo://CDS.VizieR/J/ApJ/799/10
- Title:
- Arp 220 6 and 33GHz images
- Short Name:
- J/ApJ/799/10
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new Karl G. Jansky Very Large Array radio continuum images of the nuclei of Arp 220, the nearest ultra-luminous infrared galaxy. These new images have both the angular resolution to study the detailed morphologies of the two nuclei that power the galaxy merger and sensitivity to a wide range of spatial scales. At 33GHz, we achieve a resolution of 0.081"x0.063" (29.9x23.3pc) and resolve the radio emission surrounding both nuclei. We conclude from the decomposition of the radio spectral energy distribution that a majority of the 33GHz emission is synchrotron radiation. The spatial distributions of radio emission in both nuclei are well described by exponential profiles. These have deconvolved half-light radii (R_50d_) of 51 and 35pc for the eastern and western nuclei, respectively, and they match the number density profile of radio supernovae observed with very long baseline interferometry. This similarity might be due to the fast cooling of cosmic rays electrons caused by the presence of a strong (~mG) magnetic field in this system. We estimate extremely high molecular gas surface densities of 2.2_-1.0_^+2.1^x10^5^M_{sun}_/pc^2^ (east) and 4.5_-1.9_^+4.5^x10^5^M_{sun}_/pc^2^ (west), corresponding to total hydrogen column densities of N_H_=2.7_-1.2_^+2.7^x10^25^cm^-2^ (east) and 5.6_-2.4_^+5.5^x10^25^cm^-2^ (west). The implied gas volume densities are similarly high, n_H2_~3.8_-1.6_^+3.8^x10^4^cm^-3^ (east) and ~11_-4.5_^+12^x10^4^cm^-3^ (west). We also estimate very high luminosity surface densities of {Sigma}_IR_~4.2_-0.7_^+1.6^x10^13^L_{sun}_/kpc^2^ (east) and {Sigma}_IR_ ~ 9.7_-2.4_^+3.7^x10^13^_L_{sun}/kpc^2^ (west), and star formation rate surface densities of {Sigma}_SFR_~10^3.7+/-0.1^M_{sun}_/yr/kpc^2^ (east) and {Sigma}_SFR_~10^4.1+/-0.1^M_{sun}_/yr/kpc^2^ (west). These values, especially for the western nucleus are, to our knowledge, the highest luminosity surface densities and star formation rate surface densities measured for any star-forming system. Despite these high values, the nuclei appear to lie below the dusty Eddington limit in which radiation pressure is balanced only by self-gravity. The small measured sizes also imply that at wavelengths shorter than {lambda}=1mm, dust absorption effects must play an important role in the observed light distribution while below 5GHz free-free absorption contributes substantial opacity. According to these calculations, the nuclei of Arp 220 are only transparent in the frequency range ~5-350GHz. Our results offer no clear evidence that an active galactic nucleus dominates the emission from either nucleus at 33GHz.
