- ID:
- ivo://CDS.VizieR/J/A+A/610/A10
- Title:
- Sgr B2 los molecular absorption line spectra
- Short Name:
- J/A+A/610/A10
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The 1-50 GHz PRebiotic Interstellar MOlecular Survey (PRIMOS) contains >50 molecular absorption lines observed in clouds located in the line-of-sight to Sgr B2(N). The line-of- sight material is associated with diffuse and translucent clouds located in the Galactic Center, Bar, and spiral arms in the disk. We measure the column densities and estimate abundances, relative to H_2_, of 11 molecules and additional isotopologues observed in this material. We use absorption by optically thin transitions of c-C_3_H_2_ to estimate the molecular hydrogen columns, and argue that this method is preferable to more commonly used methods. We discuss the kinematic structure and abundance patterns of small molecules including the sulfur-bearing species CS, SO, CCS, H_2_CS, and HCS+; oxygen-bearing molecules OH, SiO, and H_2_CO; and simple hydrocarbon molecules c-C_3_H_2_, l-C_3_H, and l-C_3_H^+^. Finally, we discuss the implications of the observed chemistry for the structure of the gas and dust in the ISM. Highlighted results include the following. First, whereas gas in the disk has a molecular hydrogen fraction of 0.65, clouds on the outer edge of the Galactic Bar and in or near the Galactic Center have molecular fractions of 0.85 and >0.9, respectively. Second, we observe trends in isotope ratios with Galactocentric distance; while carbon and silicon show enhancement of the rare isotopes at low Galactocentric distances, sulfur exhibits no trend with Galactocentric distance. We also determine that the ratio of c-C_3_H_2_/c-H^13^CCCH provides a good estimate of the ^12^C/^13^C ratio, whereas H_2_CO/H_2_(^13^C)O exhibits fractionation. Third, we report the presence of l-C_3_H^+^ in diffuse clouds for the first time. Finally, we suggest that CS has an enhanced abundance within higher density clumps of material in the disk, and therefore may be diagnostic of cloud conditions. If this holds, the diffuse clouds in the Galactic disk contain multiple embedded hyperdensities in a clumpy structure, and the density profile is not a simple function of A_V_.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/633/A120
- Title:
- SgrB2(M) ^13^CCC and C^13^CC spectra
- Short Name:
- J/A+A/633/A120
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Carbon molecules and their ^13^C-isotopologues can be used to determine the ^12^C/^13^C abundance ratios in stellar and interstellar objects. C3 is a pure carbon chain molecule found in star forming regions and in stellar shells of carbon-rich late-type stars. Latest laboratory data of ^13^C-isotopologues of C3 allow a selective search for the mono-substituted species ^13^CCC and C^13^CC based on accurate ro-vibrational frequencies. Our aim was to provide the first detection of the ^13^C-isotopologues ^13CCC and C^13^CC in space and to derive the ^12^C/ ^13^C ratio of interstellar gas in the massive star-forming region SgrB2(M) near the Galactic Center. We used the heterodyne receivers GREAT and upGREAT on board SOFIA to search for the ro-vibrational transitions Q(2) and Q(4) of ^13^CCC and C^13^CC at 1.9THz along the line of sight towards SgrB2(M). In addition, to determine the local excitation temperature we analyzed data from nine ro-vibrational transitions of the main isotopologue CCC in the frequency range between 1.6-1.9THz which were taken from the Herschel Science Data Archive. We report the first detection of the isotopologues ^13^CCC and C^13^CC. For both species the ro-vibrational absorption lines Q(2) and Q(4) have been identified, primarily arising from the warm gas physically associated with the strong continuum source SgrB2(M). From the available CCC ro-vibrational transitions we derived a gas excitation temperature of Tex=44.4^+4.7^_-3.9_K and a total column density of N(CCC)=3.88^+0.39^_-0.35_x10^15^cm^-2.. Assuming the excitation temperatures of C^13^CC and ^13^CCC to be the same as for CCC, we obtained column densities of the ^13^C-isotopologues of N(C^13^CC)=2.1^+0.9^_-0.6^_x10^14^cm^-2^ and N(^13^CCC)=2.4^+1.2^_-0.8_x10^14^cm^-2^. The derived ^12^C/^13^C abundance ratio in the C3 molecules is 20.5+/-4.2, which is in agreement with the elemental ratio of 20, typically observed in SgrB2(M). However, we find the N(^13^CCC)/N(C^13^CC) ratio to be 1.2+/-0.1, which is shifted from the statistically expected value of 2. We propose that the discrepant abundance ratio arises due to the the lower zero-point energy of C^13^CC which makes position- exchange reaction converting C^13^CC to C^13^CC energetically favorable.
- ID:
- ivo://CDS.VizieR/J/A+A/559/A47
- Title:
- Sgr B2(N) and Sgr B2(M) IRAM 30m line survey
- Short Name:
- J/A+A/559/A47
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The discovery of amino acids in meteorites fallen to Earth and the detection of glycine, the simplest of them, in samples returned from a comet to Earth strongly suggest that the chemistry of the interstellar medium is capable of producing such complex organic molecules and that they may be widespread in our Galaxy. Our goal is to investigate the degree of chemical complexity that can be reached in the interstellar medium, in particular in dense star-forming regions. We performed an unbiased, spectral line survey toward Sgr B2(N) and (M), two regions where high-mass stars are formed, with the IRAM 30m telescope in the 3mm atmospheric transmission window. Partial surveys at 2 and 1.3mm were performed in parallel. The spectra were analyzed with a simple radiative transfer model that assumes local thermodynamic equilibrium but takes optical depth effects into account.
2294. Sgr B2 spectral survey
- ID:
- ivo://CDS.VizieR/J/ApJS/117/427
- Title:
- Sgr B2 spectral survey
- Short Name:
- J/ApJS/117/427
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have surveyed the frequency band 218.30-263.55GHz toward the core positions N and M and the quiescent cloud position NW in the Sgr B2 molecular cloud using the Swedish-ESO Submillimetre Telescope. In total 1730, 660, and 110 lines were detected in N, M, and NW, respectively, and 42 different molecular species were identified. The number of unidentified lines are 337, 51, and eight. Toward the N source, spectral line emission constitutes 22% of the total detected flux in the observed band, and complex organic molecules are the main contributors. Toward M, 14% of the broadband flux is caused by lines, and SO2 is here the dominant source of emission. NW is relatively poor in spectral lines and continuum. In this paper we present the spectra together with tables of suggested line identifications.
- ID:
- ivo://CDS.VizieR/J/A+A/641/A135
- Title:
- Sgr dSph CEMP-r/s star abundance analysis
- Short Name:
- J/A+A/641/A135
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on the discovery and chemical abundance analysis of the first CEMP-r/s star detected in the Sagittarius dwarf spheroidal galaxy (Sgr dSph) by means of UVES high-resolution spectra. The star, found in the outskirts of Sgr dSph, along the major axis of the main body, is a moderately metal-poor giant (Teff=4753K, logg=1.75, [Fe/H]=-1.55) with [C/Fe]=1.13, placing it in the so-called "high-carbon band", and strong s-process and r-process enrichment ([Ba/Fe]=1.4, [Eu/Fe]=1.01). Abundances of 29 elements from C to Dy were obtained. The chemical pattern appears to be best fitted by a scenario where an r-process pollution event pre-enriched the material out of which the star was born as secondary in a binary system whose primary evolved through the AGB phase, providing C- and s-process enrichment.
- ID:
- ivo://CDS.VizieR/J/A+A/605/A46
- Title:
- Sgr dSph nucleus stars chemical abundances
- Short Name:
- J/A+A/605/A46
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Iron, Magnesium, Calcium, and Titanium abundances for 235 stars in the central region of the Sagittarius dwarf spheroidal galaxy (within 9.0'~=70pc from the center) from medium-resolution Keck/DEIMOS spectra. All the considered stars belong to the massive globular cluster M 54 or to the central nucleus of the galaxy (Sgr,N). In particular we provide abundances for 109 stars with [Fe/H]>=-1.0, more than doubling the available sample of spectroscopic metallicity and {alpha}-elements abundance estimates for Sgr dSph stars in this metallicity regime. We find for the first time a metallicity gradient in the Sgr,N population, whose peak iron abundance goes from [Fe/H]=-0.38 for R<=2.5' to [Fe/H]=-0.57 for 5.0<R<=9.0 arcmin. On the other hand the trends of [Mg/Fe], [Ca/Fe], and [Ti/Fe] with [Fe/H] are the same over the entire region explored by our study. We reproduce the observed chemical patterns of the Sagittarius dwarf spheroidal as a whole with a chemical evolution model implying a high mass progenitor (M_DM_=6x10^10^M_{sun}_) and a significant event of mass-stripping occurred a few Gyr ago, presumably starting at the first peri-Galactic passage after infall.
- ID:
- ivo://CDS.VizieR/J/MNRAS/427/2647
- Title:
- Sgr dSph stars spectral classification
- Short Name:
- J/MNRAS/427/2647
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present spectra of 1142 colour-selected stars in the direction of the Sagittarius Dwarf Spheroidal (Sgr dSph) galaxy, of which 1058 were taken with VLT/FLAMES multi-object spectrograph and 84 were taken with the SAAO Radcliffe 1.9-m telescope grating spectrograph. Spectroscopic membership is confirmed (at >99 per cent confidence) for 592 stars on the basis of their radial velocity, and spectral types are given. Very slow rotation is marginally detected around the galaxy's major axis. We identify five S stars and 23 carbon stars, of which all but four carbon stars are newly determined and all but one (PQ Sgr) are likely Sgr dSph members. We examine the onset of carbon richness in this metal-poor galaxy in the context of stellar models. We compare the stellar death rate (one star per 1000-1700yr) with the known planetary nebula dynamical ages and find that the bulk population produce the observed (carbon-rich) planetary nebulae. We compute average lifetimes of S and carbon stars as 60-250 and 130-500kyr, compared to a total thermal-pulsing asymptotic giant branch lifetime of 530-1330kyr. We conclude by discussing the return of carbon-rich material to the interstellar medium.
- ID:
- ivo://CDS.VizieR/J/A+A/610/A61
- Title:
- SGR 1806-20 & SGR 1900+14 quasi-periodic oscill.
- Short Name:
- J/A+A/610/A61
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Quasi-periodic oscillations (QPOs) discovered in the decaying tails of giant flares of magnetars are believed to be torsional oscillations of neutron stars. These QPOs have a high potential to constrain properties of high-density matter. In search for quasi-periodic signals, we study the light curves of the giant flares of SGR 1806-20 and SGR 1900+14, with a non-parametric Bayesian signal inference method called D3PO. The D3PO algorithm models the raw photon counts as a continuous flux and takes the Poissonian shot noise as well as all instrument effects into account. It reconstructs the logarithmic flux and its power spectrum from the data. Using this fully noise-aware method, we do not confirm previously reported frequency lines at {nu}=17Hz because they fall into the noise-dominated regime. However, we find two new potential candidates for oscillations at 9.2Hz (SGR 1806-20) and 7.7Hz (SGR 1900+14). If these are real and the fundamental magneto-elastic oscillations of the magnetars, current theoretical models would favour relatively weak magnetic fields B~6x10^13^-3x10^14^G (SGR 1806-20) and a relatively low shear velocity inside the crust compared to previous findings.
2299. 9 Sgr spectra 1999-2011
- ID:
- ivo://CDS.VizieR/J/A+A/542/A95
- Title:
- 9 Sgr spectra 1999-2011
- Short Name:
- J/A+A/542/A95
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The O-type object 9 Sgr is a well-known synchrotron radio emitter. This feature is usually attributed to colliding-wind binary systems, but 9 Sgr was long considered a single star. We have conducted a long-term spectroscopic monitoring of this star to investigate its multiplicity and search for evidence for wind-wind interactions.
- ID:
- ivo://CDS.VizieR/J/ApJS/213/35
- Title:
- SHELS: complete galaxy redshift survey for R<=20.6
- Short Name:
- J/ApJS/213/35
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The SHELS (Smithsonian Hectospec Lensing Survey) is a complete redshift survey covering two well-separated fields (F1 and F2) of the Deep Lens Survey to a limiting R=20.6. Here we describe the redshift survey of the F2 field (RA_J2000_=09h19m32.4s and DE_J2000_=+30{deg}00'00"). The survey includes 16294 new redshifts measured with the Hectospec on the MMT. The resulting survey of the 4deg^2^ F2 field is 95% complete to R=20.6, currently the densest survey to this magnitude limit. The median survey redshift is z=0.3; the survey provides a view of structure in the range 0.1<~z<~0.6. An animation displays the large-scale structure in the survey region. We provide a redshift, spectral index D_n_4000, and stellar mass for each galaxy in the survey. We also provide a metallicity for each galaxy in the range 0.2<z<0.38. To demonstrate potential applications of the survey, we examine the behavior of the index D_n_4000 as a function of galaxy luminosity, stellar mass, and redshift. The known evolutionary and stellar mass dependent properties of the galaxy population are cleanly evident in the data. We also show that the mass-metallicity relation previously determined from these data is robust to the analysis approach.
