- ID:
- ivo://CDS.VizieR/J/ApJ/792/L2
- Title:
- C/2012 F6 (Lemmon) and C/2012 S1 (ISON) maps
- Short Name:
- J/ApJ/792/L2
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Results are presented from the first cometary observations using the Atacama Large Millimeter/Submillimeter Array (ALMA), including measurements of the spatially resolved distributions of HCN, HNC, H_2_CO, and dust within the comae of two comets: C/2012 F6 (Lemmon) and C/2012 S1 (ISON), observed at heliocentric distances of 1.5 AU and 0.54 AU, respectively. These observations (with angular resolution ~0.5"), reveal an unprecedented level of detail in the distributions of these fundamental cometary molecules, and demonstrate the power of ALMA for quantitative measurements of the distributions of molecules and dust in the inner comae of typical bright comets. In both comets, HCN is found to originate from (or within a few hundred kilometers of) the nucleus, with a spatial distribution largely consistent with spherically symmetric, uniform outflow. By contrast, the HNC distributions are clumpy and asymmetrical, with peaks at cometocentric radii ~500-1000km, consistent with release of HNC in collimated outflow(s). Compared to HCN, the H_2_ CO distribution in comet Lemmon is very extended. The interferometric visibility amplitudes are consistent with coma production of H_2_CO and HNC from unidentified precursor material(s) in both comets. Adopting a Haser model, the H_2_CO parent scale length is found to be a few thousand kilometers in Lemmon and only a few hundred kilometers in ISON, consistent with the destruction of the precursor by photolysis or thermal degradation at a rate that scales in proportion to the solar radiation flux.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/784/L7
- Title:
- CH_3_CH_2_SH detection in Orion KL
- Short Name:
- J/ApJ/784/L7
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- New laboratory data of ethyl mercaptan, CH_3_CH_2_SH, in the millimeter- and submillimeter-wave domains (up to 880GHz) provided very precise values of the spectroscopic constants that allowed the detection of gauche-CH_3_CH_2_ SH toward Orion KL. This identification is supported by 77 unblended or slightly blended lines plus no missing transitions in the range 80-280GHz. A detection of methyl mercaptan, CH_3_SH, in the spectral survey of Orion KL is reported as well. Our column density results indicate that methyl mercaptan is {=~}5 times more abundant than ethyl mercaptan in the hot core of Orion KL.
- ID:
- ivo://CDS.VizieR/J/ApJ/812/L5
- Title:
- CH_3_NCO (methyl isocyanate) transition frequencies
- Short Name:
- J/ApJ/812/L5
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A new interstellar molecule, CH_3_NCO (methyl isocyanate), has been detected using the 12m telescope of the Arizona Radio Observatory (ARO). CH_3_NCO was identified in spectra covering 48GHz (68-116GHz) in the 3mm segment of a broadband survey of Sgr B2(N). Thirty very favorable rotational lines (K_a_=0 and K_a_=1 only; E_u_<60K) originating in five consecutive transitions (J=8->7, 9->8, 10->9, 11->10, and 12->11) in both the A and E internal rotation species are present in this frequency range. Emission was observed at all of the predicted frequencies, with 17 lines appearing as distinct, uncontaminated spectral features, clearly showing the classic a-type, asymmetric top pattern, with T_R_^*^~20-70mK. The CH_3_NCO spectra also appear to exhibit two velocity components near V_LSR_~62 and 73km/s, both with {Delta}V_1/2_~10km/s --typical of molecules such as CH_2_CHCN, HNCO, and HCOOCH_3_ in Sgr B2(N). The column density of CH_3_NCO in Sgr B2(N) was determined to be N_tot_~2.3x10^13^ and 1.5x10^13^/cm^2^ for the 62 and 73km/s components, corresponding to fractional abundances, relative to H_2_, of f~7.6x10^-12^ and 5.0x10^-12^, respectively. CH_3_NCO was recently detected in volatized material from comet 67P/Churyumov-Gerasimenko by Rosetta's Philae lander, with an abundance ~1.3% of water; in Sgr B2(N), CH_3_NCO is roughly ~0.04% of the H_2_O abundance.
- ID:
- ivo://CDS.VizieR/J/ApJ/851/L46
- Title:
- CH_3_OCH_2_OH ALMA detection in NGC 6334I
- Short Name:
- J/ApJ/851/L46
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the detection of interstellar methoxymethanol (CH_3_OCH_2_OH) in Atacama Large Millimeter/submillimeter Array (ALMA) Bands 6 and 7 toward the MM1 core in the high-mass star-forming region NGC 6334I at ~0.1-1" spatial resolution. A column density of 4(2)x10^18^cm^-2^ at T_ex_=200K is derived toward MM1, ~34 times less abundant than methanol (CH_3_OH), and significantly higher than predicted by astrochemical models. Probable formation and destruction pathways are discussed, primarily through the reaction of the CH_3_OH photodissociation products, the methoxy (CH_3_O) and hydroxymethyl (CH_2_OH) radicals. Finally, we comment on the implications of these mechanisms on gas-phase versus grain-surface routes operative in the region, and the possibility of electron-induced dissociation of CH3OH rather than photodissociation.
- ID:
- ivo://CDS.VizieR/J/A+A/640/A65
- Title:
- CLASH brightest cluster galaxies CO spectra
- Short Name:
- J/A+A/640/A65
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Brightest cluster galaxies (BCGs) are excellent laboratories to study galaxy evolution in dense Mpc-scale environments. We have observed in CO(1->0), CO(2->1), CO(3->2), or CO(4->3), with the IRAM-30m, 18 BCGs at z~0.2-0.9 that are drawn from the Cluster Lensing And Supernova survey with Hubble (CLASH) survey. Our sample includes RX1532, which is our primary target, being among the BCGs with the highest star formation rate (SFR>~100M_{sun}_/yr) in the CLASH sample. We unambiguously detected both CO(1->0) and CO(3->2) in RX1532, yielding a large reservoir of molecular gas, M_H2_=(8.7+/-1.1)10^10^M_{sun}_, and a high level of excitation r31=0.75+/-0.12. A morphological analysis of the Hubble Space Telescope I-band image of RX1532 reveals the presence of clumpy substructures both within and outside the half-light radius re=(11.6+/-0.3)kpc, similarly to those found independently both in ultraviolet and in H in previous work. We tentatively detected CO(1->0) or CO(2->1) in four other BCGs, with molecular gas reservoirs in the range M_H2_=2x10^10-11^M_{sun}_. For the remaining 13 BCGs we set robust upper limits of M_H2_/M*<~0.1, which are among the lowest molecular gas to stellar mass ratios found for distant ellipticals and BCGs. By comparison with distant cluster galaxies observed in CO our study shows that RX1532 (M_H2_/M*=0.40+/-0.05) belongs to the rare population of star forming and gas-rich BCGs in the distant universe. By using available X-ray based estimates of the central intra-cluster medium entropy, we show that the detection of large reservoirs of molecular gas M_H2_>~10^10^M_{sun}_ in distant BCGs is possible when the two conditions are met: i) high SFR and ii) low central entropy, which favors the condensation and the inflow of gas onto the BCGs themselves, similarly to what has been previously found for some local BCGs.
- ID:
- ivo://CDS.VizieR/J/ApJ/690/837
- Title:
- CN and CO observations toward AGB stars
- Short Name:
- J/ApJ/690/837
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A survey of the ^12^C/^13^C ratio toward circumstellar envelopes has been conducted at millimeter wavelengths using the facilities of the Arizona Radio Observatory (ARO). The ratios were obtained for a sample of 18 local C- and O-rich asymptotic giant branch and supergiant stars from observations of the ^12^C and ^13^C isotopologues of CO and CN, respectively. The J=1->0 transitions of both molecules were observed at {lambda}=3mm using the ARO 12m telescope, while the J=2->1 lines of the two species were measured using the ARO Sub-Millimeter Telescope (SMT) at {lambda}=1mm. The ^12^C/^13^C ratios were determined from the CO data by modeling both transitions simultaneously with a circumstellar radiative transfer code, which can account for the high opacities present in the emission from this species. In the case of CN, the hyperfine structure was used to evaluate opacity effects. Ratios obtained independently from CO and CN are in good agreement.
- ID:
- ivo://CDS.VizieR/J/A+A/600/A71
- Title:
- C17O and C18O spectra of nine AGB stars
- Short Name:
- J/A+A/600/A71
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We seek to investigate the ^17^O/^18^O ratio for a sample of AGB stars containing M-, S-, and C-type stars. These ratios are evaluated in relation to fundamental stellar evolution parameters: the stellar initial mass and pulsation period. Circumstellar ^13^C^16^O, ^12^C^17^O, and ^12^C^18^O line observations were obtained for a sample of nine stars with various singledish long-wavelength facilities. Line intensity ratios are shown to relate directly to the surface ^17^O/^18^O abundance ratio. Stellar evolution models predict the ^17^O/^18^O ratio to be a sensitive function of initial mass and to remain constant throughout the entire TP-AGB phase for stars initially less massive than 5 solar masses. This makes the measured ratio a probe of the initial stellar mass. Observed ^17^O/^18^O ratios are found to be well in the range predicted by stellar evolution models that do not consider convective overshooting. From this, accurate initial mass estimates are calculated for seven sources. For the remaining two sources, there are two mass solutions, although there is a larger probability that the low-mass solution is correct. Finally, we present hints at a possible separation between M/S- and C-type stars when comparing the ^17^O/^18^O ratio to the stellar pulsation period.
- ID:
- ivo://CDS.VizieR/J/A+A/623/A154
- Title:
- CO datacube abd spectra of UGC 10214
- Short Name:
- J/A+A/623/A154
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Minor mergers play a crucial role in galaxy evolution. UGC 10214 (the Tadpole galaxy) is a prime example of this process in which a dwarf galaxy has interacted with a large spiral galaxy ~250 Myr ago and produced a perturbed disc and a giant tidal tail. We used a multi-wavelength dataset that partly consists of new observations (H{alpha}, HI, and CO) and partly of archival data to study the present and past star formation rate (SFR) and its relation to the gas and stellar mass at a spatial resolution down to 4 kpc. UGC 10214 is a high-mass (stellar mass M_*_=1.28x10^11^ M_{sun}_) galaxy with a low gas fraction (M_gas_/M_*_=0.24), a high molecular gas fraction (M_H2_/M_HI_=0.4), and a modest SFR (2-5 M_{sun}_/yr). The global SFR compared to its stellar mass places UGC 10214 on the galaxy main sequence (MS). The comparison of the molecular gas mass and current SFR gives a molecular gas depletion time of about ~2 Gyr (based on H{alpha}), comparable to those of normal spiral galaxies. Both from a comparison of the H{alpha} emission, tracing the current SFR, and far-ultraviolet (FUV) emission, tracing the recent SFR during the past tens of Myr, and also from spectral energy distribution fitting with CIGALE, we find that the SFR has increased by a factor of about 2-3 during the recent past. This increase is particularly noticeable in the centre of the galaxy where a pronounced peak of the H{alpha} emission is visible. A pixel-to-pixel comparison of the SFR, molecular gas mass, and stellar mass shows that the central region has had a depressed FUV-traced SFR compared to the molecular gas and the stellar mass, whereas the H{alpha}-traced SFR shows a normal level. The atomic and molecular gas distribution is asymmetric, but the position-velocity diagram along the major axis shows a pattern of regular rotation. We conclude that the minor merger has most likely caused variations in the SFR in the past that resulted in a moderate increase of the SFR, but it has not perturbed the gas significantly so that the molecular depletion time remains normal.
- ID:
- ivo://CDS.VizieR/J/ApJ/860/174
- Title:
- CO in Protostars (COPS): Herschel spectroscopy
- Short Name:
- J/ApJ/860/174
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present full spectral scans from 200 to 670{mu}m of 26 Class 0+I protostellar sources obtained with Herschel-SPIRE as part of the "COPS-SPIRE" Open Time program, complementary to the DIGIT and WISH Key Programs. Based on our nearly continuous, line-free spectra from 200 to 670{mu}m, the calculated bolometric luminosities (Lbol) increase by 50% on average, and the bolometric temperatures (Tbol) decrease by 10% on average, in comparison with the measurements without Herschel. Fifteen protostars have the same class using Tbol and Lbol/Lsmm. We identify rotational transitions of CO lines from J=4->3 to J=13->12, along with emission lines of ^13^CO, HCO^+^, H_2_O, and [CI]. The ratios of ^12^CO to ^13^CO indicate that ^12^CO emission remains optically thick for J_up_<13. We fit up to four components of temperature from the rotational diagram with flexible break points to separate the components. The distribution of rotational temperatures shows a primary population around 100K with a secondary population at ~350K. We quantify the correlations of each line pair found in our data set and find that the strength of the correlation of CO lines decreases as the difference between J levels between two CO lines increases. The multiple origins of CO emission previously revealed by velocity-resolved profiles are consistent with this smooth distribution if each physical component contributes to a wide range of CO lines with significant overlap in the CO ladder. We investigate the spatial extent of CO emission and find that the morphology is more centrally peaked and less bipolar at high-J lines. We find the CO emission observed with SPIRE related to outflows, which consists of two components, the entrained gas and shocked gas, as revealed by our rotational diagram analysis, as well as the studies with velocity-resolved CO emission.
- ID:
- ivo://CDS.VizieR/J/A+A/648/A49
- Title:
- Comet 46P/Wirtanen millimetre-wave spectra
- Short Name:
- J/A+A/648/A49
- Date:
- 08 Feb 2022
- Publisher:
- CDS
- Description:
- We present the results of a molecular survey of comet 46P/Wirtanen undertaken with the IRAM 30-m and NOEMA radio telescopes in December 2018. Observations at IRAM 30-m during the 12-18 Dec. period comprise a 2mm spectral survey, which covers 25GHz, and a 1mm survey which covers 62GHz. The gas outflow velocity and kinetic temperature have been accurately constrained by the observations. We derive abundances of 11 molecules, some being identified remotely for the first time in a Jupiter-family comet, including complex organic molecules such as formamide, ethylene glycol, acetaldehyde or ethanol. Sensitive upper limits on the abundances of 24 other molecules are obtained. The comet is found to be relatively rich in methanol (3.4% relative to water) but relatively depleted in CO, CS, HNC, HNCO or HCOOH.
