J/A+A/700/A194ivo://CDS.VizieR/J/A+A/700/A194doi:10.26093/cds/vizier/bc-nw/lbjeCDSHuertas-Roldan T.Alcolea J.Garcia-Hernandez D.A.Tafoya D.,Fonfria J.P.Diaz-Luis J.J.Manchado A.Bujarrabal V.Barzaga R.,Gomez-Munoz M.A.2026-08-03T06:56:22Z2025-08-19T08:51:24ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.frplanetary-nebulaemillimeter-astronomysubmillimeter-astronomyradio-astronomyThe circumstellar environments of planetary nebulae (PNe) are wonderful chemically rich astrophysical laboratories in which the ionization of atoms and the formation of simple and complex molecules can be studied. The new generation of high-sensitivity receivers opens the possibility to carry out deep observations which are needed to unveil weak atomic and molecular spectra lying in the millimeter (mm) range. The main goal of this work is to study the emission lines detected in the spectra of the bright C-rich PNe IC 418 and NGC 7027 and to identify all those emission features associated with radio recombination lines (RRLs) of light elements. We aim to analyze the RRLs detected on each source, and to model the sources and derive their physical parameters. This work allows us to provide the most complete and updated catalog of RRLs in space. We present the results of our very deep line survey of IC 418 and NGC 7027 carried out at 2, 3 and 7mm with the IRAM 30m and the Yebes 40m radio telescopes. We compare these observational data sets with synthetic models produced with the radiation transfer code Co3RaL. Results. Our observations towards the target PNe reveal the presence of several H and He i RRLs at mm wavelengths in the spectra of IC 418 and NGC 7027 and also of He ii RRLs in the spectrum of NGC 7027. Many of these lines had remained undetected until now due to their weakness and the lack of high-sensitivity observations at these frequencies. The data also confirm the absence of molecular emission towards IC 418, above a detection level of ~3mK [Tmb]. Conclusions. These mm observations represent the most extended RRL line survey of two C-rich PNe carried out so far, with most of the lines never reported before. These extremely complete catalogs evidence the importance of high-sensitivity observations and are expected to be very helpful in the line identification process in mm observations, in particular for still unknown or poorly characterized molecular species existing in the vicinity of ionized environments.2025A&A...700A.194Hhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/700/A194CatalogResearchIsServedByTAP VizieR generic servicehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/700/A194https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/700/A194http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/700/A194https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/700/A194https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/700/A194http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/700/A194GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapMillimeterRadiodefaultJ/A+A/700/A194/tableb1Physical parameters of the radio recombination lines (RRLs) detected in the planetary nebulae IC 418 and NGC 7027 at 2, 3, and 7mmrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintLineName of the RRL transitionmeta.id;phys.atmol.transProb;phys.atmol.transitioncharnutheoFrequency at the center of the lineMHzem.freqdoubleA1IC 418 Einstein coefficients**-1phys.atmol.transProbfloatStatus1IC 418 Status of the line (1)meta.codecharv01? IC 418 Central velocity of the linekm/sem.wl.central;spect.linefloatnullablee_v01? IC 418 Central velocity of the line errorkm/sstat.errorfloatnullablel_Tmb1Limit flag on Tmb1meta.code.errorcharTmb1? IC 418 Main beam temperature of the peakmKphys.temperature;meta.main;stat.maxfloatnullablee_Tmb1? IC 418 Main beam temperature of the peakmKstat.errorfloatnullablel_Area1Limit flag on Area1meta.code.errorcharArea1? IC 418 Area under the lineK.km/sphys.area;spect.linefloatnullablee_Area1? IC 418 Area under the lineK.km/sstat.errorfloatnullableFWHM1? IC 418 Full width at half maximum (2)km/sspect.line.widthfloatnullableComm1IC 418 Comments (3)meta.notechare_FWHM1? IC 418 Full width at half maximum (2)km/sstat.errorfloatnullableStatus2NGC 7027 Status of the line (1)meta.codecharv02? NGC 7027 Central velocity of the linekm/sem.wl.central;spect.linefloatnullablee_v02? NGC 7027 Central velocity of the linekm/sstat.errorfloatnullablel_Tmb2Limit flag on Tmb2meta.code.errorcharTmb2? NGC 7027 Main beam temperature of the peakmKphot.antennaTempfloatnullablee_Tmb2? NGC 7027 Main beam temperature of the peakmKstat.errorfloatnullablel_Area2Limit flag on Area2meta.code.errorcharArea2? NGC 7027 Area under the lineK.km**-1.s**-1phys.area;spect.linefloatnullablee_Area2? NGC 7027 Area under the lineK.km**-1.s**-1stat.errorfloatnullableFWHM2? NGC 7027 Full width at half maximum (2)km/sspect.line.width;em.opt.Rfloatnullablee_FWHM2? NGC 7027 Full width at half maximum (2)km/sstat.errorfloatnullableComm2NGC 7027 Comments (3)meta.notechar