------------------------------------------------------------------------ Querying NED (TAP) ------------------------------------------------------------------------ BACKGROUND. Here, I discuss querying the NASA Extragalactic Database (NED) maintained by IPAC. It is a useful starting point to understand "table access protocol" (TAP) defines a service protocol for accessing general table data, including astronomical catalogs as well as general database tables. Access is provided for both database and table metadata as well as for actual table data. The fundamental reference is https://www.ivoa.net/documents/TAP/20100327/REC-TAP-1.0.html The query language of TAP is "Astronomical Data Query Language" (ADQL), though some may support variants of SQL. TAP services support data queries, metadata queries (which allow a user to discover the names of tables and columns to be in data queries), and Virtual Observatory Support Interface (VOSI; informs users of the capabilities of VO serviced offered). TAP requests can be synchronous asynchronous. The main query parameters are QUERY, LANG, REQUEST, FORMAT (optional), PHASE (optional, async query only), EXECUTIONDURATION (optional), and MAXREC (optional). For small inquiries synchronous calls are sufficient: https://ned.ipac.caltech.edu/tap/sync?QUERY={QUERY}&LANG=ADQL&REQUEST=doQuery&FORMAT={FORMAT}&MAXREC={MAXREC} ------------------------------------------------------------------------ NED ------------------------------------------------------------------------ This is an excellent starting point for the vocabulary of NED https://ned.ipac.caltech.edu/help/ui/ned_help?popup=1 Reference: https://ned.ipac.caltech.edu/Documents/Guides/Interface/TAP I found the IPAC URL to be very helpful. ------------------------------------------------------------------------ NED: Cone-search ------------------------------------------------------------------------ For instance the call below is a cone-search of NED with RA, DEC and Radius, all in deciamal degrees. The ouput form is plain "TEXT". Other options include VOTABLE,FITS,JSON,CSV,TSV,TEXT,HTML. Note that "+" here stands for " ". URLencoding can be painful and ideally you should URLencode anything other than alphnumberic, "-","_",".". [Look up my Unix page for URL encoding for other details] curl -o out.txt "https://ned.ipac.caltech.edu/tap/sync? query=SELECT+*+FROM+objdir+WHERE+CONTAINS(POINT('J2000',ra,dec), CIRCLE('J2000',66.76957,26.10453,0.01))=1&LANG=ADQL&REQUEST=doQuery&FORMAT=text" $ head -1 out.dat | sed 's/ *//g' | tr '|' '\n' | nl -s " " 1 prefname 2 ra 3 dec 4 uncmaja 5 uncmina 6 uncposa 7 gallon 8 gallat 9 bhextin 10 refcode 11 pretype 12 z 13 zunc 14 zflag 15 zrefcode 16 n_crosref 17 n_notes 18 n_gphot 19 n_posd 20 n_zdf 21 n_ddf 22 n_assoc 23 n_dist 24 n_class 25 n_images 26 n_spectra 27 objid 28 pos_refid 29 z_refid See Appendix on how the meaning of the keywords. From the keyword list we select prefname(1), ra(2), dec(3), pretype(11), z(12), zunc (13) $ sed 2d out.dat | sed 's/ //g;s/ "/"/g;' | awk -F'|' '{print $1,$2,$3,$11,$12,$13}' ------------------------------------------------------------------------ Appendix: Key word schema ------------------------------------------------------------------------ Keywords are found in TAP Schema. The relevant table is "TAP_SCHEMA.columns" We need only the keywords associated with NED objects. Next, for readability, we rid of all the spaces that IPAC tables revel in $ curl -o out.txt "https://ned.ipac.caltech.edu/tap/sync?QUERY=SELECT+*+FROM+TAP_SCHEMA.columns&REQUEST=doQuery&LANG=ADQL&FORMAT=text" $ cat out.txt | grep "NEDTAP.objdir" | sed 's/ //g' | awk -F'|' '{print $3"\t"$4}' 1 "objid" "Internal identifier for the object in NED" 2 "prefname" "preferred object name" 3 "pretype" "NED preferred object type" 4 "ra" "RA in decimal degrees J2000.0" 5 "dec" "DEC in decimal degrees J2000.0" 6 "gallon" "Galactic Longitude in degrees of the object" 7 "gallat" "Galactic Latitude in degrees of the object" 8 "bhextin" "Foreground Galactic Extinction Burstein & Heiles" 9 "uncmaja" "Uncertainty Ellipse, Semimajor Axis in arcseconds" 10 "uncmina" "Uncertainty Ellipse, Semiminor Axis in arcseconds" 11 "uncposa" "Uncertainty Ellipse, PA in degrees (East of North)" 12 "refcode" "Reference Code for the object position" 13 "zflag" "Redshift flag" 14 "z" "Redshift in z." 15 "zunc" "Redshift Uncertainty" 16 "zrefcode" "NED-used refcode for redshift of this oobject" 17 "pos_refid" "Internal Refcode ID for position" 18 "z_refid" "Internal Refcode ID for redshift in this position" 19 "n_crosref" "Number of crosref data frames" 20 "n_notes" "Number of notes data frames" 21 "n_gphot" "Number of photometric data frames" 22 "n_posd" "Number of position data frames" 23 "n_zdf" "Number of redshift data frames" 24 "n_assoc" "Number of association data frames" 25 "n_ddf" "Number of diameter data frames" 26 "n_images" "Number of image data frames" 27 "n_spectra" "Number of spectra data frames" 28 "n_dist" "Number of distance data frames" 29 "n_class" "Number of classification data frames" ------------------------------------------------------------------------ Appendix: Galaxy types: NED ------------------------------------------------------------------------ * Star or Point Source ** Double star *Ass Stellar association *Cl Star cluster AbLS Absorption line system Blue* Blue star C* Carbon star EmLS Emission line source EmObj Emission object exG* Extragalactic star (not a member of an identified galaxy) Flare* Flare star G Galaxy GammaS Gamma ray source GClstr Cluster of galaxies GGroup Group of galaxies GPair Galaxy pair GTrpl Galaxy triple G_Lens Lensed image of a galaxy HII HII region IrS Infrared source MCld Molecular cloud Neb Nebula Nova Nova Other Other classification (e.g. comet; plate defect) PN Planetary nebula PofG Part of galaxy Psr Pulsar QGroup Group of QSOs QSO Quasi-stellar object Q_Lens Lensed image of a QSO RadioS Radio source Red* Red star RfN Reflection nebula SN Supernova SNR Supernova remnant UvES Ultraviolet excess source UvS Ultraviolet source V* Variable star VisS Visual source WD* White dwarf WR* Wolf-Rayet star XrayS X-ray source !* Galactic star !** Galactic double star !*Ass Galactic star association !*Cl Galactic Star cluster !Blue* Galactic blue star !C* Galactic carbon star !EmObj Galactic emission line object !Flar* Galactic flare star !HII Galactic HII region !MCld Galactic molecular cloud !Neb Galactic nebula !Nova Galactic nova !PN Galactic planetary nebula !Psr Galactic pulsar !RfN Galactic reflection nebula !Red* Galactic red star !SN Galactic supernova !SNR Galactic supernova remnant !V* Galactic variable star !WD* Galactic white dwarf !WR* Galactic Wolf-Rayet star