E. VALTAOJA, Metsähovi Radio Research Station, Espoo, Finland

Extragalactic Continuum Sources

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Veloclly (km/s)Figure 3: NGC 7252: CO (1-0) and H I profilestowards this newly-born elliptical galaxy.

merger between two equal-mass spiralgalaxies, as suggested by its very per­turbed appearance, with two tidal tails.

If the infrared luminosity L1R is re-rad i­ated by dust heated by the recent starformation, the ratio L1R/M(H2) is an indi­cator of star-formation efficiency. Theseinteracting and merging galaxies havethe highest known ratios: L1R/M(H2) ofthe order of 50 or greater, while it is ofthe order 1-3 in normal galaxies. Thereis also the possibility that a significantpart of L1R comes from dust heated byan active nucleus (in that case the emis­sion region is highly confined towardsthe centre), so that the ratio L1R/M(H2) isnot a good indicator of star-formationefficiency. However, high L1R/M(H2)

Introduction

As with most other high-frequencyradio telescopes, continuum workoccupies only a small fraction - current­Iy about 5 % - of SEST's total time. Theimportance of these observations in in­creasing our understanding of quasarsand other extragalactic sources is, how­ever, large.

The millimetre-to-IR observationsprobe the innermost parts of the radio­emitting regions of active galactic nu­clei: the radio cores, possibly the begin­nings of radio jets, become optically thinon mm-wavelengths, where also theoutbursts reach their maximum stages.As these regions remain below the re­solving power and above the standardfrequencies of VLBI, high frequency fluxmeasurements give us our only glimp­ses of the very cores, the still mysterious

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ratios are still found in galaxies withoutnuclear activity.

The life time of the star burst can beextrapolated from these efficiencies. Intime scales of a few 106 yrs, the mergerremnants should become devoid ofmolecular gas. This result supports thecurrently well-developed idea that themerging of two spirals will form an ellip­tical galaxy, devoid of cold gas. An idealobject to test this hypothesis is thesouthern merger remnant NGC 7252,one of the pet galaxies of FranQoisSchweizer (1982). This object is con­spicuous by its two tidal tails, that repre­sent the "smoking gun" evidence of themerging of two spiral galaxies (Fig. 2).Numerous loops, shells and ripples addto the evidence. The luminosity profile issurprisingly regular and follows the r1

/4

law, characteristic of ellipticals, until alarge distance. Yet this object was seento be very rich in molecular gas (Duprazet al. 1989): about 3 109 MG, within7 kpc. The observed line shape sug­gests that the CO emission comes frommatter confined to a disk, which is alsoobserved in Ha. This surprising resultindicates that not all of the moleculargas is consumed in the star burst, aspreviously thought, or that matter con­tinues to fall down onto the disk, longafter the merging event.

At higher redshifts, the galaxies thatcan be detected in CO are all monsters:huge starburst galaxies, correspondingto interacting or merging objects, thefrequency of mergers being probably

sites of energy generation and channel­ing in active galaxies. Long wavelengths("Iong" in the case of quasars meaningeverything longer than one centimetre)show only evolved structures, such asold, ejected knots; the millimetre regimeis where the real action iso

Most events seen at centimetrewavelengths have their precursors onhigher frequencies. This forewarningcapacity is especially useful for spaceVLBI purposes in choosing the best"targets of opportunity" for observa­tions. The millimetre spectrum and itsvariations can also tell if compact struc­ture is present in the source, andwhether it will be a good candidate forVLBI observations; with sufficient fluxdata it may even be possible to producemodel maps of the sources. Clues to thenature of different radio sources mustalso be searched at high frequencies.

higher in the past. The ultraluminousIRAS objects have luminosities largerthan 10'2 .. Mirabel et al. (1988) havedetected four of these monsters,possessing 1-6 1010 MG of moleculargas. Their L1R/M(H2) ratio is between 20and 80, much larger than in classic star­burst galaxies, like Messier 82. Thehighest systemic velocity among theseobjects is 27,500 km/s, wh ich demon­strates tl1e ability of the SEST 15-mtelescope to detect faint and broademission lines.

This brief survey, far from exhaustive,already shows how exciting extragalac­tic work can be with the SEST 15-mtelescopel

ReferencesCombes, F., Gerin, M. (1985) Astron. Astro­

phys. 150,327.Combes, F., Gerin, M., Buta, R. (1989) As­

tron., Astrophys., in prep.Dupraz, C., Casoli, F., Combes, F. (1989) in

prep.Gerin, M., Nakai, N., Combes, F., (1988) As­

tron. Astrophys. 203, 44.Lynds, R., Toomre, A. (1976) Astrophys. J.

209,382.Mlrabel, I. F., Booth, R. S., Garay, G., Johans­

son, L. E. B., Sanders, D. B. (1988) Astron.Astrophys. 206, L20.

Sandqvist, Aa., Elfhag, T., Jörsäter, S., Lind­blad, P. O. (1989) in prep.

Schwartz, M. P. (1984) Monthly Notices Roy.Astron. Soc. 209, 93.

Schweizer, F. (1982) Astrophys. J. 252, 455.Theys, J.C., Spiegel, E.A. (1976) As/rophys.

J. 208, 650.

While SEST opens up completely newsouthern vistas, its location also pre­sents some problems in continuumwork. The continuum observer dreamsof uninterrupted multifrequency light­curves revealing the various con­stituents and processes found in ActiveGalaxy Nuclei (AGN), but the reality usu­ally shrinks to a scatter of isolated fluxmeasurements. In most cases, onewould greatly benefit from supportingdata on other frequencies, but there arenot many Southern telescopes availablefor that purpose.

SEST Measurements

During its first year SEST has beenused for most of the purposes outlined

Visiting Astronomers(October 1, 1989 - April 1, 1990)

above, with the continuum work dividedroughly equally between Swedish andFinnish groups. Most of the data havebeen obtained at 90 GHz, although thegroups have been striving to get alsomore 230 GHz observations.

The obvious starting point has beento get acquainted with the new part ofthe sky. Several surveys of the southernskies are now in progress. N. Whybornis observing a complete sampie ofbright, f1at-spectrum radio sources be­low declination - 25°, and a similar sur­vey between 0° and -25° is in pro­gress by E. Valtaoja. These surveys arefirst steps in gathering basic knowledgeof Southern hemisphere sources: theirhigh frequency spectra, variability, de­gree of compactness, etc., data whichcan be used both for statistical studiesand for selecting exciting individualobjects as targets for future investi­gations.

Selected subsets of sources havealso been observed: southern BL Lacsand highly polarized quasars (H. Teräs­ranta), radio quiet quasars (A. Kus), andSOurces observed in TDRS satellitespace VLBI experiments (R. Booth). Asthe Sources typically are observed attwo or more epochs for variability es-

Observing time has now been allocated forPeriod 44 (October 1, 1989 - April 1, 1990).The demand for telescope time was againmuch greater than the time actually available.

The following list gives the names of theVisiting astronomers, by telescope and inChronological order. The complete list, withdates, equipment and programme titles, isavailable from ESO-Garching.

3.6-m Telescope

OCI. 1989: Marano/Cappi/Held, Bender elal., Kudritzki/Husfeld/Gehren/Grolh/Butler/Baade/ROSaiHumphreys/Hummer, Ögelman/Gouiffes/MelnickiHasinger/Pietsch/Peder­sen, Danziger/BouchetlGouiffes/LucylWam­pler/Fransson, Nissen/Schuster, Fleming,GUZZolTarenghi, lovino/Shaver/Cristiani/Clowes/Pierre, de Lapparent et al.

Nov. 1989: de Lapparent et al., Guzzo/Collins/Nichol, Danziger/BouchetlGouiffes/LucylWampler/Fransson, Gry/Jourdain deMUizon/Lagrange - HenriNidal- Madjar/Fer­let, Wampler, Molaro/Castelli/Bonifacio, deBoer et al., Schwope/Beuermann, Breysa­cher/Azzopardi/LequeuxiMeyssonnierlWe­sterlund, de Boer et al., Marano/Mignoli/Zitel­IilZamorani.

Dec. 1989: Barbieri/Clowes/Cristiani/IOvino/La FrancaNio, Melnick/Gopal- Krish­naiSteppe/van Drom, Ögelman/Gouiffes/

timates, most of the work is still in pro­gress.

The Finnish group has used SEST toextend their long-time monitoring pro­gramme to higher frequencies. About 12of the most active and well-knownequatorial blazers have been observedroughly semimonthly in Chile. Althoughthe "high" (i.e., Northern) declinations ofsome of these sources have causedsome grumbling in the programme com­mittee, the SEST data fill a crucial gapbetween lower frequencies (Metsähovi,Itapetinga, Crimea) and IR observations(Hawaii) in what remains the most ex­tensive international effort to under­stand the radio behaviour of AGN. Mul­tifrequency monitoring has made possi­ble the separation of outbursts from theunderlying other components, showingthat shocked jet models give at least afirst approximation of what is going on invariable radio sources. Much remains tobe done, however: even the best ob­served quasar, 3C 273, continues tobehave in a highly erratic and surprisingmanner.

Harri Teräsranta from the MetsähoviRadio Research Station summarizes theexperience of the first year as folIows:"90 GHz flux measurements are now

Melnick, Hasinger/Pietsch/Pedersen, Dan­ziger/BouchetlGouiffes/LucylWampler/Fransson, Ardeberg/Lindgren/Lundström, deBoer et al., Danziger/BoucheVGouiffes/Lucy/Wampler/Fransson, Madejsky/RabolliNegalBassino, Hamann/SchmutzIWessolowski,Tadhunter/Fosbury/Morganti/Danziger/DiSerego Alighieri.

Jan. 1990: LortetITestor/Schild, Ögelman/Gouiffes/MelnickiHasinger/Pietsch/Peder­sen, Danziger/BoucheVGouiffes/LucylWam-pler/Fransson, Perrier/Mariotti/Mayor/Du-quennoy, Renzini/D'Odorico/Greggio/Bragaglia, MelnickiGopal-KrishnaiSteppe/Van Drom, Surdej et al., ChiosilBertelli/Bres­san, Nasi/OrtolaniNallenari/Gratton/Meylan,Heske/Jourdain de Muizon.

Feb. 1990: Jourdain de Muizon/D'Hen­decourt, Danziger/BoucheVGouiffes/Lucy/Wampler/Fransson, Ögelman/Gouiffes/Mel­nickiHasinger/Pietsch/Pedersen, D'Odorico,Danziger/BoucheVGouiffes/LucylWampler/Fransson, Wehrse/Hessman, Bergeron/Petit­jean/D'Odorico, Sparks/Macchetto/Ögerle,Norgaard-Nielsen/Joergensen/Hansen.

March 1990: BoulesleixiCapaccioli/Corradi/Le Coarer, Duval/Boulesteix/MonneVCorado, Ögelman/Gouiffes/Melnick,Hasinger/Pielsch/Pedersen, Danziger/BoucheVGouiffes/LucylWampler/Fransson,Reipurth/Dubath/Mayor, Capellaro/Held,Bender et al., Balkowski/Kraan-Korteweg/Maurogordalo, Mazure et al.

relatively routine work. The actual rmslevels achieved with 30 min integrationtimes have been from 40 to 80 mJy.230 GHz observations require goodweather, and it would be better to havethe observing run spread over a longertime span with several shorter sessionsto maximize the chances of success.The observing times should be nearly1 hour for one source if rms values of0.2 Jy are to be expected."

Future Programmes

The future will probably see a shiftfrom general surveys to dedicatedmonitoring of selected sources, hope­fully with increasing co-operation fromother Southern telescopes to get themost out of the observations. With newreceivers and increased experience,submillimetre observations will come tothe forefront: one of the challenges is tofollow the entire early evolution of a syn­chrotron flare in order to develop sec­ond-generation models for the growthof shocks in relativistic jets.

Still another field where SEST's im­pact will certainly be feit in the future ismillimetre VLBI, both on the ground andin space.

3.5-m NTT

Jan. 1990: Danziger/BoucheVGouiffes/LucylWampler/Fransson, Schneider/Giraud/Wambsganss, Bignami/Caraveo/MereghettilMignami, Mellier/Fort/Soucail.

Feb. 1990: Miley el al., Surdej et al.March 1990: Barthel/DjorgovskilTytler,

Danziger/BouchetlGouiffes/LucylWampler/Fransson, Tsvetanov/FosburylTadhunter,Bergeron et al., Bender el al.

2.2-m Telescope

Gcl. 1989: MPI TIME, Van der KruiVDeJong RS, HunVMandolesilWade, Ferraro/Brocato/Fusi Pecci/Buonanno, Piotto/Breso­lin/Capaccioli/Ortolani, Bertola el al.

Nov: 1989: Bertola et al., Collins/Guzzo/Nichol, Danziger/BouchetlGouiffes/Lucy/Wampler/Fransson, test new array (Moor­wood), des Boer el al., Barbieri et al., de Boerel al., AppenzelierlWagnerlWeigeltlBarth/Weghorn/Grieger, Surdej et al.

Dec. 1989: WeigeltlBarth/GriegerlWeg­horn, de Boer el al., Paresce/PanagiaiGil­mozzi, RafanellilCapaccioli/Marziani/SchulzH. Tadhunter/Fosbury/Morganti/Danziger/DiSerego Alighieri, Reiputh/Olberg/ Cameron/Boolh, Rafanelli/Capaccioli/Marziani/Schulz H.

Jan. 1990: Busarello/Longo/Feoli, Danzi­ger/BoucheVGouiffes/LucylWampler/Frans­son, MPI TIME.

Feb. 1990: Van der Veen/Blommaert/Hab­ing, Danziger/BoucheVGouiffes/LucylWam­pler/Fransson, Schwarz/Moneti, Pottasch/Manchado/Garcia Lario/Sahu, NotaiClam­pin/Paresce/Ferrari, Falomo/MaraschilTanzi/

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