ReferencesBinney, J., and Petrou, M. (1985). Mon. Not.

R.Asifon. SOG. 214,449.Faber, S. M., Baliek, B., Gallagher, J. S., and

Knapp, G. R. (1977). Astrophys. J. 214,383.

Jarvis, B.J. (1986). Astron. J. 91,65.Jarvis, B.J., and Freeman, K.C. (1985). As­

uophys. J. 295, 314.Kormendy, J., and Illingworth, G. (1982), As­

trophys. J. 256, 460 (KI).May, A., van Albada, T.S., and Norman, C.A.

(1985). Mon. Not. R. Astron. SOG. 214, 131.

Figure 6.

strongest supporting evidence for this isthe discovery of a faint luminous stellardisko

2. IC 3370 is highly cylindrically rotat­ing to much greater z distances thanhave previously been observed in box­or peanut-shaped bulges.

3. The kinematic data show thatIC 3370 has as much rotation as anoblate isotropic model flattened by rota­tion alone.

4. There is an unusually large amountof isophotal twisting in the bulge ofIC 3370 amounting to a total shift ofabout 25°. Merger or tidal processesmay offer the only satisfactory explana­tion for its occurrence.

5. The bulge of IC 3370 is very lumi­nous with MB = - 22.1, making it one ofthe most luminous bulges known.

100

-

50

I

Ne 4594 Major Ä.-'Xis

T •.'f--r-"'..... ..

T- ••.....- .~ ~ ..

• :/' -l' ••

I

I

I

in view of the large amount of isophotaltwisting observed. Slightly triaxial or ob­late elliptical galaxies with an approxi­mately axisymmetric potential cannotbe excluded however. Thus it seemsthat the most likely merger possibility forJC 3370 proposed by Binney and Petrouis the slow collision of two massive diskgalaxies which have appropriately in­c1ined total angular momentum vectors.The absence of a significant amount ofdust in IC 3370 would tend to argue infavour that the merging progenitorswere SO galaxies unless the merger pro­cess triggered efficient star formationdepleting nearly all of the gas. Theseproposals have no sound physical basisat present and can only be tested byadequate n-body experiments.

v. Conclusions

The main conclusions reached in thisstudy of IC 3370 are as folIows:

1. IC 3370 is an SOpec galaxy and notan elliptical as previously classified. The

oR dius ( I"CS cs)

I-50-100

• T• ..: iiI •• ' -". 'Jf

200 r-. _.: _. . ..: ... ".j ..

"'. '"....rr# .~ .~

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Ul

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Figure 5.

dissipative history as is generally be­lieved for the bright ellipticals? Thesmall colour gradient in IC 3370 arguesagainst a strongly dissipational col­lapse. This is also supported by the lackof a significant amount of highly dissi­pated material in the form of a diskoThese and other more subtle points re­quire us to look for a non-dissipativetype model for IC 3370.

One alternative possibility may lie withmergers as these have been shown tobe capable of producing the charac­teristic box and peanut shapes (Binneyand Petrou, 1985). Their models showedthat the slow accretion of a satellitegalaxy by a more massive host can leadto the box or peanut shapes with theproviso that the mass of the bulge mustnot amount to more than a small fractionof the overall mass of the host system.However, for IC 3370, the ratio of thebulge mass to total mass is almost unity.Also, the satellite capture hypothesiscannot work weil in the case of the hostsystem being highly triaxial, a possibility

Upgrading of the ESO 1.52-rn Telescope0. ALLOIN*, Observatoire de Paris, France, and 0. HOFSTADT, ESO

A Few Words of History

At the time the ESO Convention wassigned, two telescopes 1 metre in sizewere foreseen, one dedicated to photo­metric observations, the other to spec­troscopic work. The latter however, wassoon turned into a 1.52-metre tele-

• Chairperson of the ESO Users Committee

scope, a modified twin-brother of a tele­scope then under construction at theHaute-Provence Observatory. A ratherlarge building was planned to house thecoude spectrograph and an aluminizingplant for up to 2 metre diameter mirrors,and was erected in 1968.

The 1.52-metre spectroscopic tele­scope was first offered to visiting as­tronomers for the period September 1sI

1969 to March 1st 1970. The instrumen­tation then available consisted of thecoude spectrograph and a Cassegrainspectrograph from Marseille Observa­tory, aimed at radial velocity measure­ments. Later, an echelle spectrographwas installed at the coude focus, work­ing with an electronographic deviceand providing a resolution down to0.015 nm. This spectrograph is present-

18

Iy being modified so as to receive a CCOdetector and be remotely controlled. ABoiler and Chivens spectrograph waspurchased for the Cassegrain focus. Itwas first equipped with an Image Tube,then with the Image Oissector Scanner(1978) and a reticon device, and sinceMarch 1987, works with a CCO detec­tor. A set of gratings allows to reachresolutions from 0.1 to 1.35 nm for anentrance slit of 3 arcsec.

The Need for an Upgrading

Firstly, an instrument twenty years oldhas necessarily suffered from ageing:some mechanical and optical parts inparticular must be replaced. Secondly,the technology for telescope buildingand the observing conditions havechanged rapidly: no doubt that a shorttour at the various telescopes on La Sillawould convince you of this fact. Andfinally, requirements of the astronomershave changed according to technologi­cal progress. Remember that a pointingaccuracy of about 2 arcmin was seen as.acceptable by the time the 1.52-metretelescope was planned, while now weare all looking for much better perfor­mances ...

As far as possible, all instruments onLa Silla should meet these requirementswhich aim at a better efficiency andreliability. Along this line of thinking, anupgrading of the 1.52-metre telescopeappeared to be necessary and was initi­ated recently. In a similar way the 1metre photometric telescope has bene­fited by a complete check-up and hasbeen modernized at the same time.

It should be realized that such a taskis not as easy as it looks at first sight:precisely because the technological as­pects have changed so much! Moder­nizing a telescope from the sixties canbe time consuming and expensive.However, many interesting results are tobe expected from small to medium sizetelescopes if these are efficient and weilequipped. Indeed, they can provide thelarge amounts of data which are re­quested to perform serious research onvariability projects or survey projects. Tobe competitive these telescopes needan accurate computer-controlled point­ing, a precise and automatic guidingand must be equipped with fast andhigh quality instrumentation.

What 00 the 1.52-m TelescopeUsers Think?

In order to estimate which support tothis upgrading could be expected fromthe users community, an inquiry wassent around last April to the 55 as­tronomers having observed at the 1.52­metre telescope during the period April

1, 1986 to April 1, 1987. This inquiryconsisted of a set of questions regard­ing (i) the telescope itself and the gener­al observing conditions, and (ii) morespecifically the Image Oissector Scan­ner because this detector recentlyshowed serious signs of degradation. Atotal of 43 astronomers replied to thisinquiry, i.e. 78 %: we thank them verymuch for their help. From their answersthe following conclusions could bedrawn:

Regarding point (i), 65 % of the obser­vers are not satisfied with the presentobserving conditions. The rating forsuggested improvements went as: 93 %are in favour of a computer-controlledpointing, 74 % would appreciate theaccess to an automatic guiding system,58 % also favour a computer-controlleddome motion and 58 % see the need forobserving from a side-room. Finally, animpressive proportion of observers,90 %, would accept a close-down of theinstrument during two months if thiscould speed up the upgrading - even ifthis close-down disturbs temporarilytheir scientific programmes.

As far as point (ii) is concerned, only asubset of the astronomers sampie an­swered this part of the inquiry, thosehaving used the detector on the Boilerand Chivens spectrograph (24 of them).The answers are strongly dependent onthe epoch at which the lOS was used,since its impressive failures started lastOecember 1986. Most lOS users fromOecember 1986 to March 1987 noticestability problems, an increase of thenoise, the appearance of spikes and aspectacular loss in sensitivity. To thesuggestion of replacing the dying lOS bya CCO detector, 83 % of the usersagree while 17 % raise arguments infavour of the lOS (real-time data display,small size files, homogeneity of data ...)although they have no serious objectionto the CCO.

This inquiry has shown, if necessary,that the astronomical communitystrongly supports the upgrading of the1.52-metre telescope and that a speed­ing up of the action would be welcome.

Which Improvements Have BeenImplemented Already?

On the side of the telescope, up tonow the modifications have been mainlyof mechanical nature and are related tothe modernization of the telescopedrive.

Additional improvements have beenachieved for the auxiliary functions: (i) anew mirror 3 support has been im­plemented which does allow for easyand weil aligned optical configurationchanges between Cassegrain andcloude focii, (ii) four motorized sliding

counter-weights are now along the deltatube (iii) one motorized offset counter­weight is for the hour angle axis, (iv) abalancing counter-weight ring has beeninstalled below the mirror cell (v) there isa new motorized rotator for the Casse­grain instrumentation and, (vi) telescopeblocking devices have been mounted inorder to ensure safer and faster instru­ment exchanges.

On the side of the instrumentation, anew CCO detector has been attached tothe Boiler and Chivens spectrograph.

Future Upgrading

The telescope will get new servo­motor drives at both axes. These willallow for accurate tracking and off-set­ting. A high resolution encoder with anabsolute position read-out feature willbe installed. Automatic telescope anddome presetting will be implemented.An automatic guiding system forCassegrain observing and possiblycoude as weil, will be available. It isintended to develop an autonomoussafety system for the telescope, in orderto prevent collision with the pillars andthe platform. The telescope and in­strumentati,on cabling will be renewedand a cabling twist system will be incor­porated. Finally, a new control room willbe installed at the floor below the tele­scope. Regarding the instrumentation,the optics of the Boiler and Chivensspectrograph will be improved in orderto overcome the geometrical aberra­tions. It is also planned to reactivate theechelec spectrograph with a CCO de­tector.

While you are reading these lines, partof this future upgrading has all ready be­come past upgrading ....

Thinking of the future of small ormedium size telescopes, one route istowards modernized efficient instru­ments with only a few high qualityequipments. One might direct the effort,at the 1.52-metre telescope, in havingthe echelle spectrograph equipped witha CCO at the coude focus, and theimproved Boiler and Chivens spectro­graph at the Cassegrain focus, also witha CCO detector. This would lead to abetter set-up of the instrumentation be­cause of less frequent change-over.This whole upgrading is intended toraise the 1.52-metre telescope to thesame quality standard as now found onthe site.

A large fraction of the TRS staff at LaSilla is presently involved in this task,particularly W. Eckert and his workshopcrew for the mechanical modifications,M. Maugis for the new encoder inter­faces, J. Alonso for the servo-drives andG. Andreoni for the telescope controlsoftware. La Silla, June 29 th 1987

19