SCORPIO at the 6-m telescope: current state and perspectivies for spectroscopy of galactic and extragalactic objects
aa r X i v : . [ a s t r o - ph . I M ] J un Baltic Astronomy, vol. ??, ??–??, 2011
SCORPIO AT THE 6-M TELESCOPE: CURRENT STATE ANDPERSPECTIVES FOR SPECTROSCOPY OF GALACTIC ANDEXTRAGALACTIC OBJECTS
V.L. Afanasiev and A.V Moiseev
Special Astrophysical Observatory of RAS, Nizhnij Arkhyz, Russia 369167;[email protected], [email protected]
Received: 2011 June 10; accepted: 2011 ??
Abstract.
A significant part of observations by Russian 6-m telescope iscarried out using SCORPIO multi-mode focal reducer. A lot of scientific datahave been collected using observations in direct imaging, slit spectroscopy andFabry-P´erot interferometry modes during the past ten years. Some results ofthese observations are considered in this review. We are also present a shortdescription of a new generation instrument named SCORPIO-2.
Key words:
Instrumentation: spectrograph – Instrumentation: polarimeters– ISM: kinematics and dynamics – Galaxies: active1. INTRODUCTIONIn the middle of the last century Georg Court´es (1960) suggested and realizedthe idea of a focal reducer. In addition to increasing the field-of-view of a largeoptical telescope and correction of the off-axis primary mirror aberration, a focalreducer makes it possible to have a multi-mode instrument, because it becomespossible to install dispersing elements in a output pupil between the collimator andthe camera, which turns the direct imaging system into an universal spectrograph.The first prototype of the device designed for spectroscopy and photometry of faintextended objects was an EFOSC camera at the 3.6-m ESO telescope (Buzzoni etal. 1984). Now a lot of multimode low-resolution spectrographs are used at middle-size and large telescopes. SCORPIO (Spectra Camera with Optical Reducer forPhotometric and Interferometric Observations) have worked at the primary focusof the 6-m SAO RAS telescopes since Sep. 2000. In the paper by Afanasiev &Moiseev (2005) we gave a short description o the device, while technical detailsare considered in Afanasiev et al. (2005). See also current information presented onthe SCORPIO web-page (see the footnote below). Today it is the most frequentlyused facility, that has been employed half of observation time at the 6-m telescope(Figure 1). In this review we consider briefly some scientific results obtained withthe use of SCORPIO and also our current work to modify and improve of atechnique of a faint object spectroscopy by the SAO RAS telescope.
V. Afanasiev, A. Moiseev
Fig. 1.
The percentage of the calendar time distributed by 6-m telescope ProgramCommittee for SCORPIO observations (left). Distribution of publications based onSCORPIO observations in 2001-2011 between different topics (right): the total amount(black) and in peer-review journals only (gray).
2. SCORPIO OBSERVING MODESThe multimode focal reducer allows various spectroscopic and photometricobservations to be performed within 6 arcmin field-of-view (see, Figure 2). Thelist of observing modes is as follows. • Direct imaging in broad-band
U BV R C I C filters; medium- and narrow-bandinterferometric filters. • Long-slit spectroscopy with volume phase holographic gratings (VPHGs). • Slitless spectroscopy for observations of spectrophotometric standard stars. • Multi-slit unit for spectroscopy with 16 movable slits ( ′′ in each height). • Spectropolarimetry using the analyzer based on a Savar plate (see Afanasiev& Moiseev (2005) for details of the data analysis). •
3D spectroscopy with a scanning Fabry-P´erot interferometer (FPI). Therealization of this technique in SCORPIO as well as a data reduction aredescribed in Moiseev et al. (2002) and in Moiseev & Egorov (2008)We can change the modes during the same night of observation, however somerestrictions exist, for instance, it is impossible to switch between long-slit andmulti-slit modes. The quick switch between the main modes (long-slit/imaging,FPI/imaging, etc.) allows an observer to choose targets that match best the currentatmospheric conditions (i.e. seeing and transparency). That is very important incase of unstable weather around the 6-m telescope site.3. SCIENTIFIC RESULTSAccording to the ADS database for the 2001 to June 2011 period, the dataobtained with SCORPIO were presented in 215 publications, including peer-reviewarticles, conference proceedings, telegrams, etc . They have been cited more than The updated list of publications is available at the SCORPIO web-page:
CORPIO at the 6-m telescope It would be quite impossible in a short paper togive a full review of all published results. Therefore, below we will consider onlycertain works selected according to our preferences in order to show a large rangeof tasks and methods.3.1. Solar System
The activity of a number of distant comets was investigated using the photometricand spectroscopic observations with SCORPIO – see, for instance, Korsun et al.(2008, 2010). The origin of the activity at the distance larger than 5 AU is apuzzle, however, molecular emissions were found in some objects. For example,in C/2002 VQ94 (LINEAR) emission bands of CO + and N +2 were detected at arecord heliocentric distance – 7.3 AU. It is an evidence of the fact that they hadbeen formed in the outer regions of the Solar System or in a pre-solar interstellarcloud in a low temperature ( T < K) environment.An interesting result was obtained by Afanasiev et al. (2007) who recorded thespectrum of a faint meteor during the observations of the spectra of galaxies withthe multi-slit unit. The velocity of the entry of the meteor body into the Earth’satmosphere estimated from the emission lines line-of-sight velocity is about 300km/s. Based on this results authors supposed that this meteor particle is likely tobe of an extragalactic origin.
Thanks to high optics transparence and the large diameter of the telescopemirror, SCORPIO is widely used for snapshot and monitoring observations offaint transient objects in the frameworks of several programmes with aims to studyspectral evolution of Novae (see for instance, Fabrika et al. 2009) and Supernovaestars, including distant core-collapse SNe probably associated with gamma-raybursts (Moskivitin et al. 2010). SCORPIO data provide a spectral confirmationfor newly discovered massive evolved stars (WR, LBV) in our Galaxy (Gvaramadzeet al. 2009) and other nearby galaxies: M33 (Valeev et al. 2009) and DDO68. Inthe latter case Pustilnik et al. (2008) have discovered a luminous blue variablefrom the transient event in the spectra of HII region of DDO68.Observations with a scanning FPI makes it possible to study the structure ofdesired spectral lines (H α , [O III], [SII]) simultaneously in a large (6 arcmin) field-of-view. It provides rich opportunities for investigating the emission-line kinematicsof the ionized gas in interplay between stars and the surrounding medium. Theexamples in our Galaxy are the study of jets and emission knots ejected fromyoung stellar objects (Movsessian et al. 2007, 2009), kinematics of bow shockfronts in pulsar-wind nebula CTB 80 (Lozinskaya et al. 2005), and supersonicmotions optical filament in the radio nebula W50 around the microquasar SS433(Abolmasov et al. 2010). The related object – a nebular complex associated withthe ultraluminous X-ray sources in the dwarf galaxy HoIX was also studied withthe SCORPIO/FPI (Abolmasov & Moiseev 2008). Based on the SCORPIO long-slit and FPI data Lozinskaya & Moiseev (2007) have presented evidences thatan explosion of a very massive star (Hypernova) seems to be a more plausiblemechanism of formation of the synchrotron superbubble in IC10 galaxy compared V. Afanasiev, A. Moiseev
Fig. 2.
Examples of data frames for different SCORPIO modes with the earlier proposed model of multiple supernova explosions. This workis a part of a series of papers aimed at investigating the kinematics of shellsand bubbles around star formation regions in nearby dwarf galaxies. A goodillustration is the IC1613 galaxy where Lozinskaya et al. (2003) have estimated theexpansion velocities of multiple gaseous shells using spatial-resolved kinematic datafor ionized (H α , SCORPIO/FPI) and neutral (21 cm, VLA) interstellar medium. Figure 1 shows that most of SCORPIO publications are related to nearbygalaxies. The H α images for a significant part of all galaxies in the Local Volume(within 10 Mpc) were obtained during a general imaging survey with SCORPIO.Measured H α fluxes were used to derive the total star formation rate density inthe Local Universe – . ± . M ⊙ yr − M pc − (Karachentsev & Kaisin 2010).The SCORPIO long-slit spectra were used to study the stellar population in twodE/dSph members of the nearby M81 group of galaxies (Makarova et al. 2010), CORPIO at the 6-m telescope whereas Chilingarian et al. (2009) used the multi-slit unit for the following-upspectroscopy of new discovered compact elliptical galaxies in order to investigatetheir origin and stellar population properties.Above we already discussed the ionized gas properties in the nearby dwarfgalaxies. Using the SCORPIO/FPI observations Mart´ınez-Delgado et al. (2007)have mapped the regions of supersonic gas motions in more distant blue compactgalaxies. They offered kinematic diagnostic diagrams that provide a possibility toinfer from FPI data the magnitude of the star formation activity in galaxies evenif they are not spatially resolved. The spectrophotometric observations conductedwith the use of SCORPIO allow one to estimate the oxygen abundance in HIIregions of extremely metal-deficient galaxies (see Pustilnik et al. (2010) and referencetherein). A detailed analysis of ionized gas morphology and kinematics in ninesuch galaxies shows the important role of recent interactions and mergers in thetriggering of their star formation (Moiseev et al. 2010).The ionized gas velocity fields derived from SCORPIO/FPI data cubes reveala complex kinematic picture in the disc of spiral galaxies caused by internal(seculiar evolution) and external (merging, gas accretion) effects: inflow steamingmotions in bars, polar discs and rings, circumnuclear counter-rotated component(see previous review in Moiseev 2007). FPI kinematic mapping is very helpful instudy of structure and dynamics of peculiar galaxies: colliding ring and polar ringgalaxies (see references in the review by Moiseev & Bizyaev 2009). Polar rings arean interesting example of peculiar systems that reveal outer rings or discs, rotatingin the plane approximately perpendicular to the disc of the main galaxy. The recentprogress in the study of polar rings with SCORPIO was presented in the paperby Brosch et al. (2010) who found the most distant kinematically confirmed polarring ( z = 0 . ). Here an early-type central galaxy is surrounded by a giant (with adiameter of over 48 kpc) ring of young stars and clouds of ionized gas, inclined ata steep angle to the stellar disc. In contrast to this large-scale structures, Moiseev(2010) has described the smallest ( r < kpc) polar gaseous discs in blue compactdwarf galaxies. The possible formation mechanism for these discs are merging oraccretion of external gas clouds with a specific direction of an orbital momentum.It was also suggested by Sil’chenko et al. (2011) who studied the stellar populationand kinematics properties in NGC7217 early-type spiral galaxy using SCORPIOlong-slit data. A minor merging event is also a most likely origin for the full-sizegaseous discs rotating in the opposite direction to the stellar ones in NGC2551and NGC5631 lenticular galaxies (Sil’chenko et al, 2009).The SCORPIO advantages in the spectroscopy of regions with a low surfacebrightness are illustrated in the papers by Zasov et al. (2008) about stellar kinematicsof the discs in S0-Sa galaxies and by Baes et al. (2007), where stellar populationage and metallicity distributions in the sample of elliptical galaxies were estimatedup to distances of 3 effective radii. The main important conclusion of this work isthe absence of a single power law for the metallicity gradient that is inconsistentwith the origin of the elliptical galaxies by a major merger. Together with data taken from some other instruments the SCORPIO spectrawere involved in long-term monitoring of H α and H β lines variations of the activegalactic nucleus of NGC4151 (Shapovalova et al. 2008) and 3C390.3 (Popovi´c etal. 2011). The main aim is a study of their ‘central engine’ including Broad Line V. Afanasiev, A. Moiseev
Region (BLR). The geometry of the BLR of 3C390.3 seems to be very complex, andinflows/outflows may be present, but the disc-like BLR is the dominant emitter.Recently, Afanasiev et al. (2011) presented the results of spectropolarimetricobservations for a sample of 15 active galactic nuclei. The magnetic field strengthsand radial distributions in an accretion disc around a supermassive black hole wereevaluated within the framework of traditional accretion disc models.The large-scale environment of active nuclei was also investigated in numerouspapers based on the data collected in the FPI mode. Smirnova et al. (2007)presented the analysis of global ionized gas kinematics in the disc of Mrk 533.In this galaxy the non-circular ionized gas motions at the distance of r < . kpc are associated with an outflow triggered by the nuclear radio jet intrusion inan ambient medium. A very complicated combination of the region with differentionization and kinematics properties was found in Mrk 344 (Smirnova & Moiseev2010). The most unusual feature is a large-scale cavern filled with a low-densityionized gas. This region seems to be the place where the remnants of a disruptedcompanion have recently penetrated through the gaseous disc of the main galaxy. SCORPIO shows a good advantage in the spectral identification of the extragalacticradio sources in a wide range of optical magnitudes up to m r = 23 − m . See,for example, the classifications, optical identifications and spectral redshifts forthe different samples of radio sources presented by Amirkhanyan et al. (2004) andAfanasiev et al. (2003). Some interesting objects were discovered. For instance,Amirkhanyan & Mikhailov (2006) found a very radio-loud QSO at z = 4 . .Recently Parijskij et al. (2010) presented the results of spectroscopy of 71 radiogalaxies and QSO with steep and ultra-steep spectra.SCORPIO follow-up spectroscopy makes a significant contribution to the systematicsearches for wide separation gravitational lens systems in the framework of CAmbridgeSloan Survey Of Wide ARcs in the skY (CASSOWARY). The most beautiful object(in our view) was the discovery of the Cosmic Horseshoe (CASSOWARY ′′ around a giant luminous redgalaxy at the z = 0 . (Belokurov et al. 2007). The source is a star-forming galaxythat has a z = − ) whichallows Quider et al. (2009) to study from VLT spectroscopy the metallicity andstarformation properties in the source galaxies with the quality that is currentlyunfeasible for unlensed galaxies at z ≈ − .4. NEW PERSPECTIVIESDuring its ten years of operation the SCORPIO has been repeatedly upgradedand improved. Unfortunately, opportunities for further upgrading have been exhausted.Also, a new optical scheme was necessary for spectral observations with largeformat CCD detector. Therefore SAO RAS began manufacturing a new multi-mode spectrograph with enhanced capabilities. The main novelty of the SCORPIO-2 versus its with previous version are as follows (see also Table 1): • The value of off-axis optical aberration are significantly (by half) decreased. • The device is specially designed to work under remote control from theInstitute building (under the mountain where the telescope is sited). The
CORPIO at the 6-m telescope Table 1.
Comparision of the 6-m telescope old and new facilities
SCORPIO SCOPIO-2Detector EEV 42-40, K × K E2V 42-90, K × . K Direct imaging:Max. filters positions 10 (in two wheels) 27 (in three wheels)Field-of-view 6.1 arcmin 6.1 arcminLong-slit spectroscopy set of slits with fixed width ( . − ′′ ) ; variable slit width ( − ′′ ) ;single VPHG position wheel with 9 grating holdersFPI Common carriage with grating holder independent holderMulti-slit unit 16 slits in × arcmin field-of-view 16 slits in × arcmin field-of-viewIntegral-field unit – × lenslet, . ′′ / lensPolarymetry Savar plates, rotated in twopositions Single and double Wollaston prisms;apochromatic phase plates λ/ , λ/ ;rotated analyser number of exchangable elements installed simultaneously in the device issignificantly increased. • The opportunities for polarimetry (spectra and images) are greatly expanded. • The new multi-mode focal reducer includes an Integral-field unit (IFU) basedon the combination of small lenses with optical fibers. This scheme wasoffered by Georg Court´es (1982) and it was first implemented in the twogenerations of the MultiPupil Fibers Spectrographs (MPFS) at the 6-mtelescope (Afanasiev et al. 1990, 2001). Now this type of IFUs is widelyused in middle- and large-size telescopes. The SCORPIO-2/IFU × ′′ field-of view is divided by square lenses array with a scale of . ′′ per lens.Behind each lens an optical fibre is located whose other end is packed intotwo pseudo-slits in the spectrograph entrance.The first test observations by the 6-m telescope were carried out in June, 2010.Some electronic and mechanical parts (integral-field and multi-slit units) are stillunder construction. We are confident that the commissioning of SCORPIO-2 willsignificantly enhance the abilities of the 6-m telescope in the study of differentobjects in our Galaxy as well as in extragalactic scales.ACKNOWLEDGMENTS. This work was supported by the Russian Foundationfor Basic Research (project no. 09-02-00870) and by the Russian Federal Program‘Kadry’ (contract no. 14.740.11.0800). We are grateful to Olga Smirnova for herhelp in the text preparation. AVM is also grateful to the Dynasty Fund and the8th SCLCA Organizing Committe for their financial support.REFERENCESAbolmasov P., Maryeva O., Burenkov A. N. 2010, AN, 331, 412Abolmasov P., Moiseev A. 2008, MexRevA&A, 44, 301Afanasiev V. L., Borisov N. V., Gnedin Yu. N. 2011, AstL, 37, 302Afanasiev V. L., Dodonov S. N., Sil’chenko O. K., Vlasyuk V. V. 1990, PreprintSpec. Astrophys. Obs., N54Afanasiev V. L., Dodonov S. N., Moiseev A. V. 2001, in Stellar Dynamics: FromClassic to Modern , eds. L.P. Ossipkov & I.I. Nikiforov, Saint Petersburg, 103Afanasiev V. L., Dodonov S. N., Moiseev A. V. et al. 2003, ARep, 47, 458
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