stars TWHyaandHD100546 stars TWHyaandHD100546 circumstellar disksaroundtheyoung circumstellar disksaroundtheyoung Millimetre obser Millimetre obser have thedustcontinuum andHCO observed sky. diskslocatedinthesouthern protoplanetary We of forhighresolution imaging new opportunity withreceivers theCompactArray forthe3-mmatmosphericwindow provides a of recentupgrade The thespectrum. of detail inthispart andthephysical degrees, and chemical conditionscanbeprobedin from afewtenstohundreds of temperaturesranging thesedisksbecausethediskmaterialbeyond afewstellarradiiisat of properties millimetre wavelengths at System. Observations for characterising areespeciallyimportant thephysical similartotheearlySolar Many young emissionfromcircumstellardustdiskswithproperties stars exhibit T. Wong (ATNF) D. Wilner, T. Bourke(CfA,USA);C.Wright (ADFA); J.Jörgensen, E.vanDishoeck(Leiden,TheNetherlands); stars TWHyaandHD100546 circumstellar disksaroundtheyoung Millimetre obser reports Astronomy component. thiscompactdisk evidencefor provide direct thefirst observations Array TheCompact system. thatacircumstellardiskcomponentmust bepresentinthe at1.2mmwhich observed suggests the flux HD100546usingonlyanextendedenvelope donotaccountfor thefar-infraredreproduce emission of distribution. Modelsthat energy from itsspectral well withexpectations TWHyaagrees from observed flux Figure 12shows the89GHzcontinuumThe emissiondetectedfromTWHyaandHD100546. thedustwithindisk. substantialprocessingof Hale-Bopp andindicative of incomet bands, silicate similartothoseobserved spectroscopy shows strongcrystalline remarkably AU),size, (8,000 about8arcseconds aswell Mid-infrared emissionfromdust. asstrongmillimetre substantial HD 100546isanearby HerbigBestarandshows adisk-like lightdistributionof scattered objects. i.e.,evolution growth, toward significantparticle planet-sized substantially evolved, withindicationsof wavelengths theTWHya diskis usingsingledishtelescopes. Modellingallavailable datasuggests molecularlinesat submillimetre astronomical units(AU). Itsdiskhasbeendetectedinanumber of approximately 200 at least3.5arcseconds, equivalent toalinearsizeof extends toaradiusof TW Hyaisisolatedfromanymolecularcloudbutretainsaface-ondiskvisibleinscatteredlightthat two about arcseconds. of three antennas, withanangularresolution usingtwowere compactantennaconfigurationsof observed comet-like dust.These silicates, shows indicative crystalline of spectrum Herbig Bestarwhose infrared disk targets, TWHya,theclosestknownyoung classical TTauri southern star, andHD100546,anearby stars TWHyaandHD100546 stars TWHyaandHD100546 circumstellar disksaroundtheyoung circumstellar disksaroundtheyoung Millimetre obser Millimetre obser vations of vations of vations of vations of vations of page 17 +

( J = 1–0)

line emission at 89GHz(3.4mm)fromtwoline emissionat

Astronomy reports = 1 – 0) J (

+ are depleted due to a + line for collisional excitation is excitation line for collisional = 1 – 0) J (

+ line. The models all have disk masses of The line. models all have 0.03 + page 18 spectrum of TW Hya, position. the continuum integrated over

= 1 – 0) J (

+ , the detection ofextended be present must emission indicates high densities -3 cm line emission from the line emission from Gaussian size with a fitted TW Hya disk is spatially resolved, 4 = 1 – 0) J (

Images obtained with the Compact Array showing radio continuum emission at 89 GHz from the showing radio continuum emission at 89 GHz from Array Images obtained with the Compact + Figure 12 young stars TW Hya and HD 100546. to large radii, independent of model for the disk. and chemical HCO No any detailed physical solar masses and disk radii of 200 AU. High depletion High solar masses and disk radii of has been observed disks of in other young 200 AU. varying size and indicates that substantial depletion occurs throughout the disk, as expected for planet formation through accretion. combination ofcombination in the warm photodissociation and freezing-out surface in the cold parts layers of the disk accretion based either on a radiatively-heated These models, disk shielded from stellar activity. disk structure,structure two-layer consistent with the Compact Array are for or a passive observations, ofboth the size scale and the absolute intensity the HCO emission was detected toward HD 100546, HD a surprising detected toward result.emission was Observations of more abundant the 110 – 115 GHz rangespecies CO in the needed. are modelling ofPrevious the TW Hya disk suggestsHCO CO and like that species Figure 13 shows the HCO the shows Figure 13 approximately 6 x 10 approximately of of Since the critical density 3.2 arcseconds. the HCO The velocity and line-width of and The velocity the narrow emission line are in agreement with single dish observations. The HCO

Astronomy reports kilometres persecond. Figure 13 Imaging HCNemissionaroundRScl Imaging HCNemissionaroundRScl has been observed inseveral othersources.has beenobserved HCNinthedetached shellismostlikely due toitsphotodissociationintoCN, as lack of emission. The theCO which thattheHCNenvelopeHCN spectra, indicate isexpandingmoreslowly thanthebulkof by higher-transition, single-dish iscorroborated ingeometry difference theCOdata. The from inferred attached envelope detachedshell recentmasslossratherthantheolder(andhencelarger) resultingfrom withinthecalibrationuncertainties. Thus,flux withan itappearsthattheHCNemissionisassociated isconsistentwiththeSEST flux totalCompact resolvesArray The thesource (Figure14). partially only aboutonearcsecond,sothateven ourhigh-resolutionimaging maximum (FWHM)of full widthathalf between June andOctober2002.We withaGaussian thattheHCNemissionisextremely compact, found threeantennas, 31–413m, withbaselinesranging from R Sclinseveral compactconfigurationsof Array’s theHCN ledustoobserve restrictedfrequencyrange were madeinaCOemissionlinewiththeSwedish-ESO SubmillimetreTelescope (SEST),theCompact RScl ashellaround of thathadindicatedthepresence Although theprevioussingle-dishobservations (compared, forinstance, tomolecularclouds). smallangularsize relatively 3-mmsystembecausethey of are thecurrent for simplestructures theshell).Notwithstanding theirscientificinterest,circumstellarshellsalsomake ideal“testsources” of thewind(relatedtosymmetry isotropy of of variation (related totheshellthickness)anddegree themass-loss theshell,butalsotimescaleof not onlytheexpansionvelocity of one candetermine molecularemissionintheshellathighangularresolution, heliumshellburning. Byobserving onset of massloss, perhaps duetothesudden increaseintherateof at somepointinthepasttherewas asudden athindetached shellindicatesthat losing massinaslow stellarwindisquitetypical,butthepresenceof anddust.For moleculargas adyingstartobe which is believed tobeencircledby adetached shellof 3-mmsystemwas theCompactArray thecarbon-richredgiantstarRSculptoris, for targets thefirst One of M. Lindqvist,H.Olofsson(Stockholm Observatory, Sweden) T. Wong (ATNF); F. L.Schoeier(LeidenObseratory, TheNetherlands&Stockholm Observatory, Sweden); Imaging HCNemissionaroundRScl Imaging HCNemissionaroundRScl Imaging HCNemissionaroundRScl HCO + spectrum ofTWHyashowingthedetectionanarrowspectrum emissionlinecentred atavelocityof3 Velocity (kilometrespersecond) page 19 (J = 1–0 ) lineat88.6GHz.We observed

Astronomy reports ) and envelope size, using the HCN size, ) and envelope 2 page 20 Channel maps of HCN (J =1 – 0) emission from R Scl. The beam size is 2.7 x 1.8 arcseconds. The velocity R Scl. The beam size is 2.7 x 1.8 arcseconds. Channel maps of HCN (J =1 – 0) emission from data (both single-dish and interferometer) as constraints. The best-fit envelope size is about 1,000 AU, about 1,000 size is The envelope best-fit and interferometer) (both single-dish data as constraints. modelling the Compact Arraywhereas data of alone yields a size (comparable to the size of only 300 AU in our high-resolution maps).the emission region Thus a single set of model parameters cannot high optical depth the of single-dish and interferometer fit both the simultaneously Possibly data. the to changes conditions of in the physical the emission very sensitive HCN lines makes envelope the inner that as clumping in the mass distribution) are(such not accounted for in our model. A detailed radiative transfer code, based on the Monte Carlo method, has been used to jointly model the been used to jointly method, has on the Monte Carlo based transfer code, radiative A detailed Array Compact data. The and single-dish HCN are the current inputs to the model main mass-loss rate have we year) and the stellar radiation(in solar masses per for these, With reasonable assumptions field. to H for (relative the HCN abundance values calculated the best-fit Figure 14 per second. have been binned to 2 kilometres of rest) to the local standard channels (given relative

Astronomy reports wings wings Planetar Planetar characteristic isknown. More unusual emissionpeaks. withfour isthe“DD”source withthis Onlyoneothersource aswell areexpectedtobestarswithbipolarshells. asslopinginneredges.with slopingouteredges These thestarthanonother. “Dw”starshave The OH1612-MHzspectra is much ononesideof stronger have oneemissionpeak which much isvery thantheother—thisshows stronger thatthemaseremission the shell.Inoursamplewe seeseveral variations ontheclassicdouble-peaked “De” spectra The profiles: an expandingsphericalshell,withthetwo onthefrontand rear of peaksbeingemittedfromsmall“caps” between thetwo andslopinginneredges outer edges peaks.steep ischaracteristic spectralprofile This of the85sources, (“D-type”)at1612MHz,with double-peaked 57exhibit aclassic spectrum profiles. Of thespectral We have ontheshapeof categories, classifiedthespectrausingsixdifferent depending 1612MHz. OHmaserspectra,forsourcesinoursample, atafrequency of Figure 15shows examplesof symmetrical ordistorted. onthewindspeeds,provide andonwhetherthewindsarelikely accurateinformation tobespherically lasers.molecules isproducedby maserspectraalso amasereffect—themicrowave The equivalent of conditionsinalayer onthephysical aroundthecentralstar. fromthese gas radiation formation The stellarwinds.outflowing Each moleculerequiresdifferentphysical andprovides conditionstoexist in- radioemissionfrom hydroxyl, waterobserving andsiliconmonoxide moleculesthatarelocatedinthe OHmasersourcesintheGalacticplane(Sevenster etal.). For thissample, we are previous studyof To 85post-AGB starsfrom a investigate this question, we have selectedawell-defined sampleof nebulae. seeninsomeplanetary andothercomplicatedstructures geometries causes thebutterfly-wing stellarevolution. Bystudying thepost-AGB what starswe maybeable todetermine post-AGB phaseof windsbeginsearly nebulae inthe non-sphericalplanetary stars anditseemslikely thatthe shapingof phase known astheAGB. nebulae arealsoseeninpost-AGB seen inplanetary different geometries The known (post-AGB) aspost-asymptoticgiantbranch starsandhave evolved beyond the secondgiant nebulae. stars are These toplanetary starsthatare theimmediateprecursors We are studyingasampleof may beimportant. thecentralstars may effects, causegravitational of orrotation insomedirectionsonly. thestellarwindstoflow stars constrain Alternatively, companionstarsorplanets fieldsfromthe isthatseveral explanation magnetic theoriesarebeingdebated. Onepossible different known, are notyet but geometries of causesforthisproliferation The structures. complex, filamentary wings, butterfly orshow ellipticalorbipolarshapes, insomecaseswith circular, othershave theshapes of nebulae canbespectacularlybeautifulandreveal forms.While someappear manydifferent Planetary nebulae. as planetary stars andtheswept-up shellsmay thenbeseenasglowing areknown ionisednebulae. Starsinthisstage mass inhot,low-density, the fastwinds. hot windssweep uptheremainingmaterialsurrounding The have gas beenblown away, fromouter layers losingmassinslow of densewindstolosing change stars the astar’sAfter mostof originalmassback intotheinterstellarmedium. of transfer morethanhalf theirmassthroughslow, densestellarwinds. fractionof isthat Such moststarsshedalarge stages winds interestinthe“giant” particular insizeandbecomehotter.expand whilethestellarcoresdecrease Of outer layersgreatly changes. The structural throughasequenceof hydrogen, theygo core-burning of low-to-middlemassstars. Whenstars, out like ourown Sun, run nebulaearetheremnantsof Planetary R. Deacon(UniversityofSydney);J.Chapman(ATNF); A. Green (UniversityofSydney) wings Planetar wings wings Planetar Planetar y nebulaeandbutter y nebulaeandbutter y nebulaeandbutter y nebulaeandbutter y nebulaeandbutter page 21 fly fly fly fly fly

Astronomy reports page 22 Some examples of OH 1612 MHz spectra of post-AGB stars, obtained from data taken with the Parkes data taken with Some examples of OH 1612 MHz spectra of post-AGB stars, obtained from In our sample we also find five “S-type” sources. These only show a single peak of “S-type” sources. find five also we In our sample emission, maser but the “I” or irregular Finally stars. and post-AGB with AGB in common characteristics have otherwise stars with such emission peaks and a larger range. multiple Post-AGB than usual velocity spectra have geometries. irregular envelope with exotic associated spectra are usually of with still-to-come measurements together our maser data, From the stellar magnetic fields and imagesdetailed radio of have to some stars evolve to clarify why we hope the outflowing winds, and others do not. asymmetric winds Figure 15 top right-hand corner with a radio telescope in September 2002. The catalog name of each star is given in the types type given below the name. The 85 stars in this study have been classified into six different category DD-types), single (S-type) or irregular double (D, De, Dw and are depending on whether the OH maser profiles (I-type).

Astronomy reports Image reference: (Stockholm University, Sweden);NASA(USA) Photo credit: B.Balick(UniversityofWashington, USA);V. Icke(LeidenUniversity, TheNetherlands);G. Mellema super-sonic velocitiesofmore than300kilometres persecond. Hubble SpaceTelescope, showsapairofhigh-speed“jets”gasmovingawayfrom thecentre ofthenebulaat Figure 16 M2-9 isastrikingexampleof“butterfly”orbipolarplanetarynebula.Thisimage,takenwiththe Image STScI-PRC1997-38 page 23

Astronomy reports ray captures a captures ray a captures ray ray captures a captures ray ray captures a captures ray a captures ray page 24 nova nova nova nova nova ” super ” super ” super ” super ” super On the evening of 10 December 2001, the Rev. Robert Evans was conducting his regular supernova conducting of was Evans Robert On the evening the Rev. 2001, 10 December of from his backyardpatrol Mountains west in the Blue when he came across in the an interloper Sydney, late-type spiral galaxy majority of In an era when the vast nearby NGC 7424. are discoveries supernova or as part of telescopes, robotic made by trained Evans’ programs, search supernova the high-redshift him to maintain a proud record of allowed and trusty photographic have telescope eye, 12-inch memory, of discovery the 241st supernova and his 39th discovery, 2001ig was Supernova discoveries. supernova 2001. Since its commissioning, the Compact has played a leading roleArray in the monitoring of several II Type from most notably SN 1987A and SN 1978K. Radio emission at wavelengths, radio supernovae years after the or even months, searched for) until weeks, is typically not detected (or even supernovae ofoutburst. On the evening made use of 15 December 2001, we Saturday six hours of unallocated time on the Compact Array to make images of SN 2001ig at frequencies of 8.6, 4.8, 2.5 and 1.4 GHz. Eve, Year’s On New detection at the highest frequencies. a positive surprise, to our Somewhat there was on three Compact Array system 12-mm receiver detected at 18.8 GHz using the prototype it was antennas. Figure 17 shows an image of the field at 4.8 GHz from Compact Array observations taken on 17 February 2002. SN 2001ig is the upper of as contours; bright sources shown the source to the the two the results from our Compact is an unrelated background Figure 18 shows Arraysouthwest source. The 4.8 GHz data are shown. only the 8.6 and radio “light curve”of monitoring program; clarity, for a into three phases—a rapid turn-on can be divided supernova with a steep spectral index, due in large part to a decrease in the line-of-sight absorption; a peak in the flux is first seen at the higher which density frequencies;SN 2001ig had begun to 2002, a more gradual By March phase. decline in an optically-thin fade at 5 and 8 GHz, but then abruptly before doubled in flux for three weeks, and remained that way it again from a briefly In late dramatic excursions August, resuming its decline. Such halted its decline. and generally ofsmooth decline are rare, thought to be associated with the interaction the blast ejecta with a dense and rather inhomegenous circumstellar medium. SN 2001ig is one of only a half of examples dozen or so known the in which IIb” supernova, a “Type suggesting ofmuch that lines seen in their early optical spectra soon fade away, their outer hydrogen could also account which for this, possible mechanisms Two shed before the star exploded. were layers for the bumps in the radio light curve, are thermal pulses due to carbon/helium flashes in the core of a progenitor occurring5 – 10 solar mass asymptotic giant branch star, on periodic time scales of around or a modulation of500 years, a red supergiant progenitor a wind due to eccentric orbital motion about binary clumping Efforts leading to a pinwheel-like in the circumstellar medium. companion, massive are to model the observed in the context underway behaviour ofnow while Compact Array these scenarios, monitoring of 2003. throughout SN 2001ig will continue S. Ryder (Anglo-Australian Observatory); (Anglo-Australian of Sydney); E. Sadler (University S. Ryder Subrahmanyan (ATNF); R. USA) Laboratory, Research (Naval K. Weiler “baby “baby The Compact Ar Compact The Ar Compact The “baby The Compact Ar Compact The “baby “baby The Compact Ar Compact The Ar Compact The

Astronomy reports frequencies of4.8 and8.6GHzoveraperiodofapproximately 400days. Figure 18 radio sources. Thelowerradiosource isanunrelated background source. ofthegalaxyNGC7424fromimage oftheoutskirts theDigitizedSkySurvey. SN2001igisupperleftofthetwo Figure 17 The radiolightcurveofSN2001ig, showingthechangeinintensityofradioemissionat Contours showingthe4.8-GHzradioemissionfrom theregion around SN2001ig,overlaidonan page 25

Astronomy reports A . X-ray ObservatoryX-ray some can, in arkes arkes arkes arkes arkes Chandra ), and a characteristic age of 2,900 years. -3 observation of in SNR G292.0+1.8, shown

to look for new detections of pulsarsyoung , Chandra page 26 source, with a fluxsource, density at 1,400 MHz of and a low 80 microJansky

as deeply as possible results encouraged new In a 10-hour integration using the efforts. at Parkes very weak Chandra Pulsar discoveries at P discoveries Pulsar at P discoveries Pulsar Figure 19. The X-ray data of TheFigure 19. X-ray is pulsar wind nebula within which arcminute a two this source reveal previously without a pulsar remnant had been searched While this supernova located a point source. detection, the radio luminosity. X-ray pulsations were with the help of detected subsequent to and X-ray radio luminosity. the radio discovery. central beam of detected PSR J1124–5916, with a pulse period of system,we the multibeam 135 a moderate dispersion measure (330 pc cm milliseconds, PSR J1124–5916 is a Pulsar discoveries at P discoveries Pulsar of USA); D. R. Lorimer (University University, USA); B. M. Gaensler (Harvard (Columbia University, Camilo F. (ATNF) UK); R. N. Manchester Manchester, 2002 yielded a remarkable vintage of a central telescope playing the Parkes with pulsar discoveries, young role. of pulsars are objects Young of interest for a variety The of physics reasons. core collapse in evolved and magnetic stars can be inferred from observations spin period, space velocity, the initial which provide offield distributions of while measurements stars, neutron and luminosities, their beaming properties, spectraare crucial for determining the Galactic population and birthrate of pulsars Young pulsars. and emit substantial amounts of exhibit period glitches, frequently X- and gamma can be rays—these observed to learn about the internal composition of and the pulse emission mechanisms. neutron stars, in compact non-thermal neutron stars are embedded In addition, young wind pulsar radio and/or X-ray wind, or otherwise interact with their pulsar medium confines the relativistic where the ambient nebulae The embedded pulsars are of remnants. unique probes host supernova and immediate their environment the local interstellar medium. pulsars young for is the Galactic plane and more specifically in supernova location to search A natural and supernova Galactic pulsars between associations establishing bona fide However, remnants. 1970 (those of by known were business: two remnants has been a painfully slow five the Crab and Vela), 2000, remnants and 1,400 pulsars are known. and only 1985, than 200 supernova although more 10 by by in this regard—a survey productive not been immensely of for associations have Searches 88 supernova pulsars! remnants in the 1990s netted zero associated pulsar survey multibeam of recently the Parkes More system using a 13-beam receiver the Galactic plane, at a frequency of a very large broadly covered comparable to that of with sensitivity 1,400 MHz, area the best previous surveys of This survey remnants. been extraordinarily has successful, supernova but a pulsar between to date has yielded only one new association 700 pulsars, approximately discovering a discussion of remnant (for and a supernova remnant in the supernova PSR J1119–6127, pulsar, this Report Annual 2000). G292.2–0.5 see the ATNF that the existence of pulsars that relies on the premise a method to detect young used have We a pulsar the presence of also indicate must wind nebula decided to We pulsar. an energetic young and reasonably search pulsar wind nebulae cases, unambiguously identify a pulsar wind nebula and its embedded pulsar even when pulsations are when pulsations unambiguously identify a pulsar wind nebula and its embedded pulsar even cases, not detected. the beautiful by example is provided One such complication with this approach is that it is not always clear whether a particular clear compact object is a always is that it is not complication with this approach images recent X-ray from the pulsar wind nebula. However, Pulsar discoveries at P discoveries Pulsar at P discoveries Pulsar

Astronomy reports of PSRJ1124–5916, obtainedfrom Parkesdata,isoverlaid. G292.0+1.8. Thepositionofthepulsarisindicatedbyarrow andthemeanpulseprofile Figure 19 tolearn. relatively pulsarobservers newlessonforradio interest,such asyoung pulsars, thisisa photonsfromastronomicalsourcesof obtaining ahandfulof have atall!WhileX-ray astronomers longbeenusedtospendingaday aday orso, if timesof integration using when withthebestpresent-day telescopesonly aredetectable radio with luminositiesthat themdoso Our studyhasshown manyyoung However, pulsarsbeamtowards that the Earth. of many young pulsars. luminosity distributionandbeamingfractionof relevant tothesesearches isunderway onthecombinationof andshouldyieldusefulconstraints thesensitivity andselectioneffects andX-raystudies at radio wavelengths, analysisof andacareful two years, andthesearches continue. newly discovered The objectsarebeinginvestigated infollow-up pulsars, associated withwindnebulae (insomecaseswithinsupernovae), have beendetectedinthepast Arecibo, Bank,Jodrell Green BankandParkes telescopes. young weak sixvery andenergetic Inall, Following thisdiscovery, pulsarwindnebulaewere aspossiblewiththe searched manymore asdeeply Chandra X-rayimageoftheoxygen-rich1,700yearoldcomposite SNR page 27

Image credit: NASA/Rutgers/J. Hughes et al.

Astronomy reports solar 12 -massive spiral -massive spiral -massive -massive spiral -massive -massive spiral -massive spiral -massive solar masses and a total dynamical mass of solar masses and a total dynamical mass 1.5x10 page 28 solar masses. Thedensity of solar masses. more massive galaxies much 9 10 y of a super y of a super y of y of a super y of y of a super y of a super y of galaxy galaxy Discover Discover than this characteristic value is poorly constrained, however, as these super-massive galaxies are very rare. as these super-massive constrained, is poorly however, value than this characteristic a super-massive discovered have we Through a large receiver, multibeam survey that utilised the Parkes spiral galaxy at a distance of suggest telescope Data from the Parkes 140 Megaparsecs. that the galaxy J0836–43 has an HI mass ofHIZOA 7x10 galaxy How massive can a spiral galaxy can Current become? massive predict that theoretical models How galaxies spiral the like form the merger from ofMilky Way 25% and between was smaller galaxies at times when the Universe 50% of its current age. This merger process is thought to create a population of spiral present-day M*. galaxies densities decline value, whose number a characteristic exponentially at masses higher than see page 32) support this theory and set M* to a neutral HIPASS, from Observational (e.g. evidence (HI) mass ofhydrogen 6x10 approximately J. Donley, B. Koribalski (ATNF); R. Kraan-Korteweg (University of Guanajuota, Mexico); A. Schroeder A. Kraan-Korteweg R. Mexico); (University of Guanajuota, (ATNF); B. Koribalski J. Donley, team ZOA and the (ATNF) UK); L. Staveley-Smith (University of Leicester, Discover masses. Thistimes that of HI mass is 20 masses. and the total mass is at least five Galaxy Milky our own Way spiral galaxies known, J0846–43 among the most massive mass! This places HIZOA times the Milky Way’s a handful ofwith only galaxies whose such Some masses are comparable. HI and/or total dynamical galaxies 1752, UGC 12591, and NGC 1961. include Malin I, ISOHDFS 27, UGC high-resolution observations with the Compact ArrayFollow-up confirmed J0836–43 is in that HIZOA fact a single system, with a disk radius of and an inclination-corrected kiloparsecs 66 rotational velocity of as a function of rotation curve, the rotational velocity 312 kilometres per second. The galaxy’s radius, largeis constant at radii. This suggests J0836–43 has a large dark normal that, like HIZOA spiral galaxies, a propertyby current also predicted disk radius, the beyond well halo extending hierarchical matter clustering models of galaxy formation.This that, galaxy if is so large and massive formed at the very ofbeginning us had time to complete 10 rotations! to giving In addition only have it would the Universe, insights into the HI properties of J0836–43, our observations at the HIZOA determined have we that these data, data. From radio continuum also provided ArrayCompact have formingJ0836–43 is probably stars at a rate of per year. about 26 solar masses in the near- (AAT) J0836–43 with the Anglo-Australian Telescope also observed have HIZOA We behind the plane of J0836–43 is located Because HIZOA in a infrared K and H bands. the Milky Way as the Zone ofregion known the optical B-band emission originating from the galaxy is Avoidance, by nearly 12 magnitudes ofobscured us from obtaining an optical image of dust extinction, preventing than that on the optical light. The less severe emission is much the effect on infrared Luckily, the galaxy. us to determine allowed observations therefore of both the inclination have AAT 65 degrees, the galaxy, of as the distribution as well its old stellar population. Both a galactic bulge and disk can be inferred from emission. Thethe infrared bulge of has a central surface brightness 15 magnitudes per square arcsecond and a scale length of The disk has a scale length of 2 kpc. out to a radius of 4 kpc and can be detected 20 through 1 magnitude of even kpc, K band. extinction in the infrared J0836–43 is one ofThe galaxy HIZOA Although a nearby galaxies spiral detected. ever the most massive The galaxies image, are there is no evidence that interacting. two the galaxy can be seen in the AAT and integrated field emission ofvelocity suggesting no disturbances, J0836–43 show it is a that HIZOA The detection ofnormal, galaxy. J0836–43 albeit very galaxy massive, such as HIZOA a super-massive fundamental questions that arise when formulatinghelps us to answer theories ofgalaxy evolution. galaxy galaxy Discover Discover

Astronomy reports seen asthebrightstripextending overvelocitiesfrom approximately 10,400to11,000 kilometres persecond. Figure 21 peak value,inincrements of10%. obtained from Compact Array data,overlaid.Thecontour levelsshowtheHIemissionfrom 10%to90% ofthe Figure 20 ways todetectsuch hiddengiants. withreceivers thebest blindsurveys Large-scale such astheParkes multibeam receiver provide oneof A “position–velocity”diagramforHIZOA J0836–43alongthemajoraxisofgalaxy. Thegalaxyis A K-bandimageofHIZOA J0836–43from theAnglo-AustralianTelescope withtheHIcontours, page 29

Astronomy reports vey vey vey vey vey The observing team present at Narrabri for the team present The observing left to right: Lister From September pilot survey. Kate Ron Ekers, Jennifer Donley, Staveley-Smith, Carole Smith, Mike Kesteven, Elaine Sadler, In the background, Wilson. Jackson, Warwick seen observing the antennas CA02 and CA03 are –70 meridian between declinations of –60 and degrees. time with the antennas which were not being used were time with the antennas which for fast scanning. radio imaging ofFollow-up detected the sources carriedin the survey was out in October 2002, more accurate positions and fluxgiving densities. Almost half within the 226 detected sources lay degrees offive and can be the Galactic plane, and supernovae identified with Galactic HII regions, planetary The nebulae. remainder are extragalactic made up ofsources, candidate quasars (60%), galaxiesradio (20%) and faint optical objects or blank fields (20%). The 18 GHz survey in 2003. will continue page 30 ray 18 GHz pilot sur ray 18 GHz pilot sur ray 18 ray 18 GHz pilot sur ray 18 ray 18 GHz pilot sur ray 18 GHz pilot sur ray 18 irst results from the Compact from results irst the Compact from results irst irst results from the Compact from results irst irst results from the Compact from results irst the Compact from results irst Ar Ar F F In Septemberfor 2002, as a pilot study an all-sky we radio imaging survey wavelengths, at millimetre observed square degrees 1,216 of the southern sky wideband (4 GHz a novel at 18 GHz using bandwidth) analogue correlator on one baseline of imaging surveys Several ofthe Compact Array. the already been carriedradio skyhave out at where the 0.3 and 5 GHz, between frequencies radio population powerful source is dominated by galaxies but at and fainter starburst galaxies, 5 GHz only small areas of above frequencies sky been studied in detail. This is mainly because have small fields of large radio telescopes typically have at high frequencies, arcminutes) view (one to two making it extremely to observe time consuming large areas of Measuring the high-frequency sky. properties of extragalactic radio sources is crucial for interpreting and high- the high-sensitivity resolution maps of the cosmic microwave background that being produced are now by WMAP and is also importantsatellite missions like for studies of galaxies and their cosmic active evolution. The survey is made possible by using the new in combination Compact Array 12-mm receivers with a 4 GHz bandwidth prototype correlator (the standard at ATNF recently developed Compact Array correlator of a bandwidth has 128 MHz).The increased bandwidth means that the for short is high even sensitivity continuum large areas of allowing integration times, sky to be On 13 – 17 observed in a fast-scanning mode. scanned the region ofSeptember 2002, we sky declinationsbetween of –60 and –70 degrees antennas ofusing two the array as a two-element We interferometer with the wide-band correlator. 15 square roughly degrees per hour to a covered detection limit of The Compact 60 milliJansky. used in a “split array” so that Array mode, was regular synthesis imaging could be carried out at the same Ar Ekers, Mike team; Roberto Ricci (SISSA, Italy); Ron of Sydney) for the 20-GHz survey Elaine Sadler (University (ATNF/University Walker Mark (ATNF); Wilson Ravi Subrahmanyan, Warwick Kesteven, Lister Staveley-Smith, Italy) Observatory, (ANU); Gianfranco De Zotti (Padova Jackson of Sydney); Carole F Ar Ar F F

Astronomy reports from thegalaxy’s nucleusterminateanddumptheirenergy. concentrated atthehotspots(roughly onemillionlightyearsfrom theparent galaxy)where relativistic jetsofplasma in thePilotSurvey, overlaid onanopticalimagefrom theDigitizedSkySurvey. Thehigh-frequency radio emissionis frequency (843MHz)radioemission from theSUMSSsurvey. Thebluecontoursshowthe18 GHzemissionimaged radio galaxyshownhere (anellipticalgalaxyatz=0.0963) are relatively nearby. Here thered contoursshowlow- Figure 23 due tosources associatedwiththeLarge MagellanicCloud. Galactic disksources suchasHIIregions. Thesmaller excessatlatitudesof–30to–40degrees is degree binsinGalacticlatitude.Thepeaknearlatitudezero corresponds tothepopulationof Figure 22 While manyofthesources are detectedin thePilotSurvey associatedwith distantquasars,some,likethe A histogramshowingthe detected source densityfrom infive- the18GHzPilotSurvey page 31

Astronomy reports page 32 An unbiased census of hydrogen in hydrogen of census unbiased An in hydrogen of census unbiased An Universe the local Universe the local In 1997 an international of team set out to survey astronomers the entire southern sky for neutral receiver. multibeam radio telescope equipped with the 21-cm the Parkes (HI) emission using hydrogen This instrument is a very survey efficient the first us to conduct tool, allowing large-scale blind neutral intermediate both in the and out to distances neighbourhood of survey, hydrogen Galaxy, the MilkyWay All Sky Survey),of (HI Parkes as HIPASS known The 170 Megaparsecs. data taking for this survey, effort has gone and since then much finished in 2002, into analysing the largewas we Here, dataset. on some ofconcentrate the progress the extragalactic that has been made for component of HIPASS. data consists of and The eight degrees HIPASS eight by cover sky, on the which each 530 cubes, thirds these cubes comprise almost two from –1,200 to 12,700 kilometres per second. Together velocities of 388 has been directed to the most attention So far, –90 to +25 degrees. from declination the sky, southern cubes south of Our first task after creating the data cubes is to identify declination 2 degrees. extragalacticthis was found that line signals in the noisy background. HI 21-cm emission It was the results of independent automaticmost efficiently finder done using two scripts, which were merged. man-made detections at clouds and by to be polluted Galactic high-velocity frequencies known from the list of removed interference were The remaining 130,000 potential detections were detections. subjected to a series of this process, After three different individuals. by for verification checks manual times larger almost a twenty than any sample 4,300 HI selected galaxies, left with approximately were we existing HI selected sample. the skyFigure 24 shows distribution ofThe = 0 indicates dashed line at b the plane sources. the HIPASS of hinders which All optical redshift surveys extinction close to this line, from severe suffer the Galaxy. ofthe identification a large region of extragalactic sources over an incomplete and hence leads to sky, ofpicture the large-scale structure ofaffected by is not that HIPASS The figure clearly shows galaxies. extinction and measures the galaxy in all regions of distribution equally efficiently This illustrates the sky. ofthe power the large-scale to study structure in the local Universe. HIPASS of analysis A more quantitative the large-scale structure as the two-point is possible with a tool known correlation This probability of function. measures the excess distance finding another galaxy at a given this function has been studied extensively optically selected galaxies, For any galaxyfrom in the sample. morphological and star formation type, to be dependentand has been shown on galaxy luminosity, form a two-dimensional Figure 25 shows ofactivity. the correlation function of The galaxies. HIPASS correspondvertical and horizontal axes to separations galaxies between orthogonal and parallel to the finally leads to line of some mathematics, Integrating and applying lines, along vertical sight, respectively. ofa measurement comparison, the 26. the real space correlation is shown in Figure For function, which of (AAT), Telescope the at Anglo-Australian correlation function from the 2dF galaxy redshift survey, selected galaxies optically This diagram is also shown. that our sample of shows HI-selected galaxies, representing a population of clustered than the optically- is less strongly galaxies, evolving more slowly These here. gas-rich effects galaxies play are at two in might only survive Possibly, selected sample. could triggerwhich regions without too many interactions with neighbouring galaxies, star formation and burn galaxies is that the HI-rich up the HI. Another explanation are formed density actually in lower regions. M. Zwaan, M. Meyer, R. Webster (University of Melbourne); L. Staveley-Smith, B. Koribalski (ATNF) and the B. Koribalski (ATNF) (University of Melbourne); L. Staveley-Smith, R. Webster M. Zwaan, M. Meyer, team HIPASS An unbiased census of hydrogen in hydrogen of census unbiased An Universe the local An unbiased census of hydrogen in hydrogen of census unbiased An in hydrogen of census unbiased An Universe the local Universe the local

Astronomy reports pole isinthecentre oftheimage. neutral hydrogen massofthesources. Thedashed linemarkedwithb=0istheGalacticplane.Thesouth celestial distances ofthesources, inthesense thatredder colourscorrespond tohigherdistances.Thesymbolsize indicates the Figure 24 galaxies. conversion tostarsinthedisksof indicatingthegradual from 10%itspresentage, neutralgas only isapproximately 0.038%. This fivedensity isonly timeslower thanatthetimewhenUniverse was theUniverse, mass theneutralgas thecriticaldensityof at thepresentepoch. Expressedasafraction of massdensity theneutralgas earlier, much andallows forapreciseevaluation poorerdeterminations, of with agreement new HImassfunctionisingood theHImassfunctiontodate.This of measurement containingthe1,000brightestdetections,Bright GalaxyCatalogue resulted inthemostaccurate HIPASS, the thefirstproductsof oneof differentmasses.An analysisof distributed over of galaxies HIPASS structure, fromstudyingthelarge-scale Apart measuringexactlyhow HIis isusefulfor The distributionofextragalacticHIPASS sources inthesouthernskey. Thecolourcodingcorresponds tothe page 33

Astronomy reports ) and σ page 34 The two-point correlation function for HIPASS galaxies, plotted as a function of transverse ( galaxies, plotted as a function HIPASS function for The two-point correlation The projected real space correlation function for HIPASS and 2dF galaxies. The HI-selected galaxies function for HIPASS space correlation real The projected ) pair separation. π Figure 26 the 2dF galaxy survey. than galaxies found in clustered less strongly are Figure 25 radial (

Astronomy reports The Souther The Souther spiral arm. theouter may beadistantextensionof This emission. of theHIdiskasathinridge of detect theedge interestingfeaturesinthisimage. Atlarge, positive velocities (<100kilometrespersecond)we number of the plane. dataallow These ustotracespiralfeatures outtoGalacticradius30kiloparsecs. area There HIin emission, shown inFigure28.We of thishigh-resolutionimage combinealmost10,000spectrafor HI Using datafromtheentireSGPSIregionwe have of createdanewlongitude–velocity diagram intheISM. structure thesmallscale tothecoolphaseandthesemay much of accountfor returns gas instabilities that onlyafewparsecs. these It is through onscalesof this shellwe have instabilitystructures detectedgas overparsecs indiameterandextends above akiloparsec andbelow theGalacticplane.Along thewalls of chimney shown onthecover, was discovered GSH277+00+36, intheSGPSI;itismorethan600 fromthediskintohalo. theGalacticplaneandexpelhotgas The supernovae, canbreak outof stellarwindsand objects,These ISM. by of which thecombinedeffects arebelieved tobeformed objectsinthe thelargest which aresomeof thisreport), and chimneys theoneoncover (including of HIshells, bubbles newandexciting SGPSisproducingmany The results. work The studiesof includes oneKelvin. kilometre persecondandasensitivity limitof one onearcminute, aspectralresolutionof HI intheentireGalacticplanewithanangularresolutionof the anatlasof thiscollaborationistoconstruct GalacticPlaneSurvey.International of ultimategoal The the toform hemisphere GalacticplanemadewithtelescopesinCanada,theUSA,andGermany thenorthern of hasbeencombinedwithtwoThe SGPS data surveys ionic medium. Way theMilky andthemagneto- of continuum fieldstructure thatwe areusingtostudythemagnetic We theISM. inthe alsohave information fullpolarisation hydrogen theneutral componentof of distribution dynamics, aretounderstandthestructure, andthermal thesurvey of goals general 27. The dataset thatissensitive toallangularscalesfromtwo arcminutes toseveral inFigure asillustrated degrees, fromtheParkes radiotelescope provides spacinginformation a andshort from theCompactArray high-resolutiondata thisregion. Additionally, the combinationof sensitivity over of previous surveys magnitude improvement inbothangularresolutionand SGPSconstitutesmorethananorderof The anticipated inmid-2004. along theGalacticmidplanetolongitude+20degrees. SGPSIIisinprogress, withcompletion The second phase, SGPSII,which covers regionaroundtheGalacticCentreandextends a100square-degree a spanningGalacticlongitudesfrom253to358degrees. In2002we began latitudes –1to+1degrees), ontheGalacticmidplane(Galactic centred 210squaredegrees the survey, SGPSI,covered anareaof Way. theMilky of firstpart intheplaneof The 335squaredegrees hydrogen lineinaregion of spectral the21-cmcontinuum emissionandatomic (SGPS),aimstoimage GalacticPlaneSurvey the Southern Way. Milky theISMinSouthern the ATNF hasbeeninvolved project, This of survey inalarge-scale limited.However, theISMisremarkably thepastfive for years theatomicphaseof of thermodynamics thedynamicsand studieswithradiotelescopes, of ourknowledge Despite some50years of theinterstellarmedium(ISM). Way Milky The studyingthephysics of for provides theclosest laboratory B. Gaensler(Harvard University, USA) N. McClure-Griffiths (ATNF); J.Dickey(UniversityofMinnesota,USA); A. Green (University ofSydney); The Souther The Souther The Souther n GalacticPlaneSur n GalacticPlaneSur n GalacticPlaneSur n GalacticPlaneSur n GalacticPlaneSur page 35 vey vey vey vey vey

Astronomy reports page 36 A cross-section of the Milky Way as seen at a wavelength of 21 cm. The upper figure is an image made figure as seen at a wavelength of 21 cm. The upper of the Milky Way cross-section A Figure 27 of 14 observing the 21 cm line with an angular resolution by the Parkes telescope with the multibeam receiver and latitudes of –1.5 to +1.5 Galactic longitudes of 266 to 280 degrees, is from covered The area arcminutes. as area per second. The lower image shows the same velocity of +73 kilometres of rest at a local standard degrees In both of 2 arcminutes. data, with an angular resolution Array seen with a combination of Parkes plus Compact while black shows no atomic hydrogen, to bright emission from images, the light yellow colour corresponds the disk is warped toward where far outside the solar circle, emission. This velocity plane traces the outer Galaxy, latitude). The broad, with zero negative latitudes in this longitude range (note that the bright ridge does not align from giant shells resulting dark channel that bisects the disk on the right-hand side is a superposition of many stellar winds and explosions. From the SGPS data we have measured the rotation measured curve have of we the SGPS data From Figure 29. This in shown the inner Galaxy, of a number produced; it shows curve sampled HI rotation densely is the most ever In new results. particular see strong departures we associated with the spiral smooth circular rotation from arms, which theory gas expect that we a to spiral density wave According approaching with dotted lines. are marked spiral arm the arm before in circular velocity a decrease the inner Galaxy side should show from and then an increase as the gas passes through the arm. This in the Milky see is almost exactly we what Way.

Astronomy reports enters aspiralarmandthenbegins toincrease asthegaspassesthrough thearm. (N), Scutum-Cruxarm(Sc)and theSagittarius-Carinaarm(Sa).Therotational velocitydecreases asthegas shows theapproximate positionsand widthsofthespiralarmswhichare labelledfrom lefttorightasNorma arm Figure 29 degrees. Sagittarius-Carina spiralarmisapparent asaloopofstrong emission(very pink)crossing nearlongitude280 outer edgeoftheHIdisk(atlarge positivevelocities).We are alsoabletotracetheoutermostspiralarms.The solar circle, whereas negativevelocities showgasintheinnerGalaxy. Usingthisimagewecansearch forthe There are approximately 10,000pixelsalongthelongitudeaxis.Positivevelocitiescorrespond togasoutsidethe Figure 28 HI rotation quadrant), sampledevery arcminute. fortheinnerGalaxy(fourth curve Thedottedline Longitude–velocity imageoftheHIemissioninGalacticplane over theentire SGPSIregion. page 37

Astronomy reports