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high - mass stars ( m@xmath14m@xmath9 ) are predominantly observed in young ( @xmath15myr ) , massive clusters ( m@xmath16m@xmath9 ) located within giant molecular clouds ( gmcs ) . despite their rarity and short life times , high - mass stars are responsible for injecting a significant amount of energy into the interstellar medium ( ism ) by means of stellar winds , ionising radiation and supernovae . the impact of such feedback mechanisms from high - mass stars on the ism and star formation is still a topic of debate but is thought to play an important role in driving the evolution of gmcs . feedback can be both constructive and destructive by sweeping up and clearing out parsec - scale cavities ( or bubbles ) in the ism @xcite resulting in dense gas shells or destroying and dispersing the molecular environment . this means that feedback from high - mass stars should have the potential to both inhibit or enhance subsequent star formation and profoundly influence the star formation history ( sfh ) of gmcs @xcite . the g305 gmc complex is located within the scutum - crux arm of the milky way at @xmath17 , @xmath18 at a distance of @xmath19kpc and is one of the most massive and luminous star - forming regions in the galaxy @xcite . the g305 complex consists of a number of molecular clouds that surround a cavity centered on the open clusters danks1 and 2 ( fig . [ im : obsmopra ] , triangles ) and the wolf rayet star wr48a . the feedback from the high - mass stars in and around danks1 and 2 appears to be responsible for driving the expansion of a large ( @xmath20pc ) cavity into the surrounding molecular gas . previous observations of g305 , summarised by @xcite , have revealed the presence of ongoing star formation surrounding the central cavity ( see fig.2 in @xcite ) , which suggests that the overall morphology of the complex is consistent with numerous sites of ongoing high - mass star formation that may have been triggered by interaction between the winds and ionising radiation of danks1 and 2 and the natal molecular clouds . these conditions make g305 an excellent laboratory in which to study high - mass star formation and the impact of feedback from high - mass stars on the evolution of gmcs .    in this work we present single dish observations of @xmath0co , @xmath1co  and c@xmath2o  in the rotational transition to explore the global distribution and properties of molecular gas in g305 . co is the most abundant molecule in the ism , after h@xmath3 , and the low - energy rotational transition is an excellent tracer of the cool ( @xmath21k ) low density gas ( @xmath22@xmath23 ) within molecular clouds @xcite . to explore the ionised environment we present wide - area interferometric observations of the large - scale 5.5 and 8.8ghz radio continuum which is generated by the thermal bremsstrahlung mechanism in the ionised gas that surrounds high - mass stars . previous observations of the radio continuum emission towards g305 have been limited to low resolution ( 45 ) single dish observations @xcite that are unable to resolve the radio substructure on the scale of compact hii regions . higher resolution ( 1 - 20 ) interferometric radio continuum observations exist but suffer from low sensitivity and significant spatial filtering @xcite and so are unable to identify extended features . the data set presented in the following section allows the investigation of the molecular environment in which high - mass star formation is ongoing and allows us to trace the distribution and investigate the impact of ionising radiation from high - mass stars . by searching the literature for tracers of ongoing star formation , we are able to investigate the relationship between the ionised and molecular environment with star formation and thus broadly trace the sfh of the region . this paper is organised as follows ; in section  [ sect : obs ] we present the observations , data reduction and ancillary data utilised in this study , section  [ sect : results ] presents the results and analysis of the molecular and ionised observations , in section  [ sect : discussion ] we present our discussion of the results including the relationship between the ionised and molecular gas and star formation , the role of triggering and sfh of the region . we end this paper with a summary in section  [ sect : summary ] . co observations of the g305 complex were obtained during two observing runs in september of 2010 and 2011 using the 3 mm receiver on the mopra 22-m millimetre - wave telescope operated by the australia telescope national facility ( atnf ) . the back end of mopra is the university of new south wales mopra spectrometer ( mops ) which consists of four 2.2ghz bands that overlap to provide 8ghz of continuous bandwidth . the narrow or `` zoom '' mode of mops was used which allows 16 intermediate frequencies ( ifs ) to be observed simultaneously . each of the 16 zoom `` windows '' has a bandwidth of 137.5mhz over 4096 channels giving a velocity resolution at 110ghz of @xmath24kms@xmath13  per channel . the velocities presented in this work are in the kinematic local standard of rest ( lsr ) frame centred on @xmath25kms@xmath13 , the systematic velocity of g305 @xcite . we centred the 8ghz band at 112ghz and placed the zoom windows of mops to cover three co isotopologues ; @xmath0co , @xmath1co  and c@xmath2o  in the rotational transition ( table  [ tab : mopslines2 ] ) . the remaining zoom windows were set to the rest frequency of lines of interest such as hc@xmath26n ( ) , ch@xmath26cn ( ) and c@xmath27o ( ) but no emission @xmath28 , where @xmath29 is the rms background noise , was detected .
we present 109115ghz ( 3 mm ) wide - field spectral line observations of @xmath0co , @xmath1co  and c@xmath2o   molecular emission and 5.5 and 8.8ghz ( 6 and 3 cm ) radio continuum emission towards the high - mass star forming complex known as g305 . 
 the morphology of g305 is dominated by a large evacuated cavity at the centre of the complex driven by clusters of o stars surrounded by molecular gas . 
 our goals are to determine the physical properties of the molecular environment and reveal the relationship between the molecular and ionised gas and star formation in g305 . 
 this is in an effort to characterise the star - forming environment and constrain the star formation history in an attempt to evaluate the impact of high - mass stars on the evolution of the g305 complex . 
 analysis of co emission in g305 reveals 156 molecular clumps with the following physical characteristics ; excitation temperatures ranging from 725k , optical depths of 0.20.9 , h@xmath3 column densities of @xmath4@xmath5@xmath6 , clump masses ranging from @xmath7@xmath8m@xmath9  and a total molecular mass of @xmath10m@xmath9 . 
 the 5.5 and 8.8ghz radio continuum emission reveals an extended low surface brightness ionised environment within which we identify 15 large - scale features with a further eight smaller sources projected within these features . by comparing to mid infrared emission and archival data , we identify nine hii regions , seven compact hii regions , one region , four extended regions . 
 the total integrated flux of the radio continuum emission at 5.5ghz is @xmath11jy corresponding to a lyman continuum output of @xmath12photonss@xmath13 . 
 we compare the ionised and molecular environment with optically identified high - mass stars and ongoing star formation , identified from the literature . 
 analysis of this dataset reveals a star formation rate of 0.0080.016m@xmath9yr@xmath13  and efficiency of 712% , allows us to probe the star formation history of the region and discuss the impact of high - mass stars on the evolution of g305 . 
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