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the _ einstein _ satellite discovered x - ray emitting gas halos around luminous early type galaxies ( eg . forman , jones , & tucker 1985 ) , forcing the rejection of previous assumptions that elliptical galaxies are gas poor systems . the x - ray surface brightness distribution was found to closely follow the optical image ( trinchieri , fabbiano , & canizares 1986 ) ; however the x - ray luminosity , and hence the mass of the hot gas , showed large scatter from galaxy to galaxy ( eg . canizares , fabbiano , & trinchieri 1987 ) . the estimated cooling time of the hot gas is less than the hubble time ( trinchieri et al . 1986 ) , however cooling may be balanced by heating mechanisms such as supernova explosions . arnaud et al . ( 1992 ) found that the iron mass in the intracluster medium ( icm ) is directly proportional to the optical luminosity from early type galaxies in clusters of galaxies . this leads one to suspect that metals in the icm originate in early type galaxies and that there might be a link , in the form of early star formation and galactic winds , between the icm and metal abundances in early type galaxies . due to the poor energy resolution of previous satellites , however , critical parameters for investigating the nature of the hot gas in early type galaxies , such as the gas temperature , mass , and metal abundance have not been well - constrained . accordingly , several important issues including the origin , heating , and fate of the hot gas , and the effect of early type galaxies on the icm , are not well understood . _ asca _ ( tanaka et al . 1994 ) is the first satellite with sufficient energy resolution and large effective area over the broad 0.4 to 10 kev bandpass to determine these physical parameters . with this satellite , awaki et al . ( 1994 ) analyzed 3 early type galaxies and found that the temperature and metal abundance of the hot gas are about 0.8 kev and 0.4 solar , respectively . the inferred metal abundance is lower than expected from theoretical models , and lower than those determined at other wavelengths . accordingly , the _ asca _ observations raise a serious challenge to standard models for the evolution of galaxies and clusters of galaxies . this mystery deepened with the discovery of even lower metallicities ( less than 0.2 solar ) in two other elliptical galaxies ( loewenstein et al . 1994 ) , and in the outer regions of ngc4636 ( mushotzky et al . 1994 ) . matsushita et al . ( 1994 ) discovered , analyzing 5 early type galaxies including the sample of 3 in awaki et al . ( 1994 ) , a hard x - ray component at energies above a few kev in addition to the hot gas component dominating below about 2 kev . in order to perform plasma diagnostics of the hot gas component , it is essentially important to estimate and remove the hard component from the x - ray spectra of early type galaxies . if the hard component is due to the integrated emission of stellar sources , as suggested by matsushita et al . ( 1994 ) , its luminosity should be proportional to optical luminosity . since the samples in previous studies are too limited to fully investigate all the issues mentioned above , we have systematically studied twelve early type galaxies , including the samples of awaki et al . ( 1994 ) and matsushita et al . ( 1994 ) as well as newly observed galaxies . these comprise the largest sample of _ asca _ spectra of early type galaxies yet investigated . the galaxies we have selected for this study are ngc4472 , ngc4406 , ngc4636 , ngc4649 , ngc499 , ngc507 , ngc720 , ngc4374 , ic4296 , ngc4382 , ic1459 and ngc4365 , which are listed in table 1 with their optical parameters . the sample , which includes 7 performance and verification ( pv ) phase targets and 3 first - round guest investigator observations by the first author ( hm ) , was principally selected on the basis of soft x - ray fluxes measured with the _ einstein _ satellite in order to obtain useful spectra in reasonable exposure times . in addition to this criterion , a number of low x - ray luminosity galaxies were intentionally selected in order to detect and study possible differences between gas - rich and gas - poor galaxies . furthermore , we selected our sample to include both galaxies in dense and tenuous gaseous environments in order to be able to study possible interaction between the icm and interstellar medium ( ism ) . all the galaxies were observed with two solid - state imaging spectrometers ( sis0 and sis1 ) and two gas imaging spectrometers ( gis2 and gis3 ) at the foci of 4 thin - foil x - ray mirrors ( xrt ) on board the _ asca _ satellite . details of the instruments can be found in burke et al . ( 1991 ) , ohashi et al . ( 1996a ) , makishima et al . ( 1996 ) , and serlemitsos et al . ( 1995 ) , while a general description of _ asca _ can be found in tanaka et al . ( 1994 ) . in table 2 , we summarize the _ asca _ observation log of our sample galaxies . the data were screened with the standard selection criteria : data affected by the south atlantic anomaly , earth occultation , and regions of low geomagnetic rigidity were excluded . we also eliminated contamination by the bright earth , removed hot and flickering pixels for the sis data , and applied rise - time rejection to exclude particle events for the gis data . after the above data screening , we extracted x - ray spectra from circular regions centered on each galaxy with a uniform physical extraction radius of 38 kpc the largest radius completely contained within the sis field - of - view for all galaxies . the background spectra were obtained from source free regions around each galaxy . in order to utilize the @xmath1 technique , we rebinned the x - ray spectra to contain at least 20 counts in each spectral bin , then simultaneously fitted the spectra from the sis0 , sis1 , gis2 and gis3 , with a common normalization factor but separate response functions for each detector , using the xspec ( version 8.50 ) spectral fitting package . awaki et al . ( 1994 ) reported that the sis spectra of bright early type galaxies , ngc4636 , ngc4472 and ngc4406 exhibit emission lines from highly ionized fe , si , and s atoms . we further confirmed the presence of these emission lines in the spectra of the additional bright galaxies ngc4649 , ngc499 , ngc507 and ngc4374 . therefore we inferred that thin hot plasma emission is prevalent in bright early type galaxies and , hence , attempted to fit the x - ray spectra with a single temperature thermal plasma model ( raymond & smith 1977 ; hereafter rs model ) modified by interstellar absorption . the free parameters were the plasma temperature , metal abundance , photoelectric absorption column density , and normalization . the abundances are collectively varied keeping the relative ratio at the solar value ( anders & grevesse 1989 ) . this model , however , failed to reproduce the observed spectra except that of ngc499 . from all galaxies , systematic excess emission is found above the 4 kev band . a typical example , ngc4649 , is shown in figure 1 . thus we found the presence of hard x - ray emission , as previously reported in several individual galaxies ( kim , fabbiano & trinchieri 1992 ; matsushita et al . 1994 ) , to be a ubiquitous property of elliptical galaxies . in figure 2 we compare the x - ray spectra of the two elliptical galaxies ngc4636 and ngc4365 ; although they have nearly identical optical blue luminosities , the former is x - ray bright and the latter is x - ray faint . the difference in x - ray flux is confined to the soft x - ray band : the x - ray spectrum of ngc4636 below 3 kev is nearly two orders of magnitude brighter than that of ngc4365 . on the other hand , the x - ray spectra above the 4kev band are indistinguishable , as might be expected based on the identical optical blue band magnitudes . thus we compared the x - ray spectra above the 4 kev band for the entire sample , and found no evidence of significant differences in spectral shape , although the absolute fluxes vary from galaxy to galaxy . accordingly , we assumed a thermal bremsstrahlung model for the hard component to estimate the temperature variation using the data above 4 kev . since the statistics are limited , however , we could only determine a lower limit on the temperature of the bremsstrahlung model of about 2 kev . since the gis has higher sensitivity than the sis in the relevant high energy band , we co - added all of the gis spectra in our sample to improve the statistical accuracy . figure 3 shows the composite gis 2 and 3 spectra above the 4 kev band . we fitted a thermal bremsstrahlung model to this spectrum , and obtained an acceptable fit ( @xmath2 of @xmath3 ) with the best - fit temperature @xmath4 kev ( hereafter , errors are 90 % confidence unless otherwise stated ) . this composite spectrum is equally well fitted ( @xmath2 of 22.83/31 ) by a power law model with photon index 1.8@xmath5 . therefore , we can not distinguish between the two possible origins  thermal and non - thermal  of the hard component from the spectrum alone . however the relevant physical parameters , such as the x - ray luminosity ( @xmath6 ) of the hard component , or iron k - shell line flux do not significantly differ whether we use thermal bremsstrahlung or power - law models . thus we assume the thermal - bremsstrahlung model for further discussion .    in order to estimate the strength of fe k line emission , we added a gaussian line to the above model . the best - fit temperature is slightly altered to @xmath7 kev , with line center energy and equivalent width of the gaussian of @xmath8 kev and @xmath9 ev , respectively . confidence contours of the line energy and equivalent width at @xmath10 2.71 , 4.61 and 9.21 are plotted in figure 4 . adding the line decreased @xmath1 from 22.36 to 18.50 , which is not statistically significant ( malina , lampton & bowyer 1976 ) . therefore we can conclude that the composite hard component spectrum requires no significant emission lines .    since the presence of both emission lines from highly ionized heavy elements in the low energy band and a hard x - ray tail at the high energy band seem to be common in the galaxies in our sample , we fitted two - component models to all broad band spectra . the models consist of a thermal bremsstrahlung component with a fixed temperature of 12 kev determined from the composite hard band spectrum , plus a thin thermal model ( rs model ) for the soft band emission . the column density of the hard component was constrained to be the same as that of the rs model . the free parameters were the temperature and metal abundance of the rs model , the column density , and normalizations for both the rs and bremsstrahlung models . the best - fit parameters and 90% confidence errors are listed in table 3 . we generally found reasonable fits with this unified model , however two galaxies  ngc4636 and ngc507  exhibit unacceptably large values of @xmath1 . although these two galaxies may require more complicated modeling ( ngc4636 was found to have both an abundance gradient and an extra centrally concentrated cool component by mushotzky et al . 1994 ) , more detailed study of individual galaxies is beyond the scope of this paper . the best - fit rs abundances and temperatures are in excellent agreement with those derived from _ rosat _ pspc observations ( davis & white 1996 ; kim & fabbiano 1995 ) , except for ngc4472 where the _ asca _ parameters are consistent only with the central pspc parameters ( forman et al . significant excess absorption is required by the _ asca _ , but not the pspc , spectra of ngc4472 , ngc4406 , and ngc4649 . this discrepancy is likely due either to remaining inaccuracies in the _ asca _ low energy response , or to the inadequacy of the simple foreground screen model that we employ for the absorption . many authors have pointed out systematic differences in the best - fit parameters between models using different plasma emission codes . we thus examined this possible systematic and model - dependent uncertainty by comparing the rs and meka models ( mewe , r. , gronenschild , e.h.b.m . , and van den oord , g.h.j . 1985 ) . in figures 5a  d , we show the correlation plots of best - fit parameters between the rs and meka models : the column density ( a ) , temperature ( b ) , metal abundance ( c ) , and x - ray luminosity ( d ) . the best - fit column densities are found to be consistent within the errors , while best - fit temperatures in the meka model are almost 20 % lower than the rs model . the metal abundances in the meka model generally have larger values than the rs model , although the scatter in the correlation plot is large . as for the luminosity , both models give essentially the same best - fit value . thus we confirmed the existence of plasma model - dependent systematic and non - systematic errors . however these do not largely effect the following discussion , hence we refer to the best - fit values using the rs model . figure 6 shows the relation between the x - ray luminosity ( @xmath6 ) of the hard component in the 0.54.5 kev band and the blue band luminosity ( @xmath11 ) . the uncertainties in @xmath6 of the hard component are typically @xmath1230% . the solid line is the best - fit relation between the blue luminosity and the 0.54.5 kev band luminosity found for bulge - dominated spiral galaxies ( canizares et al . we found that @xmath6 of the hard component is proportional to @xmath11 , and that the constant of proportionality is nearly the same as found in spiral galaxies : @xmath13 for the hard component in early type galaxies is generally consistent with that of bulge - dominated spiral galaxies like m31 . the excess hard flux in the radio galaxies ic1459 and ic4296 probably can be explained by x - ray emission from agn ; indeed our analysis of archival pspc data from ic1459 indicates the presence of an unresolved hard component . furthermore , we found that the composite _ asca _ gis spectrum above the 4kev band ( section 3 ) resembles the x - ray spectra of bulge - dominated spiral galaxies which can be fitted with a thermal bremsstrahlung model with @xmath14 kev ( eg . makishima et al . 1989 ) . these facts suggest that early type galaxies contain a hard x - ray component attributable to the same origin as x - rays in bulge - dominated spiral galaxies . since the x - ray emission from bulge - dominated spirals is thought to arise from a population of low - mass x - ray binaries ( lmxb ) , we suspect that the primary hard component in early type galaxies is also due to the integrated emission of an ensemble of lmxb . matsushita et al . ( 1994 ) came to the same conclusion based on a more limited ( 5 galaxies ) sample ; they also discovered that the hard component is generally extended which argues against an agn power - law origin for the hard component . with a larger galaxy sample than matsushita et al . ( 1994 ) , we therefore confirm that both the shape and relative magnitude of the hard component in early type galaxies is consistent with that in bulge - dominated spiral galaxies , strengthening the suggestion that the hard x - ray component in early type galaxies is due to lmxb . although lmxb usually exhibit a weak 6.7 kev iron line , we found no significant iron line in the early type galaxies . the 90 % confidence upper limit on the equivalent width of the fe k@xmath15 line of 500 ev is too large to place any strong constraints on the lmxb scenario . emission lines from highly ionized fe , si , and s are detected from the 7 galaxies in our sample with the best statistics ; non - detection of emission lines for the other galaxies is consistent with their having a lower signal - to - noise ratio . the existence of these emission lines is direct evidence for the prevalence of thin hot interstellar plasma in bright early type galaxies . we now discuss the nature of this plasma using our results , as well as referring to published optical data .      because @xmath6 of the hard component is generally proportional to @xmath11 , the large dispersion in the total @xmath6-@xmath11 diagram ( canizares et al . 1987 ) is mainly due to a spread in @xmath6 of the soft component . this is illustrated in figure 7 where @xmath6 of the soft component is plotted versus @xmath11 . since , ignoring the mostly small variations in temperature , @xmath6 of the soft component is proportional to the volume emission measure ( @xmath17 ) , and @xmath18 , where @xmath19 and @xmath20 are the densities of electrons and protons , respectively , and @xmath21 and @xmath22 are , respectively , the volume and mass of the hot gas , the large dispersion in @xmath6 found in figure 7 indicates the presence of a wide mass range of hot gas in early type galaxies . figure 8 is a plot of the volume emission measure ( @xmath17 ) versus the temperature of the hot gas . for comparison , we show the data for clusters of galaxies in the same figure with plus symbols ( hatsukade 1989 ) . the spearman rank correlation coefficient between @xmath17 and temperature for early type galaxies is estimated to be 0.43 ; therefore , we can not conclude that there is a strong correlation between temperature and mass of the hot gas . the line in the figure shows the best - fit relation for the cluster data . what is clear is the fact that most of our galaxy sample is located well below the cluster correlation line , and that @xmath17 drops steeply with @xmath16 from rich cluster all the way down to galaxy scales . since for a constant gas mass as a fraction of gravitational mass @xmath17 @xmath23 , it is clear that early type galaxies are far more gas poor than clusters . figure 9 presents the relation between the stellar velocity dispersion and the hot gas temperature . the velocity dispersions of the galaxies in clusters are shown with plus signs ( hatsukade 1989 ) . the solid line represents @xmath24 , where @xmath25 , and @xmath26 , @xmath27 , @xmath28 , @xmath29 and @xmath30 are mean molecular weight ( we assumed it to be 0.6 ) , proton mass , stellar ( or galaxy ) velocity dispersion , boltzmann constant , and temperature , respectively . @xmath24 indicates that the thermal energy of the hot gas per unit mass is equal to the stellar ( or galactic ) kinetic energy per unit mass . the spearman rank correlation coefficient for early type galaxies between @xmath28 and temperature is estimated to be 0.54 , which is not significant . thus we can not strongly conclude that there is a positive correlation between these two parameters which would indicate a correlation between the depth of the gravitational potential and the temperature of the hot gas as expected for equilibrium systems . however , all our sample galaxies show higher temperatures than would be expected based on the best - fit cluster sample correlation line ; _ i.e. _ @xmath0 is less than 1 for all of the early type galaxies in our sample compared to approximately 1 for clusters of galaxies . in other words , the thermal energy of the hot gas per unit mass is larger than the stellar kinetic energy per unit mass . figure 10 shows the relation between the velocity dispersion and @xmath0 . the mean value of @xmath0 , weighted using relative errors , is about 0.5 . if the stars and gas in early type galaxies are both isothermal and in hydrostatic equilibrium , @xmath31 , where @xmath32 and @xmath33 are the densities of hot gas and stars in the galaxy , respectively ( eg . sarazin 1986 ) . trinchieri et al . ( 1986 ) have found that for bright early type galaxies , the x - ray and optical surface brightness tend to follow each other . since the x - ray brightness profile traces @xmath34 and the optical profile traces @xmath33 , this implies that @xmath0 is about 0.5 ( fabbiano 1989 ) , consistent with our direct measurement of @xmath0 . @xmath35 is expected if cooling ( proportional to @xmath34 ) is approximately balanced by heating by stellar winds , gravitational compression in an inflow , or type ia supernovae that all scale as the local stellar density . assuming that the present - day stellar mass loss rate is about @xmath36 and has decreased with time as @xmath37 ( ciotti et al . 1991 ) , we see that the typical mass of hot gas observed in early type galaxies ( @xmath38 ) is much less than the total accumulated over the hubble time ( @xmath39 ) . this fact in conjunction with @xmath35 and the short cooling times of the hot gas in the central regions ( @xmath40  10@xmath41 yr ; fabbiano 1989 ) implies that either ( 1 ) there is some heating mechanism that balances cooling and has driven much of the stellar mass loss out of the galaxy , or ( 2 ) an inflow is occurring where the primary heating mechanism is gravitational compression and where there must be some sink for gas cooling below x - ray emitting temperatures .    one may argue that a plausible heating mechanism is type ia supernova explosions . we consider a simple model where the energy of supernova explosions is constant ( @xmath42 erg ) and the energy deposited per unit gas mass uniform over the entire galaxy . let @xmath43 be the `` excess temperature ''  the difference between the temperature of the hot gas and that corresponding to the stellar velocity dispersion , @xmath44 since we are considering emission from a standard volume , the mass of the hot gas is proportional to the square root of @xmath17 ( section 4.1.1 ) , and the supernova rate thought to be proportional to @xmath11 . if heating by type ia supernovae is important , we would expect a negative correlation between @xmath43 and @xmath45 because the rise in gas temperature should be smaller as the gas mass per supernova becomes larger . figure 11 shows the plot of @xmath45 vs. @xmath43 . since the spearman rank correlation coefficient is 0.40 , we can conclude that there is no negative correlation . this contradicts simple models where the heating source is proportional to @xmath11 and the efficiency of heating is uniformly high , but rather suggests that the efficiency of energy transfer to the hot gas may increase as the gas mass per star becomes larger . a negative correlation between @xmath45 and fe abundance would also be predicted by a simple snia - dominated heating model ( see below ) , and is likewise not seen . the importance of heating by type ia supernovae can generally be ruled out on the basis of the observed constraints on the iron abundance , since each explosion injects @xmath46 of fe into the hot gas . this means that increasing the gas temperature by @xmath47 kev will enhance the fe abundance by @xmath48 in solar units . even if we attribute all of the fe in the hot gas to supernova explosions an extreme assumption considering the expected contribution from stellar mass loss ( section 4.2.3 )  supernova heating can not explain the observed values of @xmath43 in most of our sample . figure 12 shows the relation between the abundance and the temperature . we can see no clear correlation between these parameters , although the lowest metallicities are found in the galaxies with the coolest ism . if we use the meka model , these conclusions are not essentially altered .    for the galaxies whose metal abundances are well determined , the abundances , without exception , are found to be less than half solar . these values are considerably lower than theoretical expectations , and those determined at optical wavelengths . an abundance gradient ( mushotzky et al . 1994 ) may partially account for the discrepancy between optical abundances , which are determined in the central region of the galaxy , and x - ray abundances measured over a region extending to many effective radii . significantly sub - solar metallicities have also been observed with _ asca _ in a variety of sources , including stellar coronae ( eg . singh , drake , & white 1995 ) , starburst galaxies . awaki et al . 1995 ; tsuru et al . 1996 ) , and supernova remnants ( snrs ) ( eg . hayashi et al . 1996 ) . we think it is worth noting that some snrs in the large magellanic cloud sufficiently evolved to sweep up large amounts of ism exhibit x - ray spectra which closely resemble those of early type galaxies ( hayashi et al . 1996 ) . improvements in our understanding of the processes of enrichment by supernovae and stellar mass loss may help solve the puzzle of low abundances if , for example , the gas ejected from supernovae does not mix well into the ism and the gas which is overly dense and metal - rich cools and drops out of the x - ray emitting hot gas ( fujita , fukumoto , & okoshi 1996 ) . arimoto et al . ( 1996 ) suggest that low abundances may be an artifact , since the metal abundance is constrained by fe l emission lines around 1 kev for which the atomic physics parameters are poorly known . however , hwang et al . ( 1996 ) have found that , for hot gas temperatures between 2 and 4 kev , the abundance determined from fe l and fe k lines is fairly consistent ( with abundances determined from the fe l region actually slightly higher ) , and any errors in the abundances due to atomic physics uncertainties that exist in the current codes are unlikely to exceed 30  50 % . therefore plasma model uncertainties may not explain the low abundances , although the increasing complexity of fe l emission for temperatures below 1 kev imply that more detailed analysis than lies within the scope of this paper is needed to solve this problem . we note that the consistency of fe abundances derived independently over a wide range of ionization states in stellar coronae ( eg . drake 1996 ) and the comparably low abundances inferred for ions with more straightforward atomic parameters ( eg . si ; ohashi et al . 1996b ) implies that it is unlikely that the abundances derived here are underestimated by large factors . weak constraints on oxygen abundances are available only for the 3-brightest early type galaxies ( ngc4472 , ngc4406 , and ngc4636 ) ; other galaxies have insufficient signal - to - noise ratios . the best fit oxygen abundances for the 3 galaxies we derive are consistent with those found by awaki et al . ( 1994 ) , roughly equal to the iron abundances . the oxygen abundances are not determined to sufficient accuracy to place significant constraints on the relative contributions of snii and snia to the heavy metal production in the observed galaxies . our sample includes galaxies in both relatively dense and tenuous intergalactic environments . ngc4636 , for example , is very far from the center of the virgo cluster and no nearby icm x - ray emission is seen , while ngc4472 , the central galaxy of a subgroup in the virgo cluster , is surrounded by significant icm x - ray emission . ngc720 , at the center of the poor group lgg38 ( garcia 1993 ) , on the other hand , does not show effects from either ram pressure or tidal distortion , hence is regarded as rather isolated ( buote & canizares 1996 ) .    for all the correlations shown in figures 6  12 , we see no systematic differences between the galaxies in dense and tenuous gaseous environments . this indicates that the interaction between the icm and ism is not strong enough to manifest itself in our sample . more comprehensive investigations of such interactions require detailed study of spatial variations in x - ray spectral properties as in iwasawa et al . ( 1996 ) who have found evidence for ram pressure stripping of the ism in ngc4406 , as well as a larger sample spanning a wider range of environments . we have presented results from the uniform analysis of the _ asca _ spectra of 12 early type galaxies . this is the largest such sample to date and , as summarized below , we have uncovered new facts as well as confirmed previous inferences based on much smaller samples .    1 .   we found that the x - ray spectra from the 12 galaxies in our sample generally consist of at least two components : a soft component from x - ray emission of hot gas , and a hard component that can be characterized by either a thermal bremsstrahlung model with @xmath49 kev or a power - law model of photon index 1.8 . the consistency of the strength and spectral shape of the hard component with those in bulge - dominated spirals corroborates previous suggestions that it primarily originates as the integrated emission from x - ray binaries . the hard component spectrum requires no significant fe k line emission , and the upper limit on the equivalent width of fe k line emission is 460 ev . we confirmed that the metal abundance of the hot gas is generally less than 0.5 solar . there is no clear correlation between the abundance and temperature of the hot gas , however the lowest abundances are found in the coolest galaxies . there is a large dispersion in the ratio of gas mass ( _ i.e. _ the x - ray luminosity of the soft component ) to optical luminosity , implying a wide variety of gas - dynamical histories . 4 .   theories of large - scale structure imply that there is a continuum of dark matter halos spanning galaxy and cluster scales . however , we have found that early type galaxies fall well below the constant gas mass fraction extension of the hottest clusters in the @xmath50 plane ( vem @xmath23 ) , and that the ratio of thermal to kinetic energy per unit mass is , on average , twice that found for clusters of galaxies . this suggests that larger systems are generally more efficient at retaining their hot gas and less efficient at converting gas into stars . the interstellar media of elliptical galaxies are not simply scaled down version of intracluster media , but have been more profoundly effected by feedback from star formation and other gas - dynamical processes . the low fe abundances , as well as the absence of a negative correlation between the `` excess temperature '' , defined as the difference between the hot gas temperature and the temperature corresponding to the stellar velocity dispersion , and the ratio of the square root of the volume emission measure of the hot gas to the blue band luminosity ( an indicator of the mass ratio of hot gas to stars ) argue against type ia supernovae being an important heat source for the ism . we found no systematic differences in the physical parameters of the hot gas between galaxies in dense and tenuous intracluster environments , although our ability to test this is limited . this indicates that interaction between the intracluster medium and interstellar matter may not be strong .    in short , _ asca _ analysis of early type galaxies has yielded both expected ( a hard component with the same normalization as in spiral bulges ) and unexpected ( low interstellar abundances ) results . the interrelationships and dispersion among the properties of the hot gas component , and their comparison with those in intracluster media demonstrates the relative importance of astration , mass loss , and gas - dynamics in determining the evolution of early type galaxies and their ism . any complete theory of galaxy formation must explain the observed trends and diversity of bound distributions of hot gas on galaxy and cluster scales . awaki , h. , tsuru , t. , koyama , k. , & _ asca _ team 1996 , in uv and x - ray spectroscopy of astrophysical and laboratory plasmas , ed . yamashita , k. , and watanabe , t. ( tokyo , japan : universal academy press , inc . ) , 327                                                                                  lcccccccccc ngc4472(m49 ) & 12 29 46.5 & 07 59 58 & 25.8 & 9.26 & -22.80 & 11.28 & e2 & 315 & 1.6e20 & virgongc4406(m86 ) & 12 26 11.8 & 12 56 49 & 25.8 & 9.71 & -22.35 & 11.10 & e3 & 256 & 2.7e20 & virgongc4636 & 12 42 49.8 & 02 41 17 & 25.8 & 10.37 & -21.69 & 10.84 & e0 - 1 & 217 & 1.9e20 & virgongc4649(m60 ) & 12 43 40.3 & 11 32 58 & 25.8 & 9.70 & -22.36 & 11.11 & e2 & 344 & 2.4e20 & virgongc499 & 01 23 11.6 & 33 27 36 & 94.5 & 12.79 & -22.09 & 11.00 & s0@xmath51 & 235 & 5.3e20 & piscesngc507 & 01 23 40.1 & 33 15 22 & 94.5 & 12.19 & -22.69 & 11.24 & sa(r)0@xmath52 & 306 & 5.3e20 & piscesngc720 & 01 53 00.4 & -13 44 21 & 39.6 & 11.13 & -21.86 & 10.91 & e5 & 224 & 1.4e20 & lgg38ngc4374(m84 ) & 12 25 03.7 & 12 53 15 & 25.8 & 9.91 & -22.15 & 11.02 & e1 & 296 & 2.6e20 & virgoic4296 & 13 36 38.9 & -33 57 59 & 72.8 & 11.42 & -22.89 & 11.32 & e & 290 & 4.3e20 & hg22ngc4382(m85 ) & 12 25 24.7 & 18 11 27 & 25.8 & 9.95 & -22.11 & 11.01 & sa(s)0@xmath53 & 200 & 2.7e20&virgoic1459 & 22 57 10 & -36 27 42 & 43.0 & 10.83 & -22.34 & 11.10 & e3 - 4 & 316 & 1.2e20 & hg15ngc4365 & 12 24 27.9 & 07 19 06 & 25.8 & 10.42 & -21.64 & 10.82 & e3 & 262 & 1.6e20 & virgo    lllrlllllllll ngc4472 & 1993/07/04 & 5 & b & 4 & 20.1 & 20.1 & 21.5 & 21.5 & 0.39 & 0.31 & 0.13 & 0.16ngc4406 & 1993/07/03 & 5 & f & 4/2 & 19.7 & 19.7 & 20.8 & 20.8 & 0.34 & 0.27 & 0.11 & 0.13ngc4636 & 1993/06/22 & 5 & b & 4 & 38.3 & 38.4 & 37.6 & 37.6 & 0.38 & 0.27 & 0.090 & 0.092ngc4649 & 1994/01/07 & 5 & f & 4/2 & 38.8 & 38.8 & 38.8 & 38.8 & 0.18 & 0.11 & 0.070 & 0.072ngc499 & 1994/01/23 & 1.4 & f & 2 & 28.0 & 28.1 & 38.9 & 38.8 & 0.031 & 0.031 & 5.1e-3 & 8.8e-3ngc507 & 1994/01/23 & 1.4 & f & 2 & 28.0 & 28.1 & 38.9 & 38.8 & 0.052 & 0.039 & 0.020 & 0.016ngc720 & 1993/07/17 & 3.3 & b & 4 & 34.9 & 35.0 & 36.3 & 36.3 & 0.033 & 0.026 & 8.7e-3 & 0.011ngc4374 & 1993/07/04 & 5 & b & 4/2 & 19.3 & 19.4 & 20.5 & 20.5 & 0.048 & 0.088 & 0.020 & 0.037ic4296 & 1994/02/15 & 1.8 & f & 2 & 35.8 & 35.8 & 37.1 & 37.1 & 0.025 & 0.018 & 8.5e-3 & 0.010ngc4382 & 1994/05/27 & 5 & f & 2/1 & 33.1 & 33.4 & 35.3 & 35.3 & 0.045 & 0.035 & 0.011 & 0.013ic1459 & 1993/05/20 & 3 & b & 4 & 19.5 & 19.5 & 19.3 & 19.3 & 0.043 & 0.032 & 0.016 & 0.018ngc4365 & 1993/06/28 & 5 & b & 4 & 35.7 & 35.7 & 36.5 & 36.5 & 0.019 & 0.019 & 0.013 & 0.015    lccccccccccccc ngc4472 & 13.4 & 0.89 & 0.39 & 5.9 & 5.5e-12 & 9.0e-13 & 6.2e41 & 8.4e40 & 442.1/425 & ( 11.315.5 ) & ( 0.880.90 ) & ( 0.330.45)&(5.26.7 ) ngc4406 & 10.9 & 0.84 & 0.31 & 6.3 & 5.6e-12 & 4.2e-13 & 6.0e41 & 3.9e40 & 708.3/616 & ( 8.513.0 ) & ( 0.830.86 ) & ( 0.260.38 ) & ( 5.27.3 ) ngc4636 & 4.9 & 0.76 & 0.31 & 5.0 & 5.9e-12 & 3.9e-13 & 5.4e41 & 3.3e40 & 732.9/428 & ( 3.66.3 ) & ( 0.750.77 ) & ( 0.280.35 ) & ( 4.45.6 ) ngc4649 & 16.1 & 0.85 & 0.34 & 2.7 & 2.3e-12 & 7.1e-13 & 2.8e41 & 6.8e40 & 605.7/545 & ( 13.019.7 ) & ( 0.830.86 ) & ( 0.280.44 ) & ( 2.23.3 ) ngc499 & 7.8 & 0.71 & 0.25 & 21.3 & 1.5e-12 & @xmath541.2e-13 & 2.0e42 & @xmath541.4e41 & 123.0/115 & ( 1.016.1 ) & ( 0.670.76 ) & ( 0.180.47 ) & ( 12.826.6 ) ngc507 & 10.7 & 1.01 & 0.29 & 33.0 & 1.9e-12 & 2.5e-13 & 2.6e42 & 3.1e41 & 317.0/177 & ( 6.4 - 15.6 ) & ( 0.961.05 ) & ( 0.200.42 ) & ( 24.542.6 ) ngc720 & 0.0 & 0.65 & 0.098 & 1.9 & 5.5e-13 & 2.2e-13 & 1.0e41 & 4.1e40 & 150.3/139 & ( @xmath541.3 ) & ( 0.610.68 ) & ( 0.0690.14 ) & ( 1.52.5 ) ngc4374 & 12.1 & 0.67 & 0.052 & 3.5 & 1.2e-12 & 4.7e-13 & 1.4e41 & 4.3e40 & 274.9/317 & ( 3.320.0 ) & ( 0.590.81 ) & ( 0.0290.12 ) & ( 1.75.5 ) ic4296 & 6.8 & 0.84 & 1.1 & 1.1 & 3.7e-13 & 4.5e-13 & 2.8e41 & 3.1e41 & 139.7/110 & ( @xmath5427.0 ) & ( 0.790.88 ) & ( @xmath550.32 ) & ( 0.183.7 ) ngc4382 & 19.0 & 0.28 & 0.056 & 4.3 & 3.7e-13 & 5.3e-13 & 7.3e40 & 5.2e40 & 280.4/217 & ( 0.4332.5 ) & ( 0.220.33 ) & ( 0.029 - 0.21 ) & ( 0.5318.3 ) ic1459 & 0.0 & 0.71 & 0.17 & 0.64 & 2.2e-13 & 7.2e-13 & 4.8e40 & 1.6e41 & 84.11/109 & ( @xmath544.1 ) & ( 0.64 - 0.79 ) & ( @xmath550.065 ) & ( 0.0241.4 ) ngc4365 & 0.0 & 0.56 & 0.12 & 0.11 & 8.4e-14 & 3.9e-13 & 6.6e39 & 3.1e40 & 200.2/218 & ( @xmath5432.8 ) & ( 0.22 - 0.72 ) & ( @xmath550.016 ) & ( 0.00228.7 )
we have systematically investigated the _ asca _ 
 spectra of 12 early type galaxies . 
 this paper presents the global spectral properties of these systems based on a larger sample than in any previous _ asca _ study . 
 the x - ray spectra were uniformly fitted by a two - component model consisting of hard x - rays from thermal emission with a temperature of about 10 kev or from a power - law with index 1.8 , plus soft x - rays from a thin thermal plasma with temperature ranging from 0.3 to 1 kev . 
 the x - ray luminosities of the hard component are found to be proportional to the blue band luminosities , while those of the soft component show large scatter with no clear correlation . 
 the metal abundances determined from the soft component are systematically lower than solar , with a mean value of about 0.3 solar . 
 we examine the relationships between the temperature and volume emission measure , and between the gas temperature and the stellar velocity dispersion . 
 the volume emission measures for early type galaxies plotted as a function of the gas temperature are well below the extrapolated line found in clusters of galaxies , indicating that early type galaxies are relatively gas poor compared with galaxy clusters . 
 the ratio of the stellar kinetic energy per unit mass to the thermal energy of the hot gas per unit mass ( @xmath0 ) is less than unity . 
 we found no systematic relationship between x - ray properties and environment , suggesting that the interaction between interstellar matter and the intracluster medium is not strong .