Deuterium astration in the local disc and beyond
a r X i v :a s t r o -p h /0603190v 1 8 M a r 2006
Mon.Not.R.Astron.Soc.000,1–10(2006)Printed 5February 2008
(MN L A T E X style ?le v1.4)
Deuterium astration in the local disc and beyond
Donatella Romano,1?Monica Tosi,1Cristina Chiappini 2,3and Francesca Matteucci 4
1INAF –Osservatorio
Astronomico di Bologna,Via Ranzani 1,I-40127Bologna,Italy
2INAF –Osservatorio Astronomico di Trieste,Via Tiepolo 11,I-34131Trieste,Italy
3Geneva Observatory,1290Sauverny,Switzerland 4Dipartimento di Astronomia,Universit`a di Trieste,Via Tiepolo 11,I-34131Trieste,Italy
Accepted 2006March 7.Received 2006March 7;in original form 2006January 19
ABSTRACT
Estimates of the interstellar deuterium abundance span a wide range of values.Until recently,
it was customary to adopt the abundance of deuterium measured in the Local Bubble as rep-resentative of the local one.Now,it is becoming unclear whether the true local deuterium abundance is signi?cantly higher or lower than this value,depending on the interpretation given to current data.It is important to deal with the issue of the deuterium variation and see whether it challenges our current understanding of the Galaxy evolution.To this aim,we study the evolution of deuterium in the framework of successful models for the chemical evolution of the Milky Way able to reproduce the majority of the observational constraints for the solar neighbourhood and for the Galactic disc.We show that,in the framework of our models,the lowest D/H values observed locally cannot be explained in terms of simple astration processes occurring during the Galaxy evolution.Indeed,the combination of a mild star formation and a continuous infall of unprocessed gas required to ?t all the available observational data allows only a modest variation of the deuterium abundance from its primordial value.Therefore,we suggest that depletion of deuterium on to dust grains is the most likely physical mechanism proposed so far to explain the observed dispersion in the local data.
Key words:cosmology:observations –Galaxy:abundances –Galaxy:evolution –ISM:abundances
1INTRODUCTION
Deuterium is created during primordial nucleosynthesis (e.g.Wein-berg 1977;Boesgaard &Steigman 1985;Olive,Steigman &Walker 2000)and then destroyed in stars through D (p,γ)3He reactions oc-curring at relatively low temperatures (of a few 105K).Since it is hard to synthesize this loosely bound isotope in signi?cant quanti-ties in any astrophysical environment (Epstein,Arnett &Schramm 1976;Epstein 1977;Prodanovi′c &Fields 2003),its abundance in galaxies is expected to monotonically decrease with time owing to stellar cycling.
Deuterium is the light nuclide produced during Big Bang Nu-cleosynthesis (BBN)whose primordial abundance is most tightly tied to the baryon-to-photon ratio,η(or,equivalently,to the ra-tio of the baryon and critical densities at the present time,?b ).In principle,once its primordial abundance,(D/H)p ,is derived from measurements in unevolved systems,the value of ?b is precisely known.However,there is still signi?cant dispersion among the abundances derived for a handful of high-redshift,low-metallicity absorption-line systems towards quasi-stellar objects (QSOs)with reasonably ?rm deuterium detections.A more precise ηdetermina-?E-mail:donatella.romano@oabo.inaf.it (DR);monica.tosi@oabo.inaf.it (MT);chiappini@ts.astro.it (CC);matteucci@ts.astro.it (FM)tion comes from the observations of the cosmic microwave back-ground (CMB)power spectrum coupled to Ly αforest data (Spergel
et al.2003;see,however,Pettini 2006,his ?g.7).The suggested
value,η10=6.1+0.3?0.2,where η10≡1010η=274?b h 2
,when coupled to predictions from standard BBN theory,leads to a very narrow range for the primordial deuterium abundance,(D/H)p ?2.4–2.8×10?5(e.g.Coc et al.2004).
Relating (D/H)p to the current local abundance of D meets with the non-trivial issue of estimating what the true local abun-dance of deuterium actually is.In fact,a large scatter is found among nearly ?fty D/H measurements towards as many Galactic lines of sight.Possible explanations (including deuterium deple-tion on to dust grains,or recent infall of unprocessed gas;see e.g.Pettini 2006,and references therein;Prochaska et al.2005)lead to different interpretations of the data.
Up to some years ago,models for the chemical evolution of the Galactic disc were used to bound the primordial D mass frac-tion.Studies of this kind were motivated by the widely differing (by an order of magnitude)observational estimates of (D/H)p published in the literature,coming from a few high-redshift QSO absorption spectra.It was crucial then to infer (D/H)p from the D abundance observed in the solar system and the interstellar medium (ISM)as-suming the astration factor required to reproduce the largest set of available observational data.In general,it was found that (D/H)p
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Table1.D/H measurements towards QSOs.A weighted mean of these data(except measurements towards Q0347?3819and PKS1937?1009at z abs= 3.256;see text for details)gives D/H =2.6±0.3(the error in the mean is the dispersion about the mean divided by the square root of the number of data points),a value consistent with the primordial abundance inferred from the CMB power spectrum and the standard BBN theory.
PKS1937?1009(I)LL17.86±0.02 3.572(3.3±0.3)×10?5?2.7,?1.9b Burles&Tytler1998a Q1009+2956LL17.39±0.06 2.504 3.98+0.59
×10?5?2.4,?2.7c Burles&Tytler1998b
?0.67
HS0105+1619LL19.422±0.009 2.536(2.54±0.23)×10?5?1.85?2.0O’Meara et al.2001 Q2206?199DLA20.436±0.008 2.0762(1.65±0.35)×10?5?2.23Pettini&Bowen2001 Q0347?3819DLA20.626±0.005 3.025(3.75±0.25)×10?5?0.95±0.02Levshakov et al.2002 Q1243+3047LL19.76±0.04 2.526 2.42+0.35
×10?5?2.79±0.05Kirkman et al.2003
?0.25
×10?5?2.0±0.5Crighton et al.2004 PKS1937?1009(II)LL18.25±0.02 3.256 1.6+0.25
?0.30
Sembach et al.2004 PG1259+593HVC19.95±0.050.0(2.2±0.7)×10?5?0.79+0.12
?0.16
Deuterium astration
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Figure 1.Available measurements of D/H in QSO absorption systems from Table 1.The abundance of deuterium is plotted against metallicity (ei-ther [Si/H]–open symbols,or [O/H]–?lled ones).There are no hints of decreasing D/H with increasing metallicity.Rather,a large dispersion is present across the whole metallicity range.The weighted mean of the data (except for measurements towards Q 0347?3819and PKS 1937?1009at z abs =3.256;see text for details)is also shown (solid line)with its errors (dashed lines).
ments include that in the high-velocity,low-metallicity gas cloud Complex C falling on to the Milky Way,also listed in Table https://www.wendangku.net/doc/1512454977.html,ing Far Ultraviolet Spectroscopic Explorer (FUSE)and Hub-ble Space Telescope (HST)observations of the QSO PG 1259+593,Sembach et al.(2004)detect D I Lyman series absorption in Complex C and derive (D/H)Complex C =(2.2±0.7)×10?5,(O/H)Complex C =(8.0±2.5)×10?5,and (D/O)Complex C =0.28±0.12.A value consistent with the primordial deuterium abundance, D/H =(2.3±0.4)×10?5(weighted mean for three regions at Galactic longitudes l =171?,183?,195?),is found also from the 327MHz D line,for a Galactocentric distance of R G =10±1kpc (Rogers et al.2005).
Precise measurements of D/H in the local interstellar medium (LISM)were obtained with Copernicus (e.g.Rogerson &York 1973),HST (e.g.Linsky 1998),and the Interstellar Medium Ab-sorption Pro?le Spectrograph (IMAPS;Jenkins et al.1999;Son-neborn et al.2000).In recent years,FUSE has added many deter-minations of D/H (as well as D/O and D/N)along several lines of sight probing the neutral ISM up to ～2.7kpc away (e.g.Moos et al.2002;H′e brard &Moos 2003;Wood et al.2004;H′e brard et al.2005;Oliveira et al.2006).As data accumulated,the situation got complicated.Within the Local Bubble (LB;a low-density region within a distance of ～100pc in which the Sun is embedded),D/H is nearly constant.However,while Wood et al.(2004)state that (D/H)LB =(1.56±0.04)×10?5,a value derived from N (D I )and N (H I )measurements towards 16targets,H′e brard &Moos (2003),who rely on measurements of D/O and O/H,?nd (D/H)LB =(1.32±0.08)×10?5,a value signi?cantly lower.At log N (H I )>～20.5(i.e.,distances greater than 500pc),the few data points available up to now display a low deuterium abundance,D/H =
(0.85±0.09)×10?5,while in the intermediate range [d ～100–500pc;log N (H I )=19.2–20.7]the D/H ratio is found to vary from ～0.5×10?5to ～2.2×10?5(see,e.g.,Linsky et al.2005).This behaviour is interpreted as due to deuterium depletion on to dust grains (Linsky et al.2005;see also Prochaska et al.2005;Oliveira et al.2006),following an original idea by Jura (1982).According to this picture,the most representative value for the total (gas plus dust)D/H ratio within 1kpc of the Sun would be (D/H)LISM ≥(2.19±0.27)×10?5(Linsky et al.2005).On the other hand,on the basis of D/O and O/H measurements,H′e brard &Moos (2003)suggest that the low D/H value at ‘large’distances truly re?ects the present-epoch D/H.In their scenario,(D/H)LISM should be lower than 1×10?5.
Solar system observations of 3He permit an indirect determi-nation of the deuterium abundance in the Protosolar Cloud (PSC;Geiss &Reeves 1972).Such an estimate of the deuterium abun-dance 4.5Gyr ago,(D/H)PSC =(2.1±0.5)×10?5(Geiss &Gloeckler 1998),is remarkably similar to both the primordial and the local D/H values,if the highest D/H values measured by FUSE represent the actual abundance of deuterium in the vicinity of the Sun.It is worth noticing that measures of deuterium in the atmo-sphere of Jupiter using the Galileo Probe Mass Spectrometer give a similar value,(D/H)PSC =(2.6±0.7)×10?5(Mahaffy et al.1998).
Finally,detection of deuterium in a molecular cloud at 10parsecs from the Galactic Centre indicates that (D/H)GC =(1.7±0.3)×10?6(Lubowich et al.2000),?ve orders of magni-tude larger than the predictions of GCE models with no continuous source of deuterium in the bulge (Matteucci,Romano &Molaro 1999).This discrepancy is suggestive of some replenishment pro-cess,likely infall of gas of cosmological composition (Lubowich et al.2000;Audouze et al.1976).
3GALACTIC EVOLUTION OF DEUTERIUM
Once the primordial abundance of deuterium is settled thanks to (ei-ther direct or indirect)observations,the knowledge of the present-day Galactic deuterium abundance is needed to establish the degree of astration suffered by deuterium in the Milky Way.This in turn has profound implications for our understanding of the mechanisms of the formation and evolution of the Galaxy.3.1The solar neighbourhood
If (D/H)p =(2.6±0.3)×10?5,and (D/H)LISM ≥(2.19±0.27)×10?5according to Linsky et al.(2005),then a low astration factor,f ≤1.2±0.3,is required.On the other hand,if (D/H)LISM =(0.85±0.09)×10?5,as argued by H′e brard &Moos (2003),then f ?3.1±0.7.Here f is the astration factor by number,f =
(D /H)p
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Figure 2.Theory versus observations.The abundance of deuterium measured in QSO absorbers (circles)is plotted against metallicity (either [Si/H]–upper panel,open circles;or [O/H]–lower panel,?lled circles).Only the systems with ?rm D detections are considered (see Table 1for references and Section 2for discussion).Also shown are the deuterium abundance in the PSC (Geiss &Gloeckler 1998;upper and lower panels;Sun symbol)and those representative of the true D/H in the LISM (lower panel,squares),according to either Linsky et al.(2005;‘high’value)or H′e brard &Moos (2003;‘low’value).The values of O/H in the LISM are those measured by Oliveira et al.(2005)for the neutral ISM inside the LB,log(O/H)+12=8.54±0.02,and Esteban et al.(2004)for Orion (ionized gas plus dust),log(O/H)+12=8.73±0.03.Notice that the Oliveira et al.measurement refers to the gas phase only,and thus misses ～25per cent of the total oxygen due to depletion on to dust grains.Theoretical predictions (upper panel:D/H versus [Si/H];lower panel:D/H versus [O/H])refer to models for the solar vicinity computed with different prescriptions about the stellar lifetimes and IMF:Scalo’s (1986)IMF and Maeder &Meynet’s (1989)stellar lifetimes (solid line);Kroupa et al.’s (1993)IMF and Maeder &Meynet’s (1989)stellar lifetimes (dot-dashed line);Scalo’s (1986)IMF and Schaller et al.’s (1992)stellar lifetimes (dotted line);Kroupa et al.’s (1993)IMF and Schaller et al.’s (1992)stellar lifetimes (dashed line).See Romano et al.(2005a)for details about the models.All ratios are normalized to the solar abundances of Asplund et al.(2005).
is due to the combination of a moderate star formation and a con-tinuous infall of external gas during the whole Galactic disc evo-lution.Noticeably,this result is almost independent of the speci?c GCE code used (either that developed by Tosi 1988a,b;or that de-veloped by Chiappini et al.1997,2002).Higher astration factors (f ～2–3)were suggested in the past (e.g.Galli et al.1995;Prant-zos 1996;Fields 1996;but see also Chiappini et al.1997;Tosi et al.1998).The low one reported here is mainly due to the adoption of an updated stellar metallicity distribution,which needs more in-fall in order to be reproduced.Having that much infall,it comes out really hard to get larger astration factors.As stressed above,in Romano et al.(2003)we adopted the mean D/H value measured by Linsky (1998)in the LB,(D/H)LB =(1.50±0.10)×10?5,as representative of the deuterium abundance in the solar vicinity at the present time.This assumption seems now to be no longer valid in the light of recent,contrasting interpretations of the dispersion
terium by mass at t =0and t =t now =13.7Gyr,respectively.F is larger than f by a few per cent,because of hydrogen burning into helium and heavier species in the course of the Galaxy’s evolution.
in the local data (see discussions in Section 2).Therefore,in this section we recompute the evolution of D/H.
First,we adopt various prescriptions for the stellar lifetimes and initial mass function (IMF)in a successful model for the chem-ical evolution of the Milky Way.Details about the model can be found in Chiappini et al.(2002)and Romano et al.(2005a),where results relevant to several chemical species are discussed.Notice that here we consider only those (IMF,stellar lifetimes)combina-tions which proved to guarantee a good ?t to all the observational constraints available for the Milky Way (see Romano et al.2005a).The aim is to associate a ‘theoretical error’to our estimate of f .
In Fig.2we show model predictions for D/H versus [Si/H](upper panel)and D/H versus [O/H](lower panel)in the solar neighbourhood obtained with:
(i)the Scalo (1986)IMF and the Maeder &Meynet (1989)stel-lar lifetimes (solid line);
(ii)the Kroupa et al.(1993)IMF and the Maeder &Meynet (1989)stellar lifetimes (dot-dashed line);
(iii)the Scalo (1986)IMF and the Schaller et al.(1992)stellar lifetimes (dotted line);
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Deuterium astration5 Table2.Theoretical astration factors for deuterium.Listed are the astration
factors by number,f,suitable for comparison with the observations.Dif-
ferent astration factors are predicted when assuming differing formulations
for the stellar lifetimes and IMF in the GCE code.
Scalo(1986)Maeder&Meynet(1989) 1.52
Kroupa et al.(1993)Maeder&Meynet(1989) 1.83
Scalo(1986)Schaller et al.(1992) 1.39
Kroupa et al.(1993)Schaller et al.(1992) 1.61
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Figure 4.Models aimed at reproducing the lowest (D/H)LISM values
disagree with other important observational constraints.For instance,the model displayed in this ?gure (solid lines)assumes a very short time scale for thin-disc formation in the solar neighbourhood (τD =1.5Gyr),at vari-ance with common assumptions (see Chiappini et al.1997).Hence,while a lower (D/H)LISM can be attained (upper panel),the G-dwarf metallic-ity distribution of solar neighbourhood stars can not be reproduced any more (lower panel).Also shown for comparison are the predictions of a successful model (τD =7Gyr;dotted lines),which well reproduces the shape of the observed G-dwarf metallicity distribution.This model leads to a higher (D/H)LISM value.The observed G-dwarf metallicity distributions (histograms in the lower panel)are from Wyse &Gilmore (1995;dashed histogram),Rocha-Pinto &Maciel (1996;dotted histogram)and J?rgensen (2000;solid histogram).Also shown is the K-dwarf metallicity distribu-tion by Kotoneva et al.(2002;big dots).The theoretical distributions are convolved with a Gaussian (σ=0.1)to account for the observational and intrinsic scatter.
well reproduces all the other observational constraints (Romano et al.2005a).
In general,our models predict (D/H)LISM values in the range 1.4–2.0×10?5.We need to enhance the ratio of the star formation to gas infall ef?ciencies if a larger fraction of the initial deuterium has to be destroyed.But can a more ef?cient star formation and/or less effective infall of unprocessed gas be accommodated within successful GCE models?It is immediately seen that the almost con-stant metal abundance of the ISM from the time of Sun’s formation
up to now (Esteban et al.2004)sharply contrasts with rapid star formation and/or absence of external sources of unenriched gas.In Fig.4,we show the outputs of a model especially designed to pro-duce a signi?cant drop in deuterium abundance from its PSC value to the local one (for further modeling and discussions see Tosi et al.1998).This model,assuming τD =1.5Gyr rather than 7Gyr for the thin-disc formation time scale,?ts the solar and local ‘low’D/H values (Fig.4,upper panel,solid line),as well as other obser-vational constraints (such as for instance the current gaseous and stellar mass surface densities at the solar position).However,it is barely consistent with the metal abundances of the Sun,it pred-its a sharp increase of the metal abundance of the ISM in the last 4.5Gyr (at variance with the observations),and it can not account for the metallicity distribution of solar neighbourhood G-and K-dwarf stars (Fig.4,lower panel,solid line).The metallicity distri-bution of long-lived stars in the solar neighbourhood is a fundamen-tal constraint for GCE models,which mainly constrains the infall time scale and strength (see,e.g.,Chiappini et al.1997;Matteucci 2004).In Fig.4,lower panel,we show as a dashed,dotted,and solid histogram the G-dwarf metallicity distributions observed by Wyse &Gilmore (1995),Rocha-Pinto &Maciel (1996)and J?rgensen (2000),respectively.Also shown is the K-dwarf metallicity distri-bution by Kotoneva et al.(2002;big dots).K dwarfs have lifetimes older than the present age of the Galactic disc,and are thus ideal stars for investigating the chemical evolution of the disc.G dwarf stars instead are suf?ciently massive that some of them have begun to evolve away from the main sequence,so that corrections must be taken into account when determining their space densities and metallicity (Kotoneva et al.2002).These corrections are at least partly responsible for the non-negligible differences among differ-ent observational G-dwarf metallicity distributions (in particular,the low-metallicity tail of the distribution and the exact position of the peak may vary signi?cantly according to different authors).In conclusion,in the framework of our models we can not explain at the same time both the lowest observed (D/H)LISM values and the observed G-and K-dwarf metallicity distributions.3.2Present-day abundance gradients
In Fig.5we display the Galactic gradients of D/H,D/O,and O/H at the present time predicted by adopting the prescriptions of Model A of Chiappini et al.(2001)as far as the formation and evolution of the Galactic disc are concerned,and by varying the prescriptions for the IMF and the stellar lifetimes (solid line:Scalo’s 1986IMF and Maeder &Meynet’s 1989stellar lifetimes;dashed line:Kroupa et al.’s 1993IMF and Maeder &Meynet’s 1989stellar lifetimes;dotted line:Scalo’s 1986IMF and Schaller et al.’s 1992stellar life-times –see Romano et al.2005a).A value of (D/H)p =2.6×10?5is assumed for all the models.Also shown are the relevant obser-vations.The ?lled squares in the upper panel of Fig.5stand for the representative D/H value in the LISM according to either Linsky et al.(2005;‘high’value)or H′e brard &Moos (2003;‘low’value).The ?lled triangle in the same panel refers to the measurement by Rogers et al.(2005)for the outer Galactic disk.The ?lled squares in the middle panel of Fig.5stand for the representative D/O ratio ac-cording to either H′e brard &Moos (2003;lower value)or Linsky et al.(2005;higher value).To obtain (D/O)LISM in this latter case,we divided (D/H)LISM from Linsky et al.(2005)by the oxygen abun-dance of Orion (Esteban et al.2004).At ?rst glance,it seems that GCE models explain the lowest D/O value better than the high-est one,while the opposite is true for D/H (upper panel).How-ever,one should recall that the current oxygen abundance displays
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Figure 5.Present-day distributions of D/H (upper panel),D/O (middle panel)and log(O/H)+12(lower panel)along the disc of the Galaxy.Predictions from models assuming either the Scalo (1986)IMF and the Maeder &Meynet (1989)stellar lifetimes (solid line),or the Kroupa et al.(1993)IMF and the Maeder &Meynet (1989)stellar lifetimes (dashed line),or the Scalo (1986)IMF and the Schaller et al.(1992)stellar lifetimes (dotted line)are shown together with the relevant observations.Upper panel,?lled squares:representative D/H value in the LISM according to Linsky et al.(2005;‘high’value)and H′e brard &Moos (2003;‘low’value);?lled triangle:deuterium measurement from the 327MHz D line in the outer disc (Rogers et al.2005).Middle panel,?lled squares:representative D/O value in the LISM according to H′e brard &Moos (2003;‘low’value)and Linsky et al.(2005;‘high’value –in this case the oxygen abundance measured by Esteban et al.2004for Orion has been taken as representative of the total oxygen content of the LISM).Also shown (big star)is the D/O ratio towards LSE 44measured by Friedman et al.(2006;see discussion in the text).Lower panel,small ?lled circles:compilation of log(O/H)+12versus R G data from Chiappini et al.(2001);?lled square:oxygen abundance in Orion from Esteban et al.(2004).
a non-negligible spread.Indeed,several indicators –H II regions,B-type stars,the neutral medium –show that the local oxygen abun-dance varies in the range 8.3≤log(O/H)+12≤9.0(Fig.5,lower panel,and Oliveira et al.2006,their table 12).So,in Fig.5,mid-dle panel,we show also the D/O ratio recently measured by Fried-man et al.(2006)for the line of sight towards LSE 44.Along this
line of sight,(D/H)LSE 44=2.24+0.70?0.67×10
?5
,consistent with the lower limit suggested by Linsky et al.(2005),and (O/H)LSE 44=
11.3+4.8?3.6×10
?4
(that is the highest O/H value measured locally by FUSE ).Now,within the errors,the model adopting the Scalo (1986)IMF and the Schaller et al.(1992)stellar lifetimes is in satisfactory agreement with both the observed ‘high’(D/H)LISM and ‘low’(D/O)LISM ,provided that (D/O)LISM is ‘low’as a conse-quence of both a high deuterium and a high oxygen abundance in the LISM.
It is seen that the shape of the gradients slightly changes when changing the prescriptions about the IMF and the stellar lifetimes.In the Galactocentric distance range R G =4–12kpc the theoretical gradients of log(D/H),log(D/O),and log(O/H)+12are 0.03±0.01dex kpc ?1,0.08dex kpc ?1,and ?0.055±0.005dex kpc ?1,re-spectively.In the outermost regions of the disc the gradient of D/H
?attens,while those of D/O and O/H steepen,owing to the lower and lower amount of gas processed by stars outward in the disc.Before concluding that,according to GCE model predictions,one shall observe D/H ratios close to the primordial value at the largest radii in spiral galaxies,it is worth reminding that the model predictions depend on a number of uncertain free parameters.Model A of Chiappini et al.(2001)produces a fairly steep O/H gradient at the largest radii (Fig.5,bottom panel),while the ma-jority of the data suggest a ?atter behaviour.A ?atter O/H gradient in the outer disc is easily obtained by suppressing the gas density threshold which regulates the star formation process during the pre-ceding halo phase.The solid lines in Fig.6stand for Chiappini et al.’s (2001)Model C results.This model is analogous to Model A (Fig.5,solid lines),except that it allows star formation in the halo to go on even when the gas density drops below the threshold value (～4M ⊙pc ?2).The expected D/H ratio is now ～2.5×10?5at the outermost radii,i.e.below the adopted primordial value [(D/H)p =2.9×10?5for this model].Also shown in Fig.6are the predictions from the model of Tosi et al.(in preparation),which is an updated
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Figure 6.Same as Fig.5,but for Model C of Chiappini et al.(2001;solid lines)and for the model of Tosi et al.(in preparation),which is an updated version of the model of Tosi (1988a,b)extended to the whole disc (dashed and dotted lines).Here (D/H)p =2.9×10?5(solid and dashed lines)or 2.3×10?5(dotted lines),and not 2.6×10?5.
version of the model by Tosi (1988a,b)adopting the Kroupa et al.(1993)IMF and the Schaller et al.(1992)stellar lifetimes,and ex-tending to the whole disc [dashed lines:(D/H)p =2.9×10?5;dot-ted lines:(D/H)p =2.3×10?5].This model tends to predict higher oxygen abundances,hence lower D/O ratios,across the disc.
We conclude that,in principle,accurate measurements of both D/H and O/H in the outermost regions of spiral galaxies can al-low us to discriminate among existing scenarios of galaxy for-mation and evolution.In fact,only minor uncertainties related to the adopted stellar yields affect the interpretation of the data in this case,owing to the well-known nucleosynthetic origin of both species.Hence,observational efforts in this direction are highly de-sirable.
In summary,notice that all the GCE models discussed above favour minor deuterium variations [?log(D/H)/?R G ?0.02dex kpc ?1]in the Galactocentric distance range sampled by current observations (R G ?8–11kpc),hence favouring the highest (D/H)LIMS determinations as representative of the local deuterium abundance.
4DISCUSSION AND CONCLUSIONS
In general,observations of deuterium abundances provide lower
bounds on its primordial abundance.However,at suf?ciently high
redshifts and low metallicities,one expects the primordial abun-dance of deuterium to reveal itself as a plateau.Instead,statistically signi?cant scatter of the D/H measurements has been found in sev-eral high-redshift QSO absorbers.Before claiming that a disper-sion around the mean value is actually present,one has to carefully check possible systematics affecting the abundance derivation.It has been suggested that in the absorbers with the lowest H I column densities,interlopers might indeed contribute to the inferred D I column densities,while in those with the highest H I column den-sities,interlopers might affect the wings of the H I lines (Steigman 2004,2006,and references therein).Yet,it is worth noticing that the placement of the continuum and the ?tting of the damping wings are closely related for DLAs:if one gets the continuum wrong,it is unlikely that he could ?t the line pro?le satisfactorily (M.Pet-tini,private communication).In this paper,we assume (D/H)p =(2.6±0.3)×10?5,i.e.the weighted mean of D/H measurements towards QSOs (indirect determinations give a consistent value;see discussions in Sections 1and 2).
Of more concern is the dispersion of local D/H data.In the LISM,D/H is found to vary from ～0.5×10?5to ～2.2×10?5(H′e brad et al.2005;Linsky et al.2005;Williger et al.2005;Fried-man et al.2006;Oliveira et al.2006;to quote only the most recent works).Basically,two mechanisms are suggested in the current lit-erature which might explain the observed variation (Pettini 2006,
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2006RAS,MNRAS 000,1–10
Deuterium astration9
and references therein;see also Lemoine et al.1999;Prochaska et al.2005):
(i)differing ISM conditions along different sight lines,which determine different degrees of deuterium depletion on to dust grains;
(ii)localized infall of unprocessed gas,which modi?es the deu-terium abundance in the surveyed region while leaving unchanged those of more abundant species,such as oxygen.
In the?rst case,one should recover the true local D/H in interstellar clouds which have been accelerated by supernova shocks,since the depletion of refractory elements is much reduced relative to that of the normal quiescent ISM there;in this case,the true local abun-dance of deuterium would be the highest observed one(Linsky et al.2005,and references therein).In the second case,the true local abundance of deuterium would be the lowest observed one.In any case,the mean D/H value measured within the Local Bubble should not be considered any more as representative of the actual degree of astration suffered by deuterium in the solar neighbourhood.By assuming that the primordial abundance of deuterium is reasonably well known,one can usefully bind the deuterium astration factor of the solar vicinity.An astration factor(by number)either as low as f≤1.2±0.3or a factor of2–3higher is permitted by the observations.
In this paper,we have computed a number of GCE models for the solar vicinity as well as for the whole Galactic disc and conclude that:
(i)Only low astration factors(not in excess of f?1.8) are compatible with GCE requirements:our models predict (D/H)LISM=1.4–2.0×10?5starting from a primordial value of (D/H)p=2.6×10?5.This is not surprising:in the absence of supernova-driven winds which ef?ciently remove the metal-rich ejecta of dying stars from the Galaxy and/or in the absence of a peculiar IMF,the relatively high present-day gas content and low metallicity are indicative of modest astration(and,hence,modest D destruction;see also Tosi et al.1998).We emphasize here once again that the low astration factors are due to the combination of moderate star formation and continuous infall of gas which are needed in order to reproduce the available Milky Way data.
(ii)Small variations in the predicted D astration factor are pro-duced by changing the prescriptions on the IMF and the stellar lifetimes.In particular,by adopting the Scalo(1986)IMF and the Schaller et al.(1992)stellar lifetimes we predict a D astration fac-tor which clearly favours the low one suggested by Linsky et al. (2005).With this choice for the IMF and the stellar lifetimes,the model also gives a good?t to many other observational constraints for the Galaxy(Romano et al.2005a).
(iii)When the model is forced to reproduce the lowest D/H values observed locally,the agreement between model predictions and relevant observations is lost,for one or more observables(the most relevant observational constraints being–in this context–the G-dwarf metallicity distribution,the mild increase of the overall metallicity of the ISM from the time of Sun’s formation up to now, the present-day mass and gas surface densities,the present-day in-fall rate;see also Matteucci2004).
(iv)In order to attain the lowest D/H values observed in the LISM,the smooth,gentle decline which nicely accounts for the PSC D abundance,must turn into a steeper behaviour during the latest phases of Galaxy’s evolution.However,a large gas cycling through stars in the last～5Gyr is unlikely,in the light of the small increase of the global metal abundance from the time of Sun’s for-mation up to now suggested by several independent indicators(Es-teban et al.2004;their table15and references therein).
(v)In principle,joint observations of deuterium and oxygen abundances in the outermost regions of galactic discs can shed light on the mechanisms of spiral galaxy formation and evolution.
In conclusion,we favour a scenario in which D/H in the solar neigh-bourhood declines mildly during Galaxy’s evolution,due to the combined effect of moderate star formation and continuous infall of external gas.In this framework,the dispersion in the current lo-cal D/H data might be at least partly explained by different degrees of dust depletion along different lines of sight. ACKNOWLEDGMENTS
DR and MT wish to thank J.Geiss,G.Gloeckler,G.H′e brard,J. Linsky,and T.Bania of the LoLa-GE Team for useful conversa-tions at the International Space Science Institute in Bern.The warm hospitality and the?nancial support at ISSI are gratefully acknowl-edged.We are also grateful to G.Steigman for stimulating discus-sions and to W.Moos and M.Pettini for interesting conversations about many observational aspects.We thank J.Linsky and M.Pet-tini for providing us with a copy of their papers in advance of pub-lication.
REFERENCES
Andr′e M.K.,Oliveira C.M.,Howk J.C.,et al.,2003,ApJ,591,1000 Asplund M.,Grevesse N.,Sauval A.J.,2005,in Barnes T.G.III,Bash F.N., eds,ASP Conf.Ser.,Cosmic Abundances as Records of Stellar Evolu-tion and Nucleosynthesis.Astron.Soc.Pac.,San Francisco,V ol.336, p.25
Audouze J.,Lequeux J.,Reeves H.,Vigroux L.,1976,ApJ,208,L51 Boesgaard A.M.,Steigman G.,1985,ARA&A,23,319
Burles S.,Tytler D.,1998a,ApJ,499,699
Burles S.,Tytler D.,1998b,ApJ,507,732
Cartledge S.I.B.,Lauroesch J.T.,Meyer D.M.,So?a U.J.,2004,ApJ, 613,1037
Charbonnel C.,Primas F.,2005,A&A,442,961
Chiappini C.,Matteucci F.,Gratton R.,1997,ApJ,477,765
Chiappini C.,Matteucci F.,Romano D.,2001,ApJ,554,1044
Chiappini C.,Renda A.,Matteucci F.,2002,A&A,395,789
Coc A.,Vangioni-Flam E.,Descouvemont P.,Adahchour A.,Angulo C., 2004,ApJ,600,544
Crighton N.H.M.,Webb J.K.,Carswell R.F.,Lanzetta K.M.,2003,MN-RAS,345,243
Crighton N.H.M.,Webb J.K.,Ortiz-Gil A.,Fern′a ndez-Soto A.,2004, MNRAS,355,1042
Epstein R.L.,1977,ApJ,212,595
Epstein R.L.,Arnett W.D.,Schramm D.N.,1976,ApJS,31,111 Esteban C.,Peimbert M.,Garc′?a-Rojas J.,Ruiz M.T.,Peimbert A., Rodr′?guez M.,2004,MNRAS,355,229
Fields B.D.,1996,ApJ,456,478
Fields B.D.,Olive K.A.,Silk J.,Cass′e M.,Vangioni-Flam E.,2001,ApJ, 563,653
Friedman S.D.,H′e brard G.,Tripp T.M.,Chayer P.,Sembach K.R.,2006, ApJ,638,847
Galli D.,Palla F.,Ferrini F.,Penco U.,1995,ApJ,443,536
Geiss J.,Gloeckler G.,1998,Space Sci.Rev.,84,239
Geiss J.,Reeves H.,1972,A&A,18,126
H′e brard G.,Moos H.W.,2003,ApJ,599,297
H′e brard G.,Tripp T.M.,Chayer P.,et al.,2005,ApJ,635,1136
Jenkins E.B.,Tripp T.M.,Wo′z niak P.R.,So?a U.J.,Sonneborn G.,1999, ApJ,520,182
c 2006RAS,MNRAS000,1–10
10 D.Romano et al.
J?rgensen B.R.,2000,A&A,363,947
Jura M.,1982,in Kondo Y.,ed.,Advances in Ultraviolet Astronomy.Wash-ington,NASA,p.54
Kirkman D.,Tytler D.,Suzuki N.,O’Meara J.M.,Lubin D.,2003,ApJS, 149,1
Kotoneva E.,Flynn C.,Chiappini C.,Matteucci F.,2002,MNRAS,336, 879
Kroupa P.,Tout C.A.,Gilmore G.,1993,MNRAS,262,545
Lemoine M.,Audouze J.,Ben Jaffel L.,et al.,1999,New Astr.,4,231 Levshakov S.A.,Dessauges-Zavadsky M.,D’Odorico S.,Molaro P.,2002, ApJ,565,696
Linsky J.L.,1998,Space Sci.Rev.,84,285
Linsky J.L.,Draine B.T.,Moos H.W.,et al.,2005,BAAS,37,1444 Lubowich D.A.,Pasachoff J.M.,Balonek T.J.,Millar T.J.,Tremonti C., Roberts H.,Galloway R.P.,2000,Nat,405,1025
Maeder A.,Meynet G.,1989,A&A,210,155
Mahaffy P.R.,Donahue T.M.,Atreya S.K.,Owen T.C.,Niemann H.B., 1998,Space Sci.Rev.,84,251
Matteucci F.,2004,in McWilliam A.,Rauch M.,eds,Carnegie Obs.As-troph.Ser.,Origin and Evolution of the Elements.Cambridge Univ.
Press,Cambridge,p.87
Matteucci F.,Romano D.,Molaro P.,1999,A&A,341,458
Meyer D.M.,Jura M.,Cardelli J.A.,1998,ApJ,493,222
Moos H.W.,Sembach K.R.,Vidal-Madjar A.,et al.,2002,ApJS,140,3 Olive K.A.,Steigman G.,Walker T.P.,2000,Phys.Rep.,333,389
Olive K.A.,Skillman E.D.,2004,ApJ,617,29
Oliveira C.M.,Dupuis J.,Chayer P.,Moos H.W.,2005,ApJ,625,232 Oliveira C.M.,Moos H.W.,Chayer P.,Kruk J.W.,2006,ApJ in press (astro-ph/0601114)
O’Meara J.M.,Tytler D.,Kirkman D.,Suzuki N.,Prochaska J.X.,Lubin
D.,Wolfe A.M.,2001,ApJ,552,718
Pettini M.,2006,in Sonneborn G.,Moos H.W.,Andersson B.-G.,eds,ASP Conf.Ser.,Astrophysics in the Far Ultraviolet.Astron.Soc.Pac.,San Francisco,V ol.348,in press(astro-ph/0601428)
Pettini M.,Bowen D.V.,2001,ApJ,560,41
Prantzos N.,1996,A&A,310,106
Prantzos N.,Ishimaru Y.,2001,A&A,376,751
Prochaska J.X.,Tripp T.M.,Howk J.C.,2005,ApJ,620,L39 Prodanovi′c T.,Fields B.D.,2003,ApJ,597,48
Rocha-Pinto H.J.,Maciel W.J.,1996,MNRAS,279,447
Rogers A.E.E.,Dudevoir K.A.,Carter J.C.,Fanous B.J.,Kratzenberg E., Bania T.M.,2005,ApJ,630,L41
Rogerson J.B.,York D.G.,1973,ApJ,186,L95
Romano D.,Chiappini C.,Matteucci F.,Tosi M.,2005a,A&A,430,491 Romano D.,Chiappini C.,Matteucci F.,Tosi M.,2005b,in Corbelli E., Palla F.,Zinnecker H.,eds,ASSL,The Initial Mass Function50years later.Springer,Dordrecht,V ol.327,p.231(astro-ph/0409474) Romano D.,Tosi M.,Matteucci F.,Chiappini C.,2003,MNRAS,346,295 Scalo J.M.,1986,Fund.Cosmic Phys.,11,1
Schaller G.,Schaerer D.,Meynet G.,Maeder A.,1992,A&AS,96,269 Scully S.,Cass′e M.,Olive K.A.,Vangioni-Flam E.,1997,ApJ,476,521 Sembach K.R.,Wakker B.P.,Tripp T.M.,et al.,2004,ApJS,150,387 Sonneborn G.,Tripp T.M.,Ferlet R.,Jenkins E.B.,So?a U.J.,Vidal-Madjar A.,Wo′z niak P.R.,2000,ApJ,545,277
Spergel D.N.,Verde L.,Peiris H.V.,et al.,2003,ApJS,148,175 Steigman G.,1994,MNRAS,269,L53
Steigman G.,2004,in Freedman W.L.,ed.,Carnegie Obs.Astr.Ser.,Mea-suring and Modeling the Universe.Cambridge,Cambridge Univ.Press, p.169
Steigman G.,2006,Int.Journal of Modern Phys.E,15,1
Steigman G.,Tosi M.,1992,ApJ,401,150
Steigman G.,Tosi M.,1995,ApJ,453,173
Tosi M.,1988a,A&A,197,33
Tosi M.,1988b,A&A,197,47
Tosi M.,1996,in Leitherer C.,Fritze-von-Alvensleben U.,Huchra J.,eds, ASP Conf.Ser.,From Stars to Galaxies:The Impact of Stellar Physics on Galaxy Evolution.Astron.Soc.Pac.,San Francisco,V ol.98,p.299 Tosi M.,Steigman G.,Matteucci F.,Chiappini C.1998,ApJ,498,226Vangioni-Flam E.,Olive K.A.,Prantzos N.1994,ApJ,427,618 Weinberg S.,1977,The?rst three minutes.A modern view of the origin of the universe.London:Andre Deutsch
Williger G.M.,Oliveira C.,H′e brard G.,Dupuis J.,Dreizler S.,Moos H.
W.,2005,ApJ,625,210
Wood B.E.,Linsky J.L.,H′e brard G.,Williger G.M.,Moos H.W.,Blair W.P.,2004,ApJ,609,838
Wyse R.F.G.,Gilmore G.,1995,AJ,110,2771
This paper has been produced using the Royal Astronomical Soci-ety/Blackwell Science L A T E X style?le.
c 2006RAS,MNRAS000,1–10
The way常见用法
The way 的用法 Ⅰ常见用法： 1)the way+ that 2)the way + in which（最为正式的用法） 3)the way + 省略（最为自然的用法） 举例：I like the way in which he talks. I like the way that he talks. I like the way he talks. Ⅱ习惯用法： 在当代美国英语中，the way用作为副词的对格，“the way+ 从句”实际上相当于一个状语从句来修饰整个句子。 1)The way =as I am talking to you just the way I’d talk to my own child. He did not do it the way his friends did. Most fruits are naturally sweet and we can eat them just the way they are—all we have to do is to clean and peel them. 2）The way= according to the way/ judging from the way The way you answer the question, you are an excellent student. The way most people look at you, you’d think trash man is a monster. 3）The way =how/ how much No one can imagine the way he missed her. 4）The way =because
The way的用法及其含义(二)
The way的用法及其含义（二） 二、the way在句中的语法作用 the way在句中可以作主语、宾语或表语： 1.作主语 The way you are doing it is completely crazy.你这个干法简直发疯。 The way she puts on that accent really irritates me. 她故意操那种口音的样子实在令我恼火。The way she behaved towards him was utterly ruthless. 她对待他真是无情至极。 Words are important, but the way a person stands, folds his or her arms or moves his or her hands can also give us information about his or her feelings. 言语固然重要,但人的站姿,抱臂的方式和手势也回告诉我们他(她)的情感。 2.作宾语 I hate the way she stared at me.我讨厌她盯我看的样子。 We like the way that her hair hangs down.我们喜欢她的头发笔直地垂下来。 You could tell she was foreign by the way she was dressed. 从她的穿著就可以看出她是外国人。 She could not hide her amusement at the way he was dancing. 她见他跳舞的姿势，忍俊不禁。 3.作表语 This is the way the accident happened.这就是事故如何发生的。 Believe it or not, that's the way it is. 信不信由你, 反正事情就是这样。 That's the way I look at it, too. 我也是这么想。 That was the way minority nationalities were treated in old China. 那就是少数民族在旧中
(完整版)the的用法
定冠词the的用法： 定冠词the与指示代词this ,that同源,有“那(这)个”的意思,但较弱,可以和一个名词连用,来表示某个或某些特定的人或东西. (1)特指双方都明白的人或物 Take the medicine.把药吃了. (2)上文提到过的人或事 He bought a house.他买了幢房子. I've been to the house.我去过那幢房子. (3)指世界上独一无二的事物 the sun ,the sky ,the moon, the earth (4)单数名词连用表示一类事物 the dollar 美元 the fox 狐狸 或与形容词或分词连用,表示一类人 the rich 富人 the living 生者 (5)用在序数词和形容词最高级,及形容词等前面 Where do you live?你住在哪? I live on the second floor.我住在二楼. That's the very thing I've been looking for.那正是我要找的东西. (6)与复数名词连用,指整个群体 They are the teachers of this school.(指全体教师) They are teachers of this school.(指部分教师) (7)表示所有,相当于物主代词,用在表示身体部位的名词前 She caught me by the arm.她抓住了我的手臂. (8)用在某些有普通名词构成的国家名称,机关团体,阶级等专有名词前 the People's Republic of China 中华人民共和国 the United States 美国 (9)用在表示乐器的名词前 She plays the piano.她会弹钢琴. (10)用在姓氏的复数名词之前,表示一家人 the Greens 格林一家人(或格林夫妇) (11)用在惯用语中 in the day, in the morning... the day before yesterday, the next morning... in the sky... in the dark... in the end... on the whole, by the way...
“the way+从句”结构的意义及用法
“tｈｅwａｙ+从句”结构的意义及用法 首先让我们来看下面这个句子: Ｒead the foｌloｗｉnｇpassagｅａnd talkａbout ｉt wi ｔh your classmaｔes．Try tｏｔeｌl whaｔyｏu thiｎk ｏf Tom aｎd ｏｆｔhe ｗay the chiｌｄrenｔrｅated ｈim. 在这个句子中，ｔhe waｙ是先行词,后面是省略了关系副词that或in whｉch的定语从句。 下面我们将叙述“the ｗaｙ+从句”结构的用法。 1.tｈe wａy之后，引导定语从句的关系词是tｈat而不是hoｗ,因此，<<现代英语惯用法词典＞＞中所给出的下面两个句子是错误的：Ｔhｉs is ｔｈeｗayｈowｉtｈａppened. This is the way how he ａlwａｙs treats me. 2．在正式语体中,thaｔ可被in which所代替;在非正式语体中，ｔhat则往往省略。由此我们得到theｗay后接定语从句时的三种模式：1) tｈe ｗaｙ＋ｔhａt-从句２）the way +ｉn whiｃh－从句3) the ｗay +从句 例如：Ｔｈe way(in whiｃh ，thａt) ｔhｅｓｅｃomｒade ｓloｏｋａｔｐrobｌems is wrong．这些同志看问题的方法
不对。 Ｔｈｅｗａy(that ,ｉn ｗhiｃh)yoｕ’ｒe doinｇit is comple ｔeｌy crａzy.你这么个干法,简直发疯。 Wｅａdmiｒｅd him for thｅｗay ｉｎｗhｉch he fａｃeｓdiｆficultieｓ． Waｌlａｃe ａｎd Ｄarwiｎｇreed ｏn the way ｉｎwhi ｃh ｄｉfｆｅrｅnt forms ｏf life had ｂegｕn.华莱士和达尔文对不同类型的生物是如何起源的持相同的观点。 Thｉs is ｔｈe ｗaｙ（tｈａｔ) hｅdｉd it. I lｉkeｄｔhe waｙ(ｔhat) ｓｈeｏｒganized ｔhe ｍeetｉng． 3.theｗay(tｈat)有时可以与hｏw(作“如何”解）通用。例如： That’s tｈe ｗaｙ(tｈaｔ) shｅspoke. = Tｈat’s how shｅspoke.
way 用法
表示“方式”、“方法”，注意以下用法： 1.表示用某种方法或按某种方式，通常用介词in(此介词有时可省略)。如： Do it (in) your own way. 按你自己的方法做吧。 Please do not talk (in) that way. 请不要那样说。 2.表示做某事的方式或方法，其后可接不定式或of doing sth。 如： It’s the best way of studying [to study] English. 这是学习英语的最好方法。 There are different ways to do [of doing] it. 做这事有不同的办法。 3.其后通常可直接跟一个定语从句(不用任何引导词)，也可跟由that 或in which 引导的定语从句，但是其后的从句不能由how 来引导。如： 我不喜欢他说话的态度。 正：I don’t like the way he spoke. 正：I don’t like the way that he spoke. 正：I don’t like the way in which he spoke. 误：I don’t like the way how he spoke. 4.注意以下各句the way 的用法： That’s the way (=how) he spoke. 那就是他说话的方式。 Nobody else loves you the way(=as) I do. 没有人像我这样爱你。 The way (=According as) you are studying now, you won’tmake much progress. 根据你现在学习情况来看，你不会有多大的进步。 2007年陕西省高考英语中有这样一道单项填空题： ——I think he is taking an active part insocial work. ——I agree with you_____. A、in a way B、on the way C、by the way D、in the way 此题答案选A。要想弄清为什么选A，而不选其他几项，则要弄清选项中含way的四个短语的不同意义和用法，下面我们就对此作一归纳和小结。 一、in a way的用法 表示：在一定程度上，从某方面说。如： In a way he was right.在某种程度上他是对的。注：in a way也可说成in one way。 二、on the way的用法 1、表示：即将来(去)，就要来(去)。如： Spring is on the way.春天快到了。 I'd better be on my way soon.我最好还是快点儿走。 Radio forecasts said a sixth-grade wind was on the way.无线电预报说将有六级大风。 2、表示：在路上，在行进中。如： He stopped for breakfast on the way.他中途停下吃早点。 We had some good laughs on the way.我们在路上好好笑了一阵子。 3、表示：(婴儿)尚未出生。如： She has two children with another one on the way.她有两个孩子，现在还怀着一个。 She's got five children，and another one is on the way.她已经有5个孩子了，另一个又快生了。 三、by the way的用法
The way的用法及其含义(一)
The way的用法及其含义（一） 有这样一个句子：In 1770 the room was completed the way she wanted. 1770年，这间琥珀屋按照她的要求完成了。 the way在句中的语法作用是什么？其意义如何？在阅读时，学生经常会碰到一些含有the way 的句子，如：No one knows the way he invented the machine. He did not do the experiment the way his teacher told him.等等。他们对the way 的用法和含义比较模糊。在这几个句子中，the way之后的部分都是定语从句。第一句的意思是，“没人知道他是怎样发明这台机器的。”the way的意思相当于how；第二句的意思是，“他没有按照老师说的那样做实验。”the way 的意思相当于as。在In 1770 the room was completed the way she wanted.这句话中，the way也是as的含义。随着现代英语的发展，the way的用法已越来越普遍了。下面，我们从the way的语法作用和意义等方面做一考查和分析： 一、the way作先行词，后接定语从句 以下3种表达都是正确的。例如：“我喜欢她笑的样子。” 1. the way+ in which +从句 I like the way in which she smiles. 2. the way+ that +从句 I like the way that she smiles. 3. the way + 从句(省略了in which或that) I like the way she smiles. 又如：“火灾如何发生的，有好几种说法。” 1. There were several theories about the way in which the fire started. 2. There were several theories about the way that the fire started.
way 的用法
way 的用法 【语境展示】 1. Now I’ll show you how to do the experiment in a different way. 下面我来演示如何用一种不同的方法做这个实验。 2. The teacher had a strange way to make his classes lively and interesting. 这位老师有种奇怪的办法让他的课生动有趣。 3. Can you tell me the best way of working out this problem? 你能告诉我算出这道题的最好方法吗？ 4. I don’t know the way (that / in which) he helped her out. 我不知道他用什么方法帮助她摆脱困境的。 5. The way (that / which) he talked about to solve the problem was difficult to understand. 他所谈到的解决这个问题的方法难以理解。 6. I don’t like the way that / which is being widely used for saving water. 我不喜欢这种正在被广泛使用的节水方法。 7. They did not do it the way we do now. 他们以前的做法和我们现在不一样。 【归纳总结】 ●way作“方法，方式”讲时，如表示“以……方式”，前面常加介词in。如例1； ●way作“方法，方式”讲时，其后可接不定式to do sth.，也可接of doing sth. 作定语，表示做某事的方法。如例2，例3；
the-way-的用法讲解学习
t h e-w a y-的用法
The way 的用法 "the way+从句"结构在英语教科书中出现的频率较高, the way 是先行词, 其后是定语从句.它有三种表达形式:1) the way+that 2)the way+ in which 3)the way + 从句(省略了that或in which),在通常情况下, 用in which 引导的定语从句最为正式,用that的次之,而省略了关系代词that 或 in which 的, 反而显得更自然,最为常用.如下面三句话所示,其意义相同. I like the way in which he talks. I like the way that he talks. I like the way he talks. 一.在当代美国英语中,the way用作为副词的对格,"the way+从句"实际上相当于一个状语从句来修饰全句. the way=as 1)I'm talking to you just the way I'd talk to a boy of my own. 我和你说话就象和自己孩子说话一样. 2)He did not do it the way his friend did. 他没有象他朋友那样去做此事. 3)Most fruits are naturally sweet and we can eat them just the way they are ----all we have to do is clean or peel them . 大部分水果天然甜润,可以直接食用,我们只需要把他们清洗一下或去皮.
way的用法总结大全
way的用法总结大全 way的用法你知道多少，今天给大家带来way的用法，希望能够帮助到大家，下面就和大家分享，来欣赏一下吧。 way的用法总结大全 way的意思 n. 道路,方法,方向,某方面 adv. 远远地，大大地 way用法 way可以用作名词 way的基本意思是“路,道,街,径”,一般用来指具体的“路,道路”,也可指通向某地的“方向”“路线”或做某事所采用的手段,即“方式,方法”。way还可指“习俗,作风”“距离”“附近,周围”“某方面”等。 way作“方法,方式,手段”解时,前面常加介词in。如果way前有this, that等限定词,介词可省略,但如果放在句首,介词则不可省略。
way作“方式,方法”解时,其后可接of v -ing或to- v 作定语,也可接定语从句,引导从句的关系代词或关系副词常可省略。 way用作名词的用法例句 I am on my way to the grocery store.我正在去杂货店的路上。 We lost the way in the dark.我们在黑夜中迷路了。 He asked me the way to London.他问我去伦敦的路。 way可以用作副词 way用作副词时意思是“远远地,大大地”,通常指在程度或距离上有一定的差距。 way back表示“很久以前”。 way用作副词的用法例句 It seems like Im always way too busy with work.我工作总是太忙了。 His ideas were way ahead of his time.他的思想远远超越了他那个时代。 She finished the race way ahead of the other runners.她第一个跑到终点,远远领先于其他选手。 way用法例句
the_way的用法大全教案资料
t h e_w a y的用法大全
The way 在the way+从句中, the way 是先行词, 其后是定语从句.它有三种表达形式:1) the way+that 2)the way+ in which 3)the way + 从句(省略了that或in which),在通常情况下, 用in which 引导的定语从句最为正式,用that的次之,而省略了关系代词that 或 in which 的, 反而显得更自然,最为常用.如下面三句话所示,其意义相同. I like the way in which he talks. I like the way that he talks. I like the way he talks. 如果怕弄混淆，下面的可以不看了 另外，在当代美国英语中,the way用作为副词的对格,"the way+从句"实际上相当于一个状语从句来修饰全句. the way=as 1)I'm talking to you just the way I'd talk to a boy of my own. 我和你说话就象和自己孩子说话一样. 2)He did not do it the way his friend did. 他没有象他朋友那样去做此事. 3)Most fruits are naturally sweet and we can eat them just the way they are ----all we have to do is clean or peel them . 大部分水果天然甜润,可以直接食用,我们只需要把他们清洗一下或去皮. the way=according to the way/judging from the way 4)The way you answer the qquestions, you must be an excellent student. 从你回答就知道,你是一个优秀的学生. 5)The way most people look at you, you'd think a trashman was a monster. 从大多数人看你的目光中,你就知道垃圾工在他们眼里是怪物. the way=how/how much 6)I know where you are from by the way you pronounce my name. 从你叫我名字的音调中,我知道你哪里人. 7)No one can imaine the way he misses her. 人们很想想象他是多么想念她. the way=because 8) No wonder that girls looks down upon me, the way you encourage her. 难怪那姑娘看不起我, 原来是你怂恿的
the way 的用法
The way 的用法 "the way+从句"结构在英语教科书中出现的频率较高, the way 是先行词, 其后是定语从句.它有三种表达形式:1) the way+that 2)the way+ in which 3)the way + 从句(省略了that或in which),在通常情况下, 用in which 引导的定语从句最为正式,用that的次之,而省略了关系代词that 或in which 的, 反而显得更自然,最为常用.如下面三句话所示,其意义相同. I like the way in which he talks. I like the way that he talks. I like the way he talks. 一.在当代美国英语中,the way用作为副词的对格,"the way+从句"实际上相当于一个状语从句来修饰全句. the way=as 1)I'm talking to you just the way I'd talk to a boy of my own. 我和你说话就象和自己孩子说话一样. 2)He did not do it the way his friend did. 他没有象他朋友那样去做此事. 3)Most fruits are naturally sweet and we can eat them just the way they are ----all we have to do is clean or peel them . 大部分水果天然甜润,可以直接食用,我们只需要把他们清洗一下或去皮.
the way=according to the way/judging from the way 4)The way you answer the qquestions, you must be an excellent student. 从你回答就知道,你是一个优秀的学生. 5)The way most people look at you, you'd think a trashman was a monster. 从大多数人看你的目光中,你就知道垃圾工在他们眼里是怪物. the way=how/how much 6)I know where you are from by the way you pronounce my name. 从你叫我名字的音调中,我知道你哪里人. 7)No one can imaine the way he misses her. 人们很想想象他是多么想念她. the way=because 8) No wonder that girls looks down upon me, the way you encourage her. 难怪那姑娘看不起我, 原来是你怂恿的 the way =while/when(表示对比) 9)From that day on, they walked into the classroom carrying defeat on their shoulders the way other students carried textbooks under their arms. 从那天起,其他同学是夹着书本来上课,而他们却带着"失败"的思想负担来上课.
The way的用法及其含义(三)
The way的用法及其含义（三） 三、the way的语义 1. the way=as（像） Please do it the way I’ve told you.请按照我告诉你的那样做。 I'm talking to you just the way I'd talk to a boy of my own.我和你说话就像和自己孩子说话一样。 Plant need water the way they need sun light. 植物需要水就像它们需要阳光一样。 2. the way=how（怎样，多么） No one can imagine the way he misses her.没人能够想象出他是多么想念她！ I want to find out the way a volcano has formed.我想弄清楚火山是怎样形成的。 He was filled with anger at the way he had been treated.他因遭受如此待遇而怒火满腔。That’s the way she speaks.她就是那样讲话的。 3. the way=according as （根据） The way you answer the questions, you must be an excellent student.从你回答问题来看，你一定是名优秀的学生。 The way most people look at you, you'd think a trash man was a monster.从大多数人看你的目光中,你就知道垃圾工在他们眼里是怪物。 The way I look at it, it’s not what you do that matters so much.依我看，重要的并不是你做什么。 I might have been his son the way he talked.根据他说话的样子，好像我是他的儿子一样。One would think these men owned the earth the way they behave.他们这样行动，人家竟会以为他们是地球的主人。
way的用法
一．Way：“方式”、“方法” 1.表示用某种方法或按某种方式 Do it (in) your own way. Please do not talk (in) that way. 2.表示做某事的方式或方法 It’s the best way of studying [to study] English.。 There are different ways to do [of doing] it. 3.其后通常可直接跟一个定语从句(不用任何引导词)，也可跟由that 或in which 引导的定语从句 正：I don’t like the way he spoke. I don’t like the way that he spoke. I don’t like the way in which he spoke.误：I don’t like the way how he spoke. 4. the way 的从句 That’s the way (=how) he spoke. I know where you are from by the way you pronounce my name. That was the way minority nationalities were treated in old China. Nobody else loves you the way(=as) I do. He did not do it the way his friend did. 二．固定搭配 1. In a/one way：In a way he was right. 2. In the way /get in one’s way I'm afraid your car is in the way， If you are not going to help，at least don't get in the way. You'll have to move－you're in my way. 3. in no way Theory can in no way be separated from practice. 4. On the way (to……) Let’s wait a few moments. He is on the way Spring is on the way. Radio forecasts said a sixth-grade wind was on the way. She has two children with another one on the way. 5. By the way By the way，do you know where Mary lives? 6. By way of Learn English by way of watching US TV series. 8. under way 1. Elbow one’s way He elbowed his way to the front of the queue. 2. shoulder one’s way 3. feel one‘s way 摸索着向前走；We couldn’t see anything in the cave, so we had to feel our way out 4. fight/force one’s way 突破。。。而前进The surrounded soldiers fought their way out. 5.. push/thrust one‘s way（在人群中）挤出一条路He pushed his way through the crowd. 6. wind one’s way 蜿蜒前进 7. lead the way 带路，领路；示范 8. lose one‘s way 迷失方向 9. clear the way 排除障碍，开路迷路 10. make one’s way 前进，行进The team slowly made their way through the jungle.
the way的用法大全
在the way+从句中, the way 是先行词, 其后是定语从句.它有三种表达形式:1) the way+that 2)the way+ in which 3)the way + 从句(省略了that或in which),在通常情况下, 用in which 引导的定语从句最为正式,用that的次之,而省略了关系代词that 或in which 的, 反而显得更自然,最为常用.如下面三句话所示,其意义相同. I like the way in which he talks. I like the way that he talks. I like the way he talks. 如果怕弄混淆，下面的可以不看了 另外，在当代美国英语中,the way用作为副词的对格,"the way+从句"实际上相当于一个状语从句来修饰全句. the way=as 1)I'm talking to you just the way I'd talk to a boy of my own. 我和你说话就象和自己孩子说话一样. 2)He did not do it the way his friend did. 他没有象他朋友那样去做此事. 3)Most fruits are naturally sweet and we can eat them just the way they are ----all we have to do is clean or peel them . 大部分水果天然甜润,可以直接食用,我们只需要把他们清洗一下或去皮. the way=according to the way/judging from the way 4)The way you answer the qquestions, you must be an excellent student. 从你回答就知道,你是一个优秀的学生. 5)The way most people look at you, you'd think a trashman was a monster. 从大多数人看你的目光中,你就知道垃圾工在他们眼里是怪物. the way=how/how much 6)I know where you are from by the way you pronounce my name. 从你叫我名字的音调中,我知道你哪里人. 7)No one can imaine the way he misses her. 人们很想想象他是多么想念她. the way=because 8) No wonder that girls looks down upon me, the way you encourage her. 难怪那姑娘看不起我, 原来是你怂恿的 the way =while/when(表示对比) 9)From that day on, they walked into the classroom carrying defeat on their shoulders the way other students carried textbooks under their arms.
“the-way+从句”结构的意义及用法知识讲解
“the way+从句”结构的意义及用法 首先让我们来看下面这个句子： Read the following passage and talk about it with your classmates. Try to tell what you think of Tom and of the way the children treated him. 在这个句子中，the way是先行词，后面是省略了关系副词that 或in which的定语从句。 下面我们将叙述“the way+从句”结构的用法。 1．the way之后，引导定语从句的关系词是that而不是how,因此，<<现代英语惯用法词典>>中所给出的下面两个句子是错误的：This is the way how it happened. This is the way how he always treats me. 2. 在正式语体中，that可被in which所代替；在非正式语体中，that则往往省略。由此我们得到the way后接定语从句时的三种模式：1) the way +that-从句2) the way +in which-从句3) the way +从句 例如：The way(in which ,that) these comrades look at problems is wrong.这些同志看问题的方法不对。
The way(that ,in which)you’re doing it is completely crazy.你这么个干法，简直发疯。 We admired him for the way in which he faces difficulties. Wallace and Darwin greed on the way in which different forms of life had begun.华莱士和达尔文对不同类型的生物是如何起源的持相同的观点。 This is the way (that) he did it. I liked the way (that) she organized the meeting. 3.the way(that)有时可以与how(作“如何”解)通用。例如： That’s the way (that) she spoke. = That’s how she spoke. I should like to know the way/how you learned to master the fundamental technique within so short a time. 4．the way的其它用法：以上我们讲的都是用作先行词的the way，下面我们将叙述它的一些用法。
定冠词the的12种用法
定冠词the的12种用法 定冠词the 的12 种用法，全知道?快来一起学习吧。下面就和大家分享，来欣赏一下吧。 定冠词the 的12 种用法，全知道? 定冠词the用在各种名词前面，目的是对这个名词做个记号，表示它的特指属性。所以在词汇表中，定冠词the 的词义是“这个，那个，这些，那些”，可见，the 即可以放在可数名词前，也可以修饰不可数名词，the 后面的名词可以是单数，也可以是复数。 定冠词的基本用法： (1) 表示对某人、某物进行特指，所谓的特指就是“不是别的，就是那个!”如： The girl with a red cap is Susan. 戴了个红帽子的女孩是苏珊。 (2) 一旦用到the，表示谈话的俩人都知道说的谁、说的啥。如：
The dog is sick. 狗狗病了。(双方都知道是哪一只狗) (3) 前面提到过的，后文又提到。如： There is a cat in the tree.Thecat is black. 树上有一只猫，猫是黑色的。 (4) 表示世界上唯一的事物。如： The Great Wall is a wonder.万里长城是个奇迹。(5) 方位名词前。如： thenorth of the Yangtze River 长江以北地区 (6) 在序数词和形容词最高级的前面。如： Who is the first?谁第一个? Sam is the tallest.山姆最高。 但是不能认为，最高级前必须加the，如： My best friend. 我最好的朋友。 (7) 在乐器前。如： play the flute 吹笛子
Way的用法
Way用法 A:I think you should phone Jenny and say sorry to her. B:_______. It was her fault. A. No way B. Not possible C. No chance D. Not at all 说明：正确答案是A. No way，意思是“别想！没门！决不！” 我认为你应该打电话给珍妮并向她道歉。 没门！这是她的错。 再看两个关于no way的例句： （1）Give up our tea break? NO way! 让我们放弃喝茶的休息时间？没门儿！ （2）No way will I go on working for that boss. 我决不再给那个老板干了。 way一词含义丰富，由它构成的短语用法也很灵活。为了便于同学们掌握和用好它，现结合实例将其用法归纳如下： 一、way的含义 1. 路线
He asked me the way to London. 他问我去伦敦的路。 We had to pick our way along the muddy track. 我们不得不在泥泞的小道上择路而行。 2. （沿某）方向 Look this way, please. 请往这边看。 Kindly step this way, ladies and gentlemen. 女士们、先生们，请这边走。 Look both ways before crossing the road. 过马路前向两边看一看。 Make sure that the sign is right way up. 一定要把符号的上下弄对。 3. 道、路、街，常用以构成复合词 a highway（公路），a waterway（水路），a railway（铁路），wayside（路边）
way与time的特殊用法
way/time的特殊用法 1、当先行词是way意思为”方式.方法”的时候,引导定语从句的关系词有下列3种形式： Way在从句中做宾语 The way that / which he explained to us is quite simple. Way在从句中做状语 The way t hat /in which he explained the sentence to us is quite simple. 2、当先行词是time时,若time表示次数时,应用关系代词that引导定语从句,that可以省略; 若time表示”一段时间”讲时,应用关系副词when或介词at/during + which引导定语从句 1.Is this factory _______ we visited last year? 2.Is this the factory-------we visited last year? A. where B in which C the one D which 3. This is the last time _________ I shall give you a lesson. A. when B that C which D in which 4.I don’t like the way ________ you laugh at her. A . that B on which C which D as 5.He didn’t understand the wa y ________ I worked out the problem. A which B in which C where D what 6.I could hardly remember how many times----I’ve failed. A that B which C in which D when 7.This is the second time--------the president has visited the country. A which B where C that D in which 8.This was at a time------there were no televisions, no computers or radios. A what B when C which D that