1996ApJ...465...79S THE © lent the (1983). its galaxy galaxies galaxies. Either the that remain was stellar scenarios Creek gratuitous Advanced North Charles Technology, Tyler 225, Michigan, MD21218. 1996. Understanding NGC 2 4 1 3 8 5 9 6 7 10 linkage AsTROPHYSICAL Based Pasadena, Department Department Mount Jet Department Space Lowell Department major based to Local Division the The Mall, Post Charter Street, Propulsion systems There the American the mergers way, (Centaurus clusters giant RoBERTO mag; turn-up possibly NGC affected on CHRISTOPHER]. Subject tion halo, stellar 2455 5128 ± is Studies, on Telescope Office, Tempe, Observatory, have Pasadena, We The upon Stromlo ripe disk to 0.2 stellar through proving observations © Group. the of Street, Baltimore, CA Hayward, of the Astronomical the Geological is is the halo the however, branch of American of Astronomy, of of for present ACT 5128 population (Toomre been 91109. presence planetary Australian problems AZ (Quillen, JOURNAL, the a headings: classified Laboratory, resolution as Astronomy, in and Physics by Atmospheric Science similar lenticular class characteristics Madison, population SoRIA, neutral the DETECTION NGC and 85287. CA 2611, ground the the its More asymptotic 1. the A), explored Mars to MD Ann in 91125. with Society. nature (RGB) J. a and INTRODUCTION of dominant Siding luminosity Institute, Australia. be origin and the 465:79-90, completeness BURRows, 2 based National & 21218. color-magnitude the Arbor, 5128 of JEFF Graham, to Hill KARL WI NGC nebulae JEREMY the "SO hydrogen of Planetary galaxies: galaxies: 4800 of Johns All Astronomical of recent University for less Toomre Astronomy, number an the and 53706. NASA/ESA Road, rights astrophysics. dwarf of elliptical stars of the Spring by HESTER, (i.e., pee"; theories MI of intermediate-age Oak on 3700 than R. elliptical giant 5128 the halo the Hopkins value Oceanic University, reserved. is Malin, of dwarf 1996 spheroid 48109. R. these Flagstaff, OF luminosity insights 5 Sciences, function WFPC2 & STAPELFELDT, a is through Grove San elliptical distances STEFANOCASERTAN0, stellar remnant of of Observatories, 1972; the MoULD, its distance July exhibits compared Frogel ~ Arizona branch 8 Printed level found galaxies Wisconsin-Madison, Hubble THE of Martin these elliptical 10% linkage pressure-supported JoHN University, Sciences, Quinn, stellar Drive, of 1 galaxies the Received AZ California Private diagram Schweizer content- Baade's in (Graham have of at the its Society images U.S.A. 2 Space 86001. stars TIP 1993). origin Drive, galaxy of in in State function and of stars, a G. I~ our ALAN Mail striking was Milky to broad & the halo the population University the M31 with 7 galaxies Bag, stellar 3.6 1995 Institute HoESSEL, suggested 3400 Telescope. is redshifts- JoHN constrains University, OF Institute 24.1 elliptical Graham sample, Baltimore, of Stop surmise of equiva­ Merger extending through ± total. one M. NGC Weston October 1979); 1994). the more and these • North stars: Way and 0.2 range THE ABSTRACT and ± population 179- T. WATSON, 475 Provided 6 of of of of of of 0.1 loci JoHNT. 2 Mpc), The higher TRAUGER, strongly on 185; 30; than JoN Hertzsprung-Russell 79 of RED mag; the V-band of galaxies: the accepted up color levels major the provides four couleurs examined close illustrated galaxy Its Bicknell, We tized probe NGC system. south full only exposures), low-resolution Space performed (1995b) al. 1983, 1986). Bias A. the were 1300, the in the intermediate-age 3 10,000 than surface to CLARKE, JoHNS. The Eight this ( GIANT proximity agreement HoLTZMAN, by suggests (1994) galaxy ~ description begin 7 high-resolution tip red I= subtraction, through 1996 distribution systems of relation and Sky and 5 AND then of 1984) 5128 active the that Telescope resolution yields distance the individual Until stars chemical Gyr) and of CCD giant the 22.6 1993). & January brightness a Survey). 1300 4 stellar from I-band 2. the and GALLAGHER JAMEs in (Schiminovich according the NASA laboratory DAVID observed averaged Dopita were and BRANCH center of a and galactic OBSERVATIONS in a is makes now Figure mag the to that with study mean branch images 9 wide Stetson s distance RGB the of indicators the suggested 5 the that exposures). the PAUL diagram population flat-fielding, enrichment. obtained A. to (HST) and F555W stellar (NGC at WFPC2 filters. the We CRisP, could (for of previous instrument 1993). ground Astrophysics halo field fluctuations it WESTPHAL planetary by the other value constant nucleus, seen 1 to in is the Local in sensitivity a of in find (1995); A. (image III, for V-I> IN examining the useful modulus signalled NGC halo population provide 5128)- 7 chips a of be galaxy; six order The et filter in (see, As ScoWEN, by RicHARD 3 four of on can 160" gas/jet a prescriptions NGC (Mould, the Group Figure GILDA al. the resolved of determinations well-studied AND stellar Centaurus a and the [Fe/H] of the 1995 testing position I taken e.g., superposed 10 camera 185. this be factor (1100, handbook 1993). 2) galaxy through to dwarf x magnitude, of technique. the M31 a (m- luminosity found cosmic-ray two by 5128 and PHOTOMETRY 160" interaction a 8 Hui E. spheroids 1 WFPC2 nearest obtain unique May E. Data Like population in Kristian, halo position shows from ground into an of > The BALLESTER, 1100, series ellipticals GRIFFITHS, (Mould Mbot M) 1 NGC the halo the chip et of field 5 -0.9 in A, F814W of observed 30 the globular al. closer field 0 System individual on galaxy's the (Burrows the both large a it the Holtzman opportunity = 500, ~ with on based of albeit and in 1993; func­ for have is removal 5128 M31 of the single 27.8 & dex, (Sutherland, STSci red -5 geometry some four & the the that the our of Trauger than previously early-type early-type and Da 6 (600, 4 galaxy. the WFPC2: been Kristian de activity nearest halo Hubble images field is Costa image 9 1994). M87. stars. 500 Digi­ Vau­ three et were 600, in kpc the al. to of of et A is a s 1996ApJ...465...79S filter (divided filter. detected correction ing 80 determined 40" the the tion ALLFRAME rithm point-spread program A Stetson's Wide x F555W (the preliminary ::GG SGG JQQ IGG was A in 40"). section in into pixel DAOPHOT; © Field compiled DAOMASTER to only We with American convention). image the four function area (Stetson . ... then of Camera one . FIG. .. pixel list . the the '" . chips . was . . vignetted using color, did of 1.-Position ... resulting .r•. . reduction area their stars (pst) rescaled 1991a, .. has not Astronomical and lOll the as accounting allowed instrumental been detected to well match the rescaled automatic F814W b, of to each packages our four as printed 1994, the stars field their us in frames star. for image average to 1995) in each to star-finding whose in magnitudes geometric Society the 1000 ALLST position The Figure halo from discard and chip that one, s) position ofNGC matching applied chip for AR for fitted follow- 2 • distor- in SORIA (size: algo- stars were each each Provided lCIII and 2 the 5128;image in in a a ET (we (relatively) for (Planetary ue a duced in compare problems point-spread aperture F814W therefore, with were 3273 3, from by AL. chip and all estimated retained the in the those four 4 1 image chip STSci linear radius (Wide made NASA explained the we Camera). chips, isolated . obtained 3, Digitized decided (563 function-fitting values • to . an correction and our = Field within for Astrophysics 0':5, error of calibration in 3827 bright Unfortunately, the them Sky of with to Holtzman Camera) . corresponding .. . 0':04. sake the Survey of adopt in for detected aperture stars a chip magnitudes of Eventually, the few ; algorithm size: rather Stetson's and consistency. et in 4). charge Data tenths 20' al. in the each We to photometry, chip to (1995a): x uncertain 11 lack 20' •• then 5 System (1995) transfer estimated some of chip in pixels 1, pixels We a 3422 of ALLFRAME chose stars magnitude); in 11,000 bright zero for also in in efficiency in using order Vol. chips located the several by chip chip points intra- stars stars 465 PC the an to 2, 2, 1 1996ApJ...465...79S No. (see (1995a): in been mented and the while required where metric relation uncertain I v. Filter { .... FIG. Finally, u V . the standard I= .... bias- 1, the Although also .. = stars 2.-lmage Bv 1996 SOOth for system v i by using and 0.967 between F555W values 1.861 © + + Burrows data = VALUE + in the 2.5log 2.5 American cosmic-ray PC1 0/- -0.052, magnitudes this ± ± the row with the conversion log 0 0 to of of O.o2 . . OF 017 018 is is first DIFFERENT ALLFRAME a this the A coefficients (texp)- roughly were THE a (texp)- 40" 1994) from - standard for illumination Cv subtracted. 0.958 row were 1.823 standard ADoPTED x this 40" Astronomical adjusted the . = WF2 V TABLE A- In ± ± A- FILTERS equivalent unknown. from field 0.027, and 0.014 0 different correction, . detail, 009 ZERO tabulated BiV Bv(V- in left level. I: psf Cousins 1 the the AND B to 0.950 unchanged. 1.842 POINT magnitudes 1 -I)- TIP We halo we = WFPC2 be CmPS filters to it WF3 I)- regard -0.063, ± ± is 0.04 of used V, in A OF colors 0 0.009 Society unclear CiV . NGC FOR 009 Cv(V- and Holtzman and our mag RED the THE 11 flight v 5128 -I) F814W to 0.973 1.870 maguitudes C was chips whether and 1 following I) brighter, = WF4 ' 2 • taken GIANT 2 photo­ ± ± imple­ 0.025, i, Provided et 0 0.013 have . and 011 it with (1) al. as is I WF2 BRANCH factor mined metric nique mate powerful plot photometric approximate all filter color-magnitude divided then minus random reran rescaling been by First, tudes 1995a). of by The Figures the the ALLFRAME the lines compared (z listed WFPC2, the all as to (different the fake by offset . of ADDST p IN by but . NASA the explained tool a true in = ALLFRAME term factor= adding 3 in stars four, 0':5 NGC a 21.724 both star-finding and ( = errors: through 50% for Table priori error); required the AR for + aperture could diagrams estimating Astrophysics initially, 4 color-magnitudes are completeness 25), 5128 "artificial" display for 2.5 below each magnitude the known 3. task we 1; therefore, not minus log V; be infrared A COMPLETENESS found with to algorithms chip is radius of recovered, z.p. in as reliable 4 of the correct position the the the DAOPHOT this explained some but (all the filter = that of (I, stars sum completeness we levels zero 20.840 (of Data value section, each ~0.75 F814W; V-I) pixel (they the the used 10,000 diagrams on and of order and point in (see instrumental added estimates DAOPHOT the given for in System the brightness, and mag tend and values our this the Figs. we stars proved Holtzman new I), (z ~0.1), standard image . p.) evaluated of the for as signalling allowed star frames, to minus 9 in images. our for input. and calculated had underesti­ 7e- (V, has our as minus to a magni­ sample photo­ a already deter­ 10). V-I) gain), given et tech­ us field. be been with gain Not We the the we al. 81 to a a 1996ApJ...465...79S 82 values magnitudes studied in 22.5 I I= and added and verify same all DAOMASTER) magnitude, the ADDSTAR respective ratio same distribution easier allowed original to when the magnitude; be the = FIG. The a detect the both stars photometric 27.5 22.5 in the PSF little ADDSTAR level AGB will 23 24 25 26 mag 27 about than of Astronomical diagram give our stars 1 the sample algorithm the mag + + + in observed time 0 TIP most significant the above as (V, spent a was OF function V-I) Society the used is RED on correspond­ plane RGB to the of determine GIANT V-I, for contri­ RGB; tip, • the Provided for as same BRANCH V-I stars we 3 account our gives know taken magnitude mag. Armandroff E(B- studied adopted a abundances 27.72 this 5128 ' . as common and The ~:·'.:. by 2 shall in value field, and We Fig. mag the 4 V) :- from the E(V .. solid IN may for galactic argue here 3. relation tentatively the reddenings NGC NGC NGC NGC NGC NGC is The -I)= NASA scale using but diagram NGC all (see Burstein ·-: (1990). GALACTIC simply globular in lines are photometric in .. of FOR 7078 6752 6397 7089 104 1851 agreement we with Table Cluster globular § them. the 0.16 of those A 5128 (47 5.2: ...... Astrophysics (M2) (MIS) 3 superimposed The CoMPARISON be adopt Dean, estimate are and results GLOBULAR Tuc) the & clusters; ± some 2). spurious ...... found reddening error ...... the Heiles 0.02 NGC TABLE ..... the In clusters a Warren, with .. of discussed distance order giant has . . . . . distance WITH photometric CLUSTERS mag for in the 5128 (1984), been because 2 both [Fe/H] Table -1.58 -1.91 -2.17 -0.71 -1.29 -1.54 the points on to spanning for branch NGC Data 4 & determined RGB and modulus place latter, moduli the the NGC in ADoPTED Cousins using IX 5128 of plotted Hui System A stars, distance MI,TRGB (1, loci -4.039 -4.021 -3.948 -4.035 -3.765 -4.095 the those of 1 the errors 5128 various = as of V-I) the et Da (m crowding of before. (1978); 0.22 parameters both we in al. curves - E(V- has Costa six Figures need derived cannot (1993); M) ± color­ metal NGC well­ been 0.02 0 this 83 on 1)/ to of = & 1996ApJ...465...79S from clusters; inferred mined § 84 adopted inferred is in From two will roughly stars because abundances Green, galaxy giant DA90, Da relation In need function quantitative the nosity photometric simply by which steepest found of choose which with photometric first The in Freedman only fact given metric tion results. ± not branch similar function Five-point 5.1) nonlinear. Another The the 0.12 12 order the our Costa bias position present (independent) be The derivative solid derivative the are the only is a globular branch correction half-weight; tip to function inspection edge by in RGB Demarque, the the or discussed discontinuity. the case, mag we consistent bins from computer from the its ascent DA90 or planetary to in modulus and redder; the redder; is stars & Lee, a eye, comparing in line RGB to fainter (1995), greater data make first smoothing (m- adopted I other © cluster relevant same depends Armandroff equal the for of approach, error. smaller tip errors we associate determine a magnitude the giant loci American but with clusters in with in tip Freedman, comparison the in (LF). of stellar 5. derivative the luminosity than know can M) in than the cool words, surface Figure luminosity distance the techniques. and of the for with the LUMINOSITY to & nebulae branches A three-point simulation in discontinuity of tend § V-I 0 the 5.1. tip; relation specified It than an detection comprehensive mostly King population. be or those piece 6. = Figure LF). stars. the distant stars the LF tip Sakai, the was is that is one first the IrRGB- For the less absolute 1990, collected: hence, The indicator depends to the the 6 possible brightness > luminosity 0.1 is [ of of show The tip 1987) (Their luminosity & Astronomical displays M has can distance applied can of smear is AI= tip and here. 1.5 of less a upon shown than metallicity between distance RGB as galaxies the Madore, ~> 3 mag of Madore the hereafter a given using of smoothing They uncertainty (V- of that be mag differentiate information a metal-rich the FUNCTION the it last reliable This and luminosities ( the in provided the -3.98)- 0.22 RGB in RGBs very the maximum magnitude [Fe/H] out the expressed Tip appears in in for the to simply TRGB distance in the I) derived analysis RGB points some is luminosity, fluctuation metallicity, edge have artificial of like color 0 the function of RGB ± our due [Fe/H] the size Figure the & ] (1993b), little luminosity DA90). in distribution, the LF metal-poor distance 0.02 in stars). NGC plane Freedman to soften LF NGC a produced cases with = been luminosity edge; NGC case are in of in NGC AI. in little and from Society the of that RGB with the upon of -0.7 > modulus by that (the mag, the owing the the MI These the 8 predicted LFs 12 and NGC -0.7 effects the this 5128 the derived considered, to Madore 5128, luminosity metallicity we at (solid technique. the metal-rich easier; in "boxcar" From 5128 the 5128 indicator the with detection bins = stars globular tips point function estimate luminosity dex least age point can the method and effects a the can cannot similar simple (1996). -3.98 which of deter­ to SORIA other lumi­ 5128; more large func­ • line). are to of bolo­ and into (see one (see giant (see has the the for the the we by (2) be Provided be of at & do be in a ET line) mag, been gives ness planetary (Hui to of detected detected as ± ± z AL. z FIG. The before. 600 FIG. 400 the 200 0.14 0.1 the 60 40 by and considered. et fluctuation in a total number, 6.-I 7.-I mag result mag, in NGC al. the galaxy The agreement in true PC1; 1993). nebulae luminosity PC1 turn-up NASA luminosity 185 and is we only distance is (dashed obtained 20 (see This with technique, obtained I I stars in ~ 3.7 NGC c I with luminosity functions the Astrophysics but Fig. functions confirms ± 185 that line); redder LF I I modulus 1 0.2 I PC1 the 7): at by derived only is I for than Mpc. (m they modulus 22 = IrRGB has for considering the that stars function, 24.0 - V-I the are a (m- M) RGB The using ± redder better the = Data 0.1 = 0 RGB a determined 24.1 = stars small 1.5 most M) mag value the (m- 27.71 than 24 have resolution stars NGC 0 System ± in is only = surface likely fraction more NGC 0.1 V-I= 5128 been IrRGB 27.86 M) ± in mag: 0.10 0 evident. the NGC from considered, Vol. 5128 distance = bright­ 1.5 \ ± = (0':046 (1/20) 27.73 26 stars (solid mag 0.16 24.0 465 have this 5128 the 1996ApJ...465...79S pixel- (m the No.1, assume dent The on tance the (m- being first agreement assume in galaxies tudes the I= as tance the (solid maximum (m- As A FIG. a - the NGC LF ' , distance distance -o z 20.6 dashed derivative discontinuity relative line) techniques second M) a M) modulus found "' r'l ,.... 0 0 0 0 0 0 0 .... N 0 0 0 0 co 0 0 0 ~ 1 modulus LF of 8.-First 1996 test , at M)O,NGC this while 0 Ar,NGC 0 in appears ± and ,Nac the 5128 = 151 ofthe the LF's I with of © 0.1 line. " value at 27.76 NGC modulus modulus galaxy shift ' the tip it American 185 derivative ,, ofNGC I of RR 20 185 is is the 5128 (m- (Lee dwarf mag. = of I method I first I the to I 185; I = 0': I 11 to between ± M31 in 20.35 I = I I the I value I Lyrae I 1 24.02 to 0.16 be derivative. = be LF et 0.38 pixel- we M) derived the had elliptical RGB of 5128 (m- which + + Assuming AJTRGB al. more where can for 0 ± mag used the of ,Nac JTRGB,NGC ± Ar,Nac Astronomical mag /-band been stars 1993a; the 0.10 1 associate 20.30 is NGC 0.25 M)O,NGC I we in (3.6 reliable, from now to 5128 luminosity we 22 tip = galaxy Davidge mag the repeated and determined detect (Saha 185 mag; 3.65 ± chosen can Lee 185 of luminosity given = TIP Wide Field the (m- the 5128 0.2 for - adopt 185 27.8 the is NGC the ± 1995). relate tip this Ar,Nac the function Mpc). absolute & NGC OF shown - by 0.15 (1993) the M) by RGB of ± modulus discontinuity JTRGB,NGC Society Hoessel leads the for 0 0.3 with 185, Lee). same RED The the mag, = 24 185 5128 chips); function RGB in in in has NGC 24.3 mag. V for RGB NGC to indepen­ We true Figure (in analysis the • GIANT magni­ the will with which 1990): a found 185 • good if then The two and dis­ dis­ 5128 185 Provided we tip tip (3) be the in at 8 BRANCH (m from E(B- surement detected magnitudes tent resemblance to standard can may with I found eventually explain 1990). contamination giant density Figure mass material by bright particular, stellar stellar stars fore, analogy at compare above adding et Mould, tion tip the to but stars classes distance in magnitude metric the totic prominently 1990a). ± = These Although 2. 3. The 1. In 4. these 0.08 al. 20-25 - ALLFRAME. by in NGC it think 24 LMC LMC. distances, happen I They They We seen They Figures the M) with on giant giant surface (1993a) branch NGC seems V) the < distribution the with star With and of majority 13 mag constellation to We correction IN luminosities, between calculated & 0 seems results at effect 23 candle = modulus are detecting on stars the stars offour them of the at TRGB = and our I (Frogel 5128 are assigned at Thompson are NASA branch (m are 0.08 diagram, But by branch can NGC higher mag ~ 22 5128 and 27.63 I to I< the to the in 9 Tonry's most, suggests brightness stars: color-magnitude < images upper - in 23 with strained. discussed ALLFRAME. and but 5.2. us of that in simply < be foreground the infer with (Frogel in are of 22 RGB possible JTRGB number M) by south and by the 30% for magnitude mag I appear We Galactic their our ± overlapping 5128 (m- et luminosities: stars. in its the by mag. 10 to these < Stars nuclear (AGB) two Astrophysics ofNGC 18 0 a checking in consistent 0.2 asymptotic C-M plotting while as something Shapley about similar = al. some conclude 23.5 M31 magnitude the we and 5.8 (1995) large real tip. and these 1987); more + functions comer sample. the RGB (1993a), -12.64 - > its we and of -0.7 17.0(V-J) 3.33[(V- 23 24 25 26 for 27 color the stars can after diagram horizontal 1990) in the 5128, value Alternatively, useful are Astronomical 24.8 tip. I dn/d[Fe/H]. [Fe/H] intrinsic and adopt + RGB likely where = can in of correction 12.61(V- conservatively 24.2 of in The in that 0 the turn completeness I) ,- the Blue to be our [Fe/H] the our 0 one-half 0 TIP we cuts 3 ,- do dn/d[Fe/H] RGB be color (V, approximated relation -4.9[(V-J) require constrain data 3 relation defined Galactic case, we Stars . for 5 V-I) OF across We ] I) for 2 at have exceeds of 0 at Society the , mag , because M find - plane; RED completeness. the I mean 3 foreground is (V- disregarding 1 . ~ the same >50%. a 5 = - = the is below RGB sample valid 25 that 0 again, RGB -0.9 a ,- 1) GIANT by mag. metal­ values 0 of 3, range • rising 3 , over ] _ and (see we We i.e., Provided 2 the the stars; for (7) (6) 3 at in of . , 5 have BRANCH the V-I displayed thin, factor exceeding & luminosity the red niques work be Mv (1995). This (V-I) tions; the method, nebulae with in dwarf tip) The We 2. 1. 3. Mould by the 2 characteristic halo giant distance solid constrains ~ .. The We is the On , are the note ·. elliptical of for the -21. found range main ·. = ·~ IN a luminosity metallicity/luminosity . line 2 loci the values ' branches as extensively distance modulus 1; further notice 1988), NGC or -0.75, NASA that of NGC follows: ·. bright, ofthe marks The derived other more. conclusions Foreground the [Fe/H] -5 an AGB NGC Mould previously these 185 similarity the blue tip indication discussed rely relatively & the CONCLUSIONS stars of -0.6 the and halos by M31, Kristian TRGB the we Stars of the on red of determined for -4 observed 1993) of the Lee and of star have completeness luminosity RGB, the for can giant relation the NGC of it high of mag et in surface NGC formation their is AGB is (1986) also bright derive al. and luminous reliability Data 4 also Madore particularly branch metallicity 5128 (well (1993a). number stars; the halo been is using 5128 brightness in of using a guide from thick stars, System inferred above the corrections RR agreement field in is observed and galaxies of & the in of bright, line consequence similar Lyrae the values bluer striking. the AGB agreement in (DaCosta Freedman M31 planetary the is from fluctua­ M31. present red the TRGB in stars. RGB tech­ stars than with halo may with stars of 50% the the 87 If a 1996ApJ...465...79S 88 5128; z FIG. 600 the 12.-Mbol brightest © American luminosity AGB stars -5 extend -3 -4 -2 function FIG. Astronomical M(bol) up 11.-Color-magnitude for toMbol our 0 field ~ -5. in Society the halo diagram .. of SORIA • ... NGC . . . in Provided ·· .. the [Mbol• {V ET - probably stellar of tainties C-M viously NGC for contributing our completeness John the Carl our WFPC2 sponsored and -0.9 .. (V .. l)o AL. 4. We a -1) : by . 2 star tip analysis. field merger ,•·· Finally, suggestions. Grillmair diagram Graham 0 (considerably are ] the population; 185); of remain .. been plane count (causing Investigation · earlier ... the grateful by NASA to for found relatively their level NASA the RGB implies and calculations. add in the for the than large position stars This expertise falling Jay to less the Astrophysics in critical 3 are through larger evolutionary Daya a a in Frogel major photometric 5 Definition than high halo the mean research NGC below Gyr of reading We main than Rawson in about field 5128 contract metallicity epoch the for value ago, photometry thank the their sources was in the models. red Team 10% Data 50% of error) although 4 of M31. of and NAS?-1260. mean giant Gary the stimulating carried [Fe/H] star to limit values for Peter of System The and, manuscript the and formation DaCosta branch uncertainty JPL metallicity large 1 crowding pre-existing higher out above Stetson mag Neill have Vol. and remarks by uncer­ in below all, Reid than pre­ 465 was was and and the the for in in in a 1996ApJ...465...79S --. 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