J/ApJS/82/197 Mean UV Spectra of Stellar Groups (Fanelli+ 1992) ==================================================================== Spectral Synthesis in the Ultraviolet IV. A Library of Mean Stellar Groups Fanelli M.N., O'Connell R.W., Burstein D., Wu C.-C., =1992ApJS...82..197F A Database for Galaxy Evolution Modeling Leitherer C., et al. =1996PASP..108..996L ==================================================================== ADC_Keywords: Spectra, ultraviolet; Stars, normal; Mission_Name: IUE Description: We present a library of mean ultraviolet stellar energy distributions derived from International Ultraviolet Explorer (IUE) low-resolution spectrophotometry of 216 stars. The library is intended to facilitate interpretation of the composite UV light of stellar populations such as star clusters and galaxies. The spectra cover 1205-3185 Angstroms with a spectral resolution of approximately 6 A. The individual stellar spectra were corrected for interstellar extinction (using the Savage-Mathis law), converted to a common flux scale, and interpolated to a common wavelength scale. Stars were combined into standard groups according to their intrinsic continuum colors, observed UV spectral morphology, MK luminosity class, and metal abundance. The library consists of 56 groups: 21 dwarf (V), 8 subgiant (IV), 16 giant (III), and 11 supergiant (I+II) groups, covering O3-M4 spectral types. A metal-poor sequence is included, containing four dwarf and two giant groups, as is a metal-enhanced sequence with a single dwarf, subgiant, and giant group. More information on the library compilation and descriptions of the behavior of spectral indices characterizing the continuum and strong absorption features are given in Fanelli et al. (1992). The spectra themselves (in the uvgroups.fit file) were previously released in the AAS CD-ROM Series Volume VII (1996); see Leitherer et al. (1996). Introduction: Each mean group spectral energy distribution (SED) is a weighted average of good quality, extinction-corrected, normalized IUE spectra for a number of stars (ranging from 2 to 12). Assignments to groups were based on actual UV SED properties, rather than optical-band spectral classifications, and were adjusted to minimize the dispersion within a group and maximize the difference with adjacent groups. The SEDs are given in units of flux per unit wavelength normalized to the V band, i.e. F_lam(lam) / , where the mean V-band flux in units of (ergs/s cm^2 A) was derived from = dex[-0.4*(V+21.175)]. The mean group SEDs are presented in a FITS image file named uvgroups.fit. This contains a single data array with 57 rows and 1245 columns. The first row contains the 1245 element wavelength vector. The remaining 56 rows contain the individual group SEDs in the order listed in the Group Library Contents (Table 1) below. The S/N for stars cooler than about 8000 K usually becomes very low in the far-UV in the available spectra. Shortward of a cutoff wavelength (listed in Table 5 of Fanelli et al. 1992), which depends on temperature, we have entered the dummy value 1.0e-20 in the data vectors. Flux measures for cool stars just longward of this range are often of low quality, as will be apparent from increased flux scatter; in a few cases, negative flux values occur in this region. We also present two files containing values for the spectral indices measuring lines and continuum structure which were defined in Fanelli et al. (1992). Definitions for these indices are given in Table 2 below. The values in the files are updated from those in Table 7 of Fanelli et al. (1992) in two ways. First, we have used an improved integration scheme to average fluxes in bands; second, we have corrected an error in the tabulation of the continuum colors 2600-V and 3000-V. Owing to a transcription error, the original published values were for narrow bands centered in the continuum windows rather than for averages over them. Because of the rapid changes of flux with wavelength in the UV, the new values are often very different from the original ones. File Summary: ------------------------------------------------------------ FileName Lrecl Records Explanations ------------------------------------------------------------ ReadMe 80 . This file uvgroups.fit . 57 Group wavelengths, fluxes in [1245x57] image format. Floating point. fuvind.dat 162 56 Far-UV spectral indices muvind.dat 142 56 Mid-UV spectral indices ----------------------------------------------------------- Table 1: UV Group Library Contents ------------------------------------------------------------------------ Entry Name # M_V Mass [Fe/H] B-V U-B (1) (2) (3) (4) (5) (6) (7) (8) ------------------------------------------------------------------------ 1 [Wavelengths] 2 O3-6 V 5 -5.50 50.00 0.00 -0.33 -1.19 3 O7-B0 V 4 -4.50 20.00 0.00 -0.31 -1.12 4 B1-1.5 V 3 -3.00 13.00 0.00 -0.26 -0.95 5 B2-4 V 5 -1.80 8.00 0.00 -0.21 -0.73 6 B5-8 V 6 -0.70 5.00 0.00 -0.14 -0.46 7 B9-9.5 V 3 0.30 3.30 0.00 -0.05 -0.17 8 A0-2 V 5 1.00 2.70 0.00 0.02 -0.01 9 A5-8 V 4 2.15 1.80 0.00 0.19 0.09 10 A9-F3 V 4 2.95 1.50 0.00 0.33 0.03 11 F5-7 V 7 3.60 1.30 0.00 0.45 0.00 12 F8-9 V 7 4.10 1.15 0.05 0.55 0.06 13 F5-6 V MP 2 3.60 1.30 -0.68 0.44 -0.13 14 F7-9 V MP 4 4.10 1.15 -0.47 0.54 -0.04 15 G0-5 V 12 4.75 1.00 0.03 0.61 0.11 16 G0-2 V MP 6 4.75 1.00 -0.50 0.60 0.03 17 G0-5 V MR 3 4.75 1.00 0.28 0.69 0.24 18 G6-9 V 5 5.50 0.85 0.11 0.77 0.35 19 G8 V MP 3 5.50 0.85 -0.43 0.72 0.20 20 K0-1 V 4 6.05 0.80 0.11 0.88 0.59 21 K2-3 V 2 6.70 0.72 -0.10 0.94 0.74 22 K5-7 V 2 8.10 0.58 -0.11 1.27 1.17 23 O9-B0 IV 2 -5.00 20.00 0.00 -0.30 -1.10 24 B2-5 IV 5 -2.40 7.00 0.00 -0.20 -0.73 25 B8-9 IV 2 -0.45 4.00 0.00 -0.09 -0.27 26 A7-F0 IV 2 2.00 1.80 0.00 0.26 0.07 27 F2-7 IV 3 2.50 1.40 -0.21 0.42 0.04 28 G0-2 IV 2 3.00 1.20 0.00 0.64 0.16 29 G5-8 IV MR 3 3.10 1.20 0.30 0.79 0.44 30 G8-K1 IV 5 3.10 1.20 0.04 1.01 0.85 31 O5-6 III 2 -6.00 50.00 0.00 -0.32 -1.18 32 B0-2 III 5 -4.40 20.00 0.00 -0.26 -0.96 33 B3-6 III 5 -2.40 8.00 0.00 -0.17 -0.62 34 B7-9 III 3 -1.10 5.00 0.00 -0.10 -0.32 35 A3-6 III 2 0.70 3.00 0.00 0.13 0.11 36 A9-F6 III 5 1.50 1.70 0.00 0.36 0.08 37 F6 III MP 1 1.50 1.70 -0.40 0.44 -0.01 38 G0-5 III 3 0.95 1.20 0.00 0.75 0.33 39 G5-K0 III 6 0.80 1.20 0.10 0.98 0.82 40 K0-2 III 4 0.60 1.20 0.00 1.08 1.01 41 K0-2 III MP 3 0.60 1.20 -0.45 1.10 0.95 42 K2 III 3 0.50 1.20 0.10 1.20 1.30 43 K3 III 3 0.30 1.20 0.00 1.34 1.50 44 K2-3 III MR 4 0.40 1.20 0.31 1.23 1.34 45 K4-5 III 3 -0.10 1.20 -0.15 1.52 1.87 46 K7-M3 III 4 -0.50 1.20 0.00 1.57 1.86 47 O4-9 I 4 -6.80 50.00 0.00 -0.30 -1.15 48 B0-2 I 7 -6.50 25.00 0.00 -0.22 -1.02 49 B3-5 I 5 -6.50 20.00 0.00 -0.11 -0.71 50 B6-9 I 3 -6.50 20.00 0.00 -0.04 -0.46 51 A0-2 I 3 -6.50 15.00 0.00 0.03 -0.25 52 A5-F0 I 2 -6.50 15.00 0.00 0.13 0.04 53 F2-8 I 3 -6.50 15.00 0.00 0.38 0.30 54 G0-3 I 5 -6.50 15.00 0.00 0.84 0.60 55 G5-8 I 2 -6.20 15.00 0.00 1.09 0.82 56 K2-3 I 2 -6.00 15.00 0.00 1.35 1.30 57 K5-M4 I 4 -5.70 15.00 0.00 1.64 1.87 ----------------------------------------------------------------------- Notes to Table 1: Col (1) -- Row number in uvgroups.fit data array. Col (2) -- Assigned group name based on the range of stellar types in each group. Col (3) -- The number of stars used to construct the group. Col (4) -- Adopted absolute visual magnitude derived from Schmidt-Kaler (1982) and Humphreys & McElroy (1984). Col (5) -- Adopted mass in solar units determined from the same sources. Col (6) -- Mean group metallicity. The average is derived from all group members with a measured abundance. Since abundance information is complete for only a few groups, these values are only indicative of the true mean group metallicity. Entries of 0.00 indicate that the stars are probably near solar abundance but that individual estimates are not available. Col (7) -- Adopted intrinsic (B-V) color. For stellar types O3 to F3, V-III and all supergiants this value is the mean intrinsic color tabluated by Schmidt-Kaler (1982). For types F5 to M3, V-III the given value is the mean observed (B-V) color, averaged over all members of the group. No extinction corrections are applied to the latter SEDs. Col (8) -- Adopted U-B color, derived as for B-V. ---------------------------------------------------------------------------- Table 2: Band Definitions for UV Spectral Indices ----------------------------------------------------------------------------- Index Name Band 1 Band 2 Band 3 Line Feature (1) (2) (3) (4) (5) ----------------------------------------------------------------------------- FAR-UV ---------- 1400 1330,1530 (Continuum) 1700 1580,1780 (Continuum) BL 1302 1270,1290 1345,1365 1292,1312 Si III, Si II, O I Si IV 1397 1345,1365 1475,1495 1387,1407 Si IV (1393.8,1402.8) BL 1425 1345,1365 1475,1495 1415,1435 C II, Si III, Fe IV, Fe V Fe V 1453 1345,1365 1475,1495 1440,1466 Fe V C IV 1540 1500,1520 1577,1597 1530,1550 C IV (1548.2,1550.8) absorp C IV 1550 1500,1520 1577,1597 1540,1560 C IV center C IV 1560 1500,1520 1577,1597 1550,1570 C IV emiss C IV PCyg 1530,1550 1550,1570 C IV absorp/emiss BL 1617 1577,1597 1685,1705 1604,1630 Fe IV BL 1664 1577,1597 1685,1705 1651,1677 C I, Al II BL 1719 1685,1705 1803,1823 1709,1729 N IV, Si IV, Al II BL 1853 1803,1823 1885,1915 1838,1868 Al II, Al III, Fe II, Fe III MID-UV --------- 2600 2470,2670 (Continuum) 3000 2930,3130 (Continuum) BR 26 2596,2623 2647,2673 2600 A spectral break BR 29 2818,2838 2906,2936 2900 A spectral break Fe II 2402 2285,2325 2432,2458 2382,2422 Fe II BL 2538 2432,2458 2562,2588 2520,2556 Fe I? Fe II 2609 2562,2588 2647,2673 2596,2622 Fe II Mg II 2800 2762,2782 2818,2838 2784,2814 Mg II (2795.5,2802.7) Mg I 2852 2818,2838 2906,2936 2839,2865 Mg I Mg Wide 2470,2670 2930,3130 2670,2870 Mg I + Mg II Fe I 3000 2906,2936 3031,3051 2965,3025 Fe I BL 3096 3031,3051 3115,3155 3086,3106 Al I, Fe I, Ni I? ----------------------------------------------------------------------------- Notes to Table 2: Note 1: The wavelength pairs in Cols. (2), (3), and (4) are the shortest and longest wavelengths, respectively, in the band. Bandwidths vary. Units: Angstroms. Note 2: Definition of spectral indices (all expressed in magnitudes) If all three bands are present, the spectral index measures an emission or absorption feature in Band 3 and is defined as: I = -2.5*log_10(F3/FC), where F3 is the mean flux in Band 3 and FC is a pseudocontinuum flux at Band 3 linearly interpolated between Bands 1 and 2. If only Band 1 and Band 2 are present, the spectral index measures a continuum "break" between the bands and is defined as: I = -2.5*log_10(F1/F2), where F1 and F2 are the mean fluxes in Bands 1 and 2, respectively. If only Band 1 is present, the spectral index is a UV-V color index defined as I = -2.5*log_10(F1), where F1 is the mean flux in Band 1 (already normalized to the V-band in the mean group spectra) Note 3: "BL" stands for a "blanketing" index---i.e. where several species contribute comparably to the absorption in the feature band Note 4: The fuvind.dat and muvind.dat files contain entries of -99 for indices where any band contains a low quality flux measurement. This occurs mainly for cooler stars at shorter wavelengths. --------------------------------------------------------------------------- Byte-By-Byte Description of File: fuvind.dat --------------------------------------------------------------------------- Bytes Format Units Label Explanations 1-12 A12 ID Group Name 16-22 F7.3 Mags B-V Optical broad-band color 26-32 F7.3 Mags 14-V 1400-V UV-optical color 36-42 F7.3 Mags 17-V 1700-V UV-optical color 46-52 F7.3 Mags BL1302 BL 1302 line index 56-62 F7.3 Mags Si1397 Si IV 1397 line index 66-72 F7.3 Mags BL1425 BL 1425 line index 76-82 F7.3 Mags Fe1453 Fe V 1453 line index 86-92 F7.3 Mags C1540 C IV 1540 abs line index 96-102 F7.3 Mags C1550 C IV 1550 cent line index 106-112 F7.3 Mags C1560 C IV 1560 emiss line index 116-122 F7.3 Mags CPcyg C IV PCyg line index 126-132 F7.3 Mags BL1627 BL 1627 line index 136-142 F7.3 Mags BL1664 BL 1664 line index 146-152 F7.3 Mags BL1719 BL 1719 line index 156-162 F7.3 Mags BL1853 BL 1853 line index --------------------------------------------------------------------------- Byte-By-Byte Description of File: muvind.dat --------------------------------------------------------------------------- Bytes Format Units Label Explanations 1-12 A12 ID Group Name 16-22 F7.3 Mags B-V Optical broad-band color 26-32 F7.3 Mags 26-V 2600-V UV-optical color 36-42 F7.3 Mags 30-V 3000-V UV-optical color 46-52 F7.3 Mags BR26 2600 A spectral break index 56-62 F7.3 Mags BR29 2900 A spectral break index 66-72 F7.3 Mags Fe2402 Fe II 2402 line index 76-82 F7.3 Mags BL2538 BL 2538 line index 86-92 F7.3 Mags Fe2609 Fe II 2609 line index 96-102 F7.3 Mags MgII Mg II 2800 line index 106-112 F7.3 Mags MgI Mg I 2852 line index 116-122 F7.3 Mags MgW Mg Wide (MgI + Mg II) line index 126-132 F7.3 Mags Fe3000 Fe I 3000 line index 136-142 F7.3 Mags BL3096 BL 3096 line index ---------------------------------------------------------------------------- References: Humphreys R.M., & McElroy D.B., 1984, ApJ, 284, 565 Schmidt-Kaler T., 1982, "Numerical Data and Functional Relationships In Science and Technology" Group VI, Vol. 2b, ed. K. Schaifers & H. H. Voigt (Berlin: Springer-Verlag)