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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. <Astrophys. J. Suppl. Ser. 82, 197 (1992)> =1992ApJS...82..197F
ADC_Keywords: Spectra, ultraviolet; Stars, normal 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 behaviour of spectral indices characterizing the continuum and strong absorption features are given in the paper. The spectra themselves (in the uvgroups.fit file) were previously released in the AAS CD-ROM Series Volume VII (1996); see Leitherer et al. "A Database for Galaxy Evolution Modeling" (1996PASP..108..996L). 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(λ)/<F(V)>, where the mean V-band flux <F(V)>, expressed in units of erg/s/cm2/Å (=10mW/m2/nm) was computed as <F(V)> = dexp[-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 ("groups.dat" file). The S/N for stars cooler than about 8000K 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 are defined in the paper and summarized in the "Note (G1)" section below. The values in the files are updated from those in Table 7 of the paper 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 groups.dat 69 56 Definition of the 56 groups uvgroups.fit 2880 100 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
See also: VI/110 : Final Merged Log of IUE Observations (NASA-ESA, 2000) Byte-by-byte Description of file: groups.dat
Bytes Format Units Label Explanations
5- 6 I2 --- Row [2,57] Row number in uvgroups.fit data array. 12- 21 A10 --- SpGr Spectral group name (range of temperature and luminosity classes; includes "mp" and "mr" for metal-poor and meta-rich group). 25- 26 I2 --- Nst Number of stars used to construct the group. 33- 37 F5.2 mag VMAG Adopted absolute visual magnitude derived from Schmidt-Kaler (1982) and Humphreys & McElroy (1984ApJ...284..565H). 41- 45 F5.2 Msun M Adopted mass determined from the same sources. 49- 53 F5.2 [Sun] [Fe/H] Mean group metallicity (1) 57- 61 F5.2 mag B-V Adopted intrinsic (B-V) color (2) 65- 69 F5.2 mag U-B Adopted U-B color, derived as for B-V.
Note (1): 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. Note (2): for stellar types O3 to F3, V-III and all supergiants this value is the mean intrinsic color tabulated 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.
Byte-by-byte Description of file: fuvind.dat
Bytes Format Units Label Explanations
2- 11 A10 --- SpGr Group Name 17- 21 F5.2 mag B-V ?=-9.999 Optical broad-band color 22 A1 --- --- [0] 27- 32 F6.3 mag 14-V ?=-9.999 1400-V UV-optical color (G1) 37- 42 F6.3 mag 17-V ?=-9.999 1700-V UV-optical color (G1) 47- 52 F6.3 mag BL1302 ?=-9.999 BL 1302 line blanketing index (G1) 57- 62 F6.3 mag Si1397 ?=-9.999 SiIV 1397 line index (G1) 67- 72 F6.3 mag BL1425 ?=-9.999 BL 1425 line blanketing index (G1) 77- 82 F6.3 mag Fe1453 ?=-9.999 FeV 1453 line index (G1) 87- 92 F6.3 mag C1540 ?=-9.999 CIV 1540 abs line index (G1) 97-102 F6.3 mag C1550 ?=-9.999 CIV 1550 cent line index (G1) 107-112 F6.3 mag C1560 ?=-9.999 CIV 1560 emiss line index (G1) 117-122 F6.3 mag CPcyg ?=-9.999 CIV PCyg line index (G1) 127-132 F6.3 mag BL1627 ?=-9.999 BL 1627 line blanketing index (G1) 137-142 F6.3 mag BL1664 ?=-9.999 BL 1664 line blanketing index (G1) 147-152 F6.3 mag BL1719 ?=-9.999 BL 1719 line blanketing index (G1) 157-162 F6.3 mag BL1853 ?=-9.999 BL 1853 line blanketing index (G1)
Byte-by-byte Description of file: muvind.dat
Bytes Format Units Label Explanations
2- 11 A10 --- SpGr Group Name 17- 21 F5.2 mag B-V ?=-9.999 Optical broad-band color 22 A1 --- --- [0] 27- 32 F6.3 mag 26-V ?=-9.999 2600-V UV-optical color (G1) 37- 42 F6.3 mag 30-V ?=-9.999 3000-V UV-optical color (G1) 47- 52 F6.3 mag BR26 ?=-9.999 2600Å spectral break index (G1) 57- 62 F6.3 mag BR29 ?=-9.999 2900Å spectral break index (G1) 67- 72 F6.3 mag Fe2402 ?=-9.999 FeII 2402 line index (G1) 77- 82 F6.3 mag BL2538 ?=-9.999 BL 2538 line blanketing index (G1) 87- 92 F6.3 mag Fe2609 ?=-9.999 FeII 2609 line index (G1) 97-102 F6.3 mag MgII ?=-9.999 MgII 2800 line index (G1) 107-112 F6.3 mag MgI ?=-9.999 MgI 2852 line index (G1) 117-122 F6.3 mag MgW ?=-9.999 Mg Wide (MgI + MgII) line index (G1) 127-132 F6.3 mag Fe3000 ?=-9.999 FeI 3000 line index (G1) 137-142 F6.3 mag BL3096 ?=-9.999 BL 3096 line blanketing index (G1)
Global Notes: Note (G1): Definitions for UV Spectral Indices. The following table summarized the definition of the spectral indices ("BL" stands for a "blanketing" index -- i.e. where several species contribute comparably to the absorption in the feature band) -------------------------------------------------------------------------- Index Name Band 1 Band 2 Band 3 Line Feature (1) (2) (3) (4) (5) -------------------------------------------------------------------------- FAR-UV --------- 14-V 1330,1530 (Continuum) 17-V 1580,1780 (Continuum) BL1302 1270,1290 1345,1365 1292,1312 SiIII, SiII, OI Si1397 1345,1365 1475,1495 1387,1407 SiIV (1393.8,1402.8) BL1425 1345,1365 1475,1495 1415,1435 CII, SiIII, FeIV, FeV Fe1453 1345,1365 1475,1495 1440,1466 FeV C1540 1500,1520 1577,1597 1530,1550 CIV (1548.2,1550.8) absorp C1550 1500,1520 1577,1597 1540,1560 CIV center C1560 1500,1520 1577,1597 1550,1570 CIV emiss CPCyg 1530,1550 1550,1570 CIV absorp/emiss BL1617 1577,1597 1685,1705 1604,1630 FeIV BL1664 1577,1597 1685,1705 1651,1677 CI, AlII BL1719 1685,1705 1803,1823 1709,1729 NIV, SiIV, AlII BL1853 1803,1823 1885,1915 1838,1868 AlII, AlIII, FeII, FeIII MID-UV --------- 26-V 2470,2670 (Continuum) 30-V 2930,3130 (Continuum) BR26 2596,2623 2647,2673 2600Å spectral break BR29 2818,2838 2906,2936 2900Å spectral break Fe2402 2285,2325 2432,2458 2382,2422 FeII BL2538 2432,2458 2562,2588 2520,2556 FeI? Fe2609 2562,2588 2647,2673 2596,2622 FeII Mg2800 2762,2782 2818,2838 2784,2814 MgII (2795.5,2802.7) Mg2852 2818,2838 2906,2936 2839,2865 MgI MgWide 2470,2670 2930,3130 2670,2870 MgI + MgII Fe3000 2906,2936 3031,3051 2965,3025 FeI BL3096 3031,3051 3115,3155 3086,3106 AlI, FeI, NiI? -------------------------------------------------------------------------- The wavelength pairs in Cols. (2), (3), and (4) are the shortest and longest wavelengths, respectively, in the band. Bandwidths vary. Units: Angstroms (Å = 0.1nm). 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(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(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(F1) where F1 is the mean flux in Band 1 (already normalized to the V-band in the mean group spectra)
References: 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) History: * 12-Jul-1999: prepared by Robert W. O'Connell [UVa] & James E. Gass [ADC/SSDOO] * 02-Mar-2011: Description revisited, added "groups.dat" file Francois Ochsenbein [CDS]
(End) Robert W. O'Connell [UVa] & James E. Gass [ADC/SSDOO] 12-Jul-1999
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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