220 research outputs found
For the Public Good
[Excerpt] This early warning meeting began the labor and community struggle in Hammond, Indiana to save LaSalle Steel, a 350-worker specialty products steel mill owned by Texas-based Quanex Corporation. A year later, the plant would expand rather than shut down, the union at LaSalle would be stronger than ever, and the labor-community coalition led by the Calumet Project for Industrial Jobs would celebrate its biggest anti-shutdown victory yet
Workshop Training: Union Membership Mobilization and Collective Bargaining in an Open Shop Environment
Operating in a Right to Work Environment: The Experience in Florid
Extended Stromgren Photoelectric Photometry in NGC 752
Photoelectric photometry on the extended Stromgren system (uvbyCa) is
presented for 7 giants and 21 main sequence stars in the old open cluster, NGC
752. Analysis of the hk data for the turnoff stars yields a new determination
of the cluster mean metallicity. From 10 single-star members, [Fe/H] = -0.06
+/- 0.03, where the error quoted is the standard error of the mean and the
Hyades abundance is set at [Fe/H] = +0.12. This result is unchanged if all 20
stars within the limits of the hk metallicity calibration are included. The
derived [Fe/H] is in excellent agreement with past estimates using
properly-zeroed m1 data, transformed moderate-dispersion spectroscopy, and
recent high dispersion spectroscopy.Comment: 14 tex'd pages including 2 tables; 2 separate files with eps figures
Accepted for PASP March 200
uvbyCa H beta CCD Photometry of Clusters. VII. The Intermediate-Age Anticenter Cluster Melotte 71
CCD photometry on the intermediate-band uvbyCa H beta system is presented for
the anticenter, intermediate-age open cluster, Melotte 71. Restricting the data
to probable single members of the cluster using the color-magnitude diagram and
the photometric indices alone generates a sample of 48 F dwarfs on the
unevolved main sequence. The average E(b-y) = 0.148 +/- 0.003 (s.e.m.) or
E(B-V) = 0.202 +/- 0.004 (s.e.m.), where the errors refer to internal errors
alone. With this reddening, [Fe/H] is derived from both m1 and hk, using H beta
and b-y as the temperature index, with excellent agreement among the four
approaches and a final weighted average of [Fe/H] = -0.17 +/- 0.02 (s.e.m.) for
the cluster, on a scale where the Hyades has [Fe/H] = +0.12. When adjusted for
the higher reddening estimate, the previous metallicity estimates from
Washington photometry and from spectroscopy are now in agreement with the
intermediate-band result. From comparisons to isochrones of appropriate
metallicity, the cluster age and distance are determined as 0.9 +/- 0.1 Gyr and
(m-M) = 12.2 +/- 0.1 or (m-M)_0 = 11.6 +/- 0.1. At this distance from the sun,
Mel 71 has a galactocentric distance of 10.0 kpc on a scale where the sun is
8.5 kpc from the galactic center. Based upon its age, distance, and elemental
abundances, Mel 71 appears to be a less populous analog to NGC 3960.Comment: Accepted for Astronomical Journal. 38 page latex file includes 11
figures and short version of data table. Full table will appear in online AJ
or may be requested from author
A Prediction of Brown Dwarfs in Ultracold Molecular Gas
A recent model for the stellar initial mass function (IMF), in which the
stellar masses are randomly sampled down to the thermal Jeans mass from
hierarchically structured pre-stellar clouds, predicts that regions of
ultra-cold CO gas, such as those recently found in nearby galaxies by Allen and
collaborators, should make an abundance of Brown Dwarfs with relatively few
normal stars. This result comes from the low value of the thermal Jeans mass,
considering that the hierarchical cloud model always gives the Salpeter IMF
slope above this lower mass limit. The ultracold CO clouds in the inner disk of
M31 have T~3K and pressures that are probably 10 times higher than in the solar
neighborhood. This gives a mass at the peak of the IMF equal to 0.01 Msun, well
below the Brown Dwarf limit of 0.08 Msun. Using a functional approximation to
the IMF, the ultracold clouds would have 50% of the star-like mass and 90% of
the objects below the Brown Dwarf limit. The brightest of the Brown Dwarfs in
M31 should have an apparent, extinction-corrected K-band magnitude of ~21 mag
in their pre-main sequence phase.Comment: 13 pages, 2 figures, to be published in Astrophysical Journal, Vol
522, September 10, 199
vbyCaHbeta CCD Photometry of Clusters. VI. The Metal-Deficient Open Cluster NGC 2420
CCD photometry on the intermediate-band vbyCaHbeta system is presented for
the metal-deficient open cluster, NGC 2420. Restricting the data to probable
single members of the cluster using the CMD and the photometric indices alone
generates a sample of 106 stars at the cluster turnoff. The average E(b-y) =
0.03 +/- 0.003 (s.e.m.) or E(B-V) = 0.050 +/- 0.004 (s.e.m.), where the errors
refer to internal errors alone. With this reddening, [Fe/H] is derived from
both m1 and hk, using b-y and Hbeta as the temperature index. The agreement
among the four approaches is reasonable, leading to a final weighted average of
[Fe/H] = -0.37 +/- 0.05 (s.e.m.) for the cluster, on a scale where the Hyades
has [Fe/H] = +0.12. When combined with the abundances from DDO photometry and
from recalibrated low-resolution spectroscopy, the mean metallicity becomes
[Fe/H] = -0.32 +/- 0.03. It is also demonstrated that the average cluster
abundances based upon either DDO data or low-resolution spectroscopy are
consistently reliable to 0.05 dex or better, contrary to published attempts to
establish an open cluster metallicity scale using simplistic offset corrections
among different surveys.Comment: scheduled for Jan. 2006 AJ; 33 pages, latex, includes 7 figures and 2
table
A Comparison of the Chemical Evolutionary Histories of the Galactic Thin Disk and Thick Disk Stellar Populations
We have studied 23 long-lived G dwarfs that belong to the thin disk and thick
disk stellar populations. Abundances have been derived for 24 elements: O, Na,
Mg, Al, Si, Ca, Ti, Sc, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sr, Y, Zr, Ba, La, Ce,
Nd, and Eu. We find that the behavior of [alpha/Fe] and [Eu/Fe] vs. [Fe/H] are
quite different for the two populations. As has long been known, the thin disk
O, Mg, Si, Ca, and Ti ratios are enhanced relative to iron at the lowest
metallicities, and decline toward solar values as [Fe/H] rises above -1.0. For
the thick disk, the decline in [alpha/Fe] and [Eu/Fe] does not begin at [Fe/H]
= -1.0, but at -0.4. Other elements share this behavior, including Sc, Co, and
Zn, suggesting that at least in the chemical enrichment history of the thick
disk, these elements were manufactured in similar-mass stars. Combining our
results for the oldest and longest-lived stars with prior work, we find clear
signs for an independent origin for the Galactic thick disk. (Abridged)Comment: 48 pages and 20 figures, accepted for publication in the Astronomical
Journa
vbyCaHbeta CCD Photometry of Clusters. VIII. The Super-Metal Rich, Old Open Cluster NGC 6791
CCD photometry on the intermediate-band vbyCaHbeta system is presented for
the metal-rich, old open cluster, NGC 6791. Preliminary analysis led to [Fe/H]
above +0.4 with an anomalously high reddening and an age below 5 Gyr. A revised
calibration between (b-y)_0 and [Fe/H] at a given temperature shows that the
traditional color-metallicity relations underestimate the color of the turnoff
stars at high metallicity. With the revised relation, the metallicity from hk
and the reddening for NGC 6791 become [Fe/H] = +0.45 +/- 0.04 and E(b-y) =
0.113 +/- 0.012 or E(B-V) = 0.155 +/- 0.016. Using the same technique,
reanalysis of the photometry for NGC 6253 produces [Fe/H] = +0.58 +/-0.04 and
E(b-y) = 0.120 +/- 0.018 or E(B-V) = 0.160 +/- 0.025. The errors quoted include
both the internal and external errors. For NGC 6791, the metallicity from m_1
is a factor of two below that from hk, a result that may be coupled to the
consistently low metal abundance from DDO photometry of the cluster and the
C-deficiency found from high dispersion spectroscopy. E(B-V) is the same value
predicted from Galactic reddening maps. With E(B-V) = 0.15 and [Fe/H] = +0.45,
the available isochrones predict an age of 7.0 +/- 1.0 Gyr and an apparent
modulus of (m-M) = 13.60 +/- 0.15, with the dominant source of the uncertainty
arising from inconsistencies among the isochrones. The reanalysis of NGC 6253
with the revised lower reddening confirms that on both the hk and m_1
metallicity scales, NGC 6253, while less than half the age of NGC 6791, remains
at least as metal-rich as NGC 6791, if not richer.Comment: Accepted for Astronomical Journal. 42 p. latex file includes 11
figures and 3 tables, one of which is a short version of a data table to
appear in online AJ in its entiret
Caby Photometry of the Hyades: Comparisons to the Field Stars
Intermediate-band photometry of the Hyades cluster on the Caby system is
presented for dwarf stars ranging from spectral type A through late K. A mean
hk, b-y relation is constructed using only single stars without anomalous
atmospheres and compared to the field stars of the solar neighborhood. For the
F dwarfs, the Hyades relation defines an approximate LOWER bound in the
two-color diagram, consistent with an [Fe/H] between +0.10 and +0.15. These
index-color diagrams follow the common convention of presenting stars with
highest abundance at the bottom of the plot although the index values for the
metal-rich stars are numerically larger. For field F dwarfs in the range [Fe/H]
between +0.4 and -1.0, [Fe/H] = -5.6 delta-hk + 0.125, with no evidence for a
color dependence in the slope. For the G and K dwarfs, the Hyades mean relation
crosses the field star distribution in the two-color diagram, defining an
approximate UPPER bound for the local disk stars. Stars found above the Hyades
stars fall in at least one of three categories: [Fe/H] below -0.7, [Fe/H] above
that of the Hyades, or chromospherically active. It is concluded that, contrary
to the predictions of model atmospheres, the hk index for cool dwarfs at a
given color hits a maximum value for stars below solar composition and, with
increasing [Fe/H] above some critical value, declines. This trend is
consistent, however, with the predictions from synthetic indices based upon
much narrower Ca filters where the crossover is caused by the metallicity
sensitivity of b-y.Comment: 13 pages, 9 eps figures, 1 tex table, 1 ascii tabl
A UBVI and uvbyCaHbeta Analysis of the Intermediate-Age Open Cluster, NGC 5822
NGC 5822 is a richly populated, moderately nearby, intermediate-age open
cluster covering an area larger than the full moon on the sky. A CCD survey of
the cluster on the UBVI and uvbyCaHbeta systems shows that the cluster is
superposed upon a heavily reddened field of background stars with E(B-V) > 0.35
mag, while the cluster has small and uniform reddening at E(b-y) = 0.075 +/-
0.008 mag or E(B-V) = 0.103 +/- 0.011 mag, based upon 48 and 61 probable A and
F dwarf single-star members, respectively. The errors quoted include both
internal photometric precision and external photometric uncertainties. The
metallicity derived from 61 probable single F-star members is [Fe/H] = -0.058
+/- 0.027 (sem) from m_1 and 0.010 +/- 0.020 (sem) from hk, for a weighted
average of [Fe/H] = -0.019 +/- 0.023, where the errors refer to the internal
errors from the photometry alone. With reddening and metallicity fixed, the
cluster age and apparent distance modulus are obtained through a comparison to
appropriate isochrones in both VI and BV, producing 0.9 +/- 0.1 Gyr and 9.85
+/- 0.15, respectively. The giant branch remains dominated by two distinct
clumps of stars, though the brighter clump seems a better match to the
core-He-burning phase while the fainter clump straddles the first-ascent red
giant branch. Four potential new clump members have been identified, equally
split between the two groups. Reanalysis of the UBV two-color data extending
well down the main sequence shows it to be optimally matched by reddening near
E(B-V) = 0.10 rather than the older value of 0.15, leading to [Fe/H] between
-0.16 and 0.00 from the ultraviolet excess of the unevolved dwarfs. The impact
of the lower reddening and younger age of the cluster on previous analyses of
the cluster is discussed.Comment: 20 figures and 5 tables (portions of data tables 3 and 5 only
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