359 research outputs found
Validation of the Childhood Career Development Scale Among Italian Middle School Students
During early adolescence, individuals engage in exploring educational opportunities, beginning to develop a career identity, contemplate future careers, and make tentative career decisions. Choices made during this period may have a strong effect on one\u2019s academic and career future, and in many countries, young adolescents must make important and sometimes final academic and career choices that impact the rest of their lives. Despite this, research on early adolescence is severely lacking. To address this gap, a validation study of the Childhood Career Development Scale (CCDS) was conducted with a young adolescent Italian sample. Consistent with previous research with younger samples, support was found for an eight-factor structure of the CCDS. Convergent validity was supported by positive associations with exploration, students\u2019 ideas, attitudes, and behaviors regarding their academic and career future and career self-efficacy. These findings support Super\u2019s dimensional model of childhood career development through early adolescence as originally theorized
Closed-form sums for some perturbation series involving associated Laguerre polynomials
Infinite series sum_{n=1}^infty {(alpha/2)_n / (n n!)}_1F_1(-n, gamma, x^2),
where_1F_1(-n, gamma, x^2)={n!_(gamma)_n}L_n^(gamma-1)(x^2), appear in the
first-order perturbation correction for the wavefunction of the generalized
spiked harmonic oscillator Hamiltonian H = -d^2/dx^2 + B x^2 + A/x^2 +
lambda/x^alpha 0 0, A >= 0. It is proved that the
series is convergent for all x > 0 and 2 gamma > alpha, where gamma = 1 +
(1/2)sqrt(1+4A). Closed-form sums are presented for these series for the cases
alpha = 2, 4, and 6. A general formula for finding the sum for alpha/2 = 2 + m,
m = 0,1,2, ..., in terms of associated Laguerre polynomials, is also provided.Comment: 16 page
NGC 602 Environment, Kinematics and Origins
The young star cluster NGC 602 and its associated HII region, N90, formed in
a relatively isolated and diffuse environment in the Wing of the Small
Magellanic Cloud. Its isolation from other regions of massive star formation
and the relatively simple surrounding HI shell structure allows us to constrain
the processes that may have led to its formation and to study conditions
leading to massive star formation. We use images from Hubble Space Telescope
and high resolution echelle spectrographic data from the Anglo-Australian
Telescope along with 21-cm neutral hydrogen (HI) spectrum survey data and the
shell catalogue derived from it to establish a likely evolutionary scenario
leading to the formation of NGC 602. We identify a distinct HI cloud component
that is likely the progenitor cloud of the cluster and HII region which
probably formed in blister fashion from the cloud's periphery. We also find
that the past interaction of HI shells can explain the current location and
radial velocity of the nebula. The surrounding Interstellar Medium is diffuse
and dust-poor as demonstrated by a low visual optical depth throughout the
nebula and an average HI density of the progenitor cloud estimated at 1 cm^-3.
These conditions suggest that the NGC 602 star formation event was produced by
compression and turbulence associated with HI shell interactions. It therefore
represents a single star forming event in a low gas density region.Comment: Accepted for publication in PASP. 25 pages, 10 figure
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
The initial stellar mass function from random sampling in hierarchical clouds II: statistical fluctuations and a mass dependence for starbirth positions and times
Observed variations in the slope of the initial stellar mass function are
shown to be consistent with a model in which the protostellar gas is randomly
sampled from hierarchical clouds at a rate proportional to the square root of
the local density. RMS variations in the IMF slope around the Salpeter value
are +/- 0.4 when only 100 stars are observed, and +/- 0.1 when 1000 stars are
observed. The hierarchical-sampling model also reproduces the tendency for
massive stars to form closer to the center of a cloud, at a time somewhat later
than the formation time of the lower mass stars. The assumed density dependence
for the star formation rate is shown to be appropriate for turbulence
compression, magnetic diffusion, gravitational collapse, and clump or
wavepacket coalescence. The low mass flattening in the IMF comes from the
inability of gas to form stars below the thermal Jeans mass at typical
temperatures and pressures. Consideration of heating and cooling processes
indicate why the thermal Jeans mass should be nearly constant in normal
environments, and why it might increase in some starburst regions. The steep
IMF in the extreme field is not explained by the model, but other origins are
suggested.Comment: 21 pages, 8 figures, scheduled for ApJ vol. 515, April 10, 199
The Stellar Mass Distribution in the Giant Star Forming Region NGC 346
Deep F555W and F814W Hubble Space Telescope ACS images are the basis for a
study of the present day mass function (PDMF) of NGC346, the largest active
star forming region in the Small Magellanic Cloud (SMC). We find a PDMF slope
of Gamma=-1.43+/-0.18 in the mass range 0.8-60 Mo, in excellent agreement with
the Salpeter Initial Mass Function (IMF) in the solar neighborhood. Caveats on
the conversion of the PDMF to the IMF are discussed. The PDMF slope changes, as
a function of the radial distance from the center of the NGC 346 star cluster,
indicating a segregation of the most massive stars. This segregation is likely
primordial considering the young age (~3 Myr) of NGC346, and its clumpy
structure which suggests that the cluster has likely not had sufficient time to
relax. Comparing our results for NGC346 with those derived for other star
clusters in the SMC and the Milky Way (MW), we conclude that, while the star
formation process might depend on the local cloud conditions, the IMF does not
seem to be affected by general environmental effects such as galaxy type,
metallicity, and dust content.Comment: 26 pages, 7 figures, 1 table, accepted for publication in A
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