110 research outputs found
The 2009 National School Climate Survey: The Experiences of Lesbian, Gay, Bisexual and Transgender Youth in Our Nation's Schools
National survey of the school experiences of 7,261 lesbian, gay, bisexual and trasngender secondary school students.In our 2009 survey, we examine the experiences of LGBT students with regard to indicators of negative school climate:hearing biased remarks, including homophobic remarks, in school;feeling unsafe in school because of personal characteristics, such as sexual orientation, gender expression, or race/ethnicity;missing classes or days of school because of safety reasons; andexperiences of harassment and assault in school. We also examine the possible negative effects of a hostile school climate on LGBT students' academic achievement, educational aspirations, and psychological well-being. We explore the diverse nature of LGBT students' experiences by reporting on how these differ by students' personal and community characteristics. We also examine whether or not students report experiences of victimization to school officials or to family members and how these adults address the problem. In addition, we demonstrate the degree to which LGBT students have access to supportive resources in school, and we explore the possible benefits of these resources, including Gay-Straight Alliances (GSAs), school harassment/assault policies, supportive school staff, and curriculum that is inclusive of LGBT-related topics.Given that we now have 10 years of data, we examine changes over the past decade on both indicators of negative school climate and levels of access to LGBT-related resources in schools
Dynamics of the 6.7 and 12.2 GHz methanol masers around Cepheus A HW2
The 6.7 GHz methanol maser is exclusively associated with high-mass star
formation. However, it remains unclear what structures harbour the methanol
masers. Cepheus A is one of the closest regions of massive star formation,
making it an excellent candidate for detailed studies. We determine the
dynamics of maser spots in the high-mass star-forming region Cepheus A in order
to infer where and when the maser emission occurs. Very long baseline
interferometry (VLBI) observations of the 6.7 and 12.2 GHz methanol masers
allows for mapping their spatial and velocity distribution. Phase-referencing
is used to determine the astrometric positions of the maser emission, and
multi-epoch observations can reveal 3D motions. The 6.7 GHz methanol masers are
found in a filamentary structure over ~1350 AU, straddling the waist of the
radio jet HW2. The positions agree well with previous observations of both the
6.7 and 12.2 GHz methanol masers. The velocity field of the maser spots does
not show any sign of rotation, but is instead consistent with an infall
signature. The 12.2 GHz methanol masers are closely associated with the 6.7 GHz
methanol masers, and the parallax that we derive confirms previous
measurements. We show that the methanol maser emission very likely arises in a
shock interface in the equatorial region of Cepheus A HW2 and presents a model
in which the maser emission occurs between the infalling gas and the accretion
disk/process.Comment: 9 pages, 5 figures; accepted for publication in Astronomy and
Astrophysic
Magnetic field regulated infall on the disc around the massive protostar Cepheus A HW2
We present polarization observations of the 6.7-GHz methanol masers around
the massive protostar Cepheus A HW2 and its associated disc. The data were
taken with the Multi-Element Radio Linked Interferometer Network. The maser
polarization is used to determine the full three-dimensional magnetic field
structure around Cepheus A HW2. The observations suggest that the masers probe
the large scale magnetic field and not isolated pockets of a compressed field.
We find that the magnetic field is predominantly aligned along the protostellar
outflow and perpendicular to the molecular and dust disc. From the
three-dimensional magnetic field orientation and measurements of the magnetic
field strength along the line of sight, we are able to determine that the high
density material, in which the masers occurs, is threaded by a large scale
magnetic field of ~23 mG. This indicates that the protostellar environment at
~1000 AU from Cepheus A HW2 is slightly supercritical (lambda approximately
1.7) and the relation between density and magnetic field is consistent with
collapse along the magnetic field lines. Thus, the observations indicate that
the magnetic field likely regulates accretion onto the disc. The magnetic field
dominates the turbulent energies by approximately a factor of three and is
sufficiently strong to be the crucial component stabilizing the massive
accretion disc and sustaining the high accretion rates needed during massive
star-formation.Comment: 10 pages, 6 figures; accepted for publication in MNRAS. High
resolution version can be found at
http://www.astro.uni-bonn.de/~wouter/papers/papers.shtm
Spectrophotometric Distances to Galactic H\,{\sc{ii}} Regions
We present a near infrared study of the stellar content of 35 H\,{\sc{ii}}
regions in the Galactic plane. In this work, we have used the near infrared
domain , and band color images to visually inspect the
sample. Also, color-color and color-magnitude diagrams were used to indicate
ionizing star candidates, as well as, the presence of young stellar objects
such as classical TTauri Stars (CTTS) and massive young stellar objects
(MYSOs). We have obtained {\it Spitzer} IRAC images for each region to help
further characterize them. {\it Spitzer} and near infrared morphology to place
each cluster in an evolutionary phase of development. {\it Spitzer} photometry
was also used to classify the MYSOs. Comparison of the main sequence in
color-magnitude diagrams to each observed cluster was used to infer whether or
not the cluster kinematic distance is consistent with brightnesses of the
stellar sources. We find qualitative agreement for a dozen of the regions, but
about half the regions have near infrared photometry that suggests they may be
closer than the kinematic distance. A significant fraction of these already
have spectrophotometric parallaxes which support smaller distances. These
discrepancies between kinematic and spectrophotometric distances are not due to
the spectrophotometric methodologies, since independent non-kinematic
measurements are in agreement with the spectrophotometric results. For
instance, trigonometric parallaxes of star-forming regions were collected from
the literature and show the same effect of smaller distances when compared to
the kinematic results. In our sample of H\,{\sc{ii}} regions, most of the
clusters are evident in the near infrared images. Finally, it is possible to
distinguish among qualitative evolutionary stages for these objects.Comment: 59 pages, 146 figures and 4 tables. MNRAS accepte
A Keplerian disk with a four-arm spiral birthing an episodically accreting high-mass protostar
High-mass protostars (M⋆ > 8M⊙) are thought to gain the majority of their mass via short, intense bursts of growth. This episodic accretion is thought to be facilitated by gravitationally unstable and subsequently inhomogeneous accretion disks. Limitations of observational capabilities, paired with a lack of observed accretion burst events, have withheld affirmative confirmation of the association between disk accretion, instability and the accretion burst phenomenon in high-mass protostars. Following its 2019 accretion burst, a heatwave driven by a burst of radiation propagated outward from the high-mass protostar G358.93-0.03-MM1. Six very long baseline interferometry observations of the radiatively pumped 6.7 GHz methanol maser were conducted during this period, tracing ever increasing disk radii as the heatwave propagated outward. Concatenating the very long baseline interferometry maps provided a sparsely sampled, milliarcsecond view of the spatio-kinematics of the accretion disk covering a physical range of ~50–900 AU. We term this observational approach ‘heatwave mapping’. We report the discovery of a Keplerian accretion disk with a spatially resolved four-arm spiral pattern around G358.93-0.03-MM1. This result positively implicates disk accretion and spiral arm instabilities into the episodic accretion high-mass star formation paradigm
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