We present Spitzer 3.6, 4.5, 5.8, 8.0, and 24 mu m images of the Mon OB1 East giant molecular cloud, which contains the young star forming region NGC 2264, as well as more extended star formation. ...With Spitzer data and Two Micron All Sky Survey photometry, we identify and classify young stellar objects (YSOs) with dusty circumstellar disks and/or envelopes in Mon OB1 East by their infrared-excess emission and study their distribution with respect to cloud material. We find a correlation between the local surface density of YSOs and column density of molecular gas as traced by dust extinction that is roughly described as a power law in these quantities. NGC 2264 follows a power-law index of ~2.7, exhibiting a large YSO surface density for a given gas column density. Outside of NGC 2264 where the surface density of YSOs is lower, the power law is shallower and the region exhibits a larger gas column density for a YSO surface density, suggesting the star formation is more recent. In order to measure the fraction of cloud members with circumstellar disks/envelopes, we estimate the number of diskless pre-main-sequence stars by statistical removal of background star detections. We find that the disk fraction of the NGC 2264 region is 45%, while the surrounding, more distributed regions show a disk fraction of 19%. This may be explained by the presence of an older, more dispersed population of stars. In total, the Spitzer observations provide evidence for heterogenous, non-coeval star formation throughout the Mon OB1 cloud.
We report on the lambda = 5-36 mu m Spitzer Infrared Spectrograph (IRS) spectra of 79 young stellar objects in the very young nearby cluster NGC 1333. NGC 1333's youth enables the study of early ...protoplanetary disk properties, such as the degree of settling and the formation of gaps and clearings. We construct spectral energy distributions (SEDs) using our IRS data as well as published photometry and classify our sample into SED classes. Using "extinction-free" spectral indices, we determine whether the disk, envelope, or photosphere dominates the spectrum. We analyze the dereddened spectra of objects that show disk-dominated emission using spectral indices and properties of silicate features in order to study the vertical and radial structure of protoplanetary disks in NGC 1333. At least nine objects in our sample of NGC 1333 show signs of large (several AU) radial gaps or clearings in their inner disk. Disks with radial gaps in NGC 1333 show more nearly pristine silicate dust than their radially continuous counterparts. We compare properties of disks in NGC 1333 to those in three other well-studied regions, Taurus-Auriga, Ophiuchus, and Chamaeleon I, and find no difference in their degree of sedimentation and dust processing.
We present an overview of the initial results from the Chandra Planetary Nebula Survey (CHANPLANS), the first systematic (volume-limited) Chandra X-Ray Observatory survey of planetary nebulae (PNe) ...in the solar neighborhood. The first phase of CHANPLANS targeted 21 mostly high-excitation PNe within ~1.5 kpc of Earth, yielding four detections of diffuse X-ray emission and nine detections of X-ray-luminous point sources at the central stars (CSPNe) of these objects. Combining these results with those obtained from Chandra archival data for all (14) other PNe within ~1.5 kpc that have been observed to date, we find an overall X-ray detection rate of ~70% for the 35 sample objects. Roughly 50% of the PNe observed by Chandra harbor X-ray-luminous CSPNe, while soft, diffuse X-ray emission tracing shocks-in most cases, "hot bubbles"-formed by energetic wind collisions is detected in ~30%; five objects display both diffuse and point-like emission components. The presence (or absence) of X-ray sources appears correlated with PN density structure, in that molecule-poor, elliptical nebulae are more likely to display X-ray emission (either point-like or diffuse) than molecule-rich, bipolar, or Ring-like nebulae. All but one of the point-like CSPNe X-ray sources display X-ray speetta that are harder than expected from hot (~100 kK) central stars emitting as simple blackbodies; the lone apparent exception is the central star of the Dumbbell nebula, NGC 6853. These hard X-ray excesses may suggest a high frequency of binary companions to CSPNe. Other potential explanations include self-shocking winds or PN mass fallback. Most PNe detected as diffuse X-ray sources are elliptical nebulae that display a nested shell/halo structure and bright ansae; the diffuse X-ray emission regions are confined within inner, sharp-rimmed shells. All sample PNe that display diffuse X-ray emission have inner shell dynamical ages lap5 x 10 super(3) yr, placing firm constraints on the timescale for strong shocks due to wind interactions in PNe. The high-energy emission arising in such wind shocks may contribute to the high excitation states of certain archetypical "hot bubble" nebulae (e.g., NGC 2392, 3242, 6826, and 7009).
Melbourne 2030 Birrell, Bob; Healy, Ernest; O'Connor, Kevin
2005
eBook
The Melbourne 2030 plan is the Victorian Government's blueprint for the accommodation of an additional one million people in Melbourne by 2030. The plan seeks to change the shape of Melbourne ...radically. The vision is of a compact city in which growth will be concentrated in existing commercial centres (activity centres). Notwithstanding this fundamental departure from the low density pattern of the past, it is claimed that Melbourne's famed 'liveability' will be preserved. This book explores: the intellectual origins of the plan, the demographic assumptions behind it, the mode of implementation, the likely impact on the built environment, the environmental and social consequences, the heritage outcomes and alternative planning options. It critically examines assumptions about the projected demand for higher density housing, and argues that the plan's 'compact city' vision is unlikely to be achieved because it fails to come to grips with the economic and demographic realities facing Melbourne.
"There has been much concern about the level of social welfare payments reputedly received by New Zealanders in Australia. Analysis of these payments shows that the recent renegotiation of the ...Australia and New Zealand Social Security Agreement will shift much of the financial burden to the New Zealand Government. Recent migration patterns show increasing shares of non-New Zealand-born persons and older persons amongst the New Zealand citizens arriving in Australia."
"Analysis of data from the 1996 Census of six Melbourne localities suggests that some recent explanations for spatial concentrations of the poor in metropolitan areas are incomplete. In these ...middle-suburban locations the better-off are moving out, leaving behind those with less resources. While people of Australian or English-speaking background are more likely than those of non-English-speaking background (NESB) to leave, the inflow from overseas is predominantly of poor NESB people. Together, these two processes are adding to the spatial concentrations of the poor in Melbourne."
"Despite the recovery in the Australian economy since 1991, the number of poor families in Australia has continued to increase. By September 1996, 43 per cent of Australian families could be regarded ...as poor. Some four out of every ten of these were headed by lone parents. These findings highlight major questions about the resources available to poor families in a context where families are increasingly expected to invest heavily in their children's education."
We report on the {\lambda} = 5-36{\mu}m Spitzer Infrared Spectrograph spectra of 79 young stellar objects in the very young nearby cluster NGC 1333. NGC 1333's youth enables the study of early ...protoplanetary disk properties, such as the degree of settling as well as the formation of gaps and clearings. We construct spectral energy distributions (SEDs) using our IRS data as well as published photometry and classify our sample into SED classes. Using "extinction-free" spectral indices, we determine whether the disk, envelope, or photosphere dominates the spectrum. We analyze the dereddened spectra of objects which show disk dominated emission using spectral indices and properties of silicate features in order to study the vertical and radial structure of protoplanetary disks in NGC 1333. At least nine objects in our sample of NGC 1333 show signs of large (several AU) radial gaps or clearings in their inner disk. Disks with radial gaps in NGC 1333 show more-nearly pristine silicate dust than their radially continuous counterparts. We compare properties of disks in NGC 1333 to those in three other well studied regions, Taurus-Auriga, Ophiuchus and Chamaeleon I, and find no difference in their degree of sedimentation and dust processing.
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