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Gamma-ray bursts are the most luminous objects known: they outshine their host galaxies making them ideal candidates for probing large-scale structure. Earlier it has been found that the angular distribution of different groups of GRBs (long, intermediate and short) show deviation from the full randomness at different levels (e.g. Vavrek et al. (2008)).
In the current sample there are more than 361 GRBs with position and redshift: the large scale homogeneous and isotropic distribution were checked with nearest-neighbour tests and with the two-point correlation function.
This work sketches how SDSS ugr colors and Kepler 2 in halo fields can identify red giants 50 – 100 kpc distant with minimal metallicity bias. For these mildly-reddened, metal-poor giants, (g-r)o yields the effective temperature Teff to 100 K. K2 can detect the p-mode oscillations of red giants and measure their frequency of maximum power νmax. This sets the luminosity Lbol and thus the distance, plus an estimate of metallicity [Fe/H].
The availability of high spatial resolution molecular gas observations from ALMA, and similar resolution observations in the radio continuum using the VLA, is providing the opportunity to make comparisons with specific features seen in optical observations more directly than in the past. Using our ALMA observations of the Antennae galaxies as a springboard, we have compared the locations of small-scale CO (3−2) features with a variety of multi-wavelength observations, in particular optical and near-infrared imaging using both broad (UBVI) and narrow-band data (Hα and Paβ) taken with the HST, and radio (3.6 cm) continuum observations taken with the VLA. This comparison leads to the development of an evolutionary classification system which provides a framework for studying the sequence of star cluster formation and evolution, from diffuse Giant Molecular Clouds (GMCs), to proto, embedded, emerging, young, and intermediate/old star clusters. Using this evolutionary framework, we estimate the maximum age range of clusters formed in a single GMC is approximately 10 Myr. This suggests that the molecular gas is removed over this timescale, resulting in the cessation of star formation and the destruction of the GMC within a radius of about 200 pc.
FeLoBAL quasars may be an early evolutionary stage of merger-triggered quasar activity. We test this hypothesis using HST imaging of four FeLoBAL quasars. The host galaxy colors are consistent with early-type quiescent galaxies or heavily-obscured starbursts.
Characterization of the binary fractions in star clusters is of fundamental importance for many fields in astrophysics. Observations indicate that the majority of stars are found in binary systems, while most stars with masses greater than 0.5M⊙ are formed in star clusters. In addition, since binaries are on average more massive than single stars, in resolved star clusters these systems are thought to be good tracers of (dynamical) mass segregation. Over time, dynamical evolution through two-body relaxation will cause the most massive objects to migrate to the cluster center, while the relatively lower-mass objects remain in or migrate to orbits at greater radii. This process will globally dominate a cluster’s stellar distribution. However, close encounters involving binary systems may disrupt ‘soft’ binaries. This process will occur more frequently in a cluster’s central, dense region than in its periphery, which may mask the effects of mass segregation. Using high resolution Hubble Space Telescope observations, combined with sophisticated N-body simulations, we investigate the radial distributions of the main-sequence binary fractions in massive young Large Magellanic Cloud star clusters. We show that binary disruption may play an important role on very short timescales, depending on the environmental conditions in the cluster cores. This may lead to radial binary fractions that initially decline in the cluster centers, which is contrary to the effects expected from dynamical mass segregation.
Jupiter-sized brown dwarfs are found in the solar neighborhood with effective temperature Teff as low as 250 K [1]. Iron, silicates, chlorides and sulfides condense in the atmospheres of the Teff ≈ 2000 K L-type and Teff ≈ 1000 K T-type dwarfs [2]. At the T-/Y-type boundary, Teff ≈ 500 K and atmospheres are clear [3]. The next species to condense are H2O at Teff ≈ 350 K and NH3 at Teff ≈ 200 K [4].
The host galaxies of nearby (z<0.3) core-collapse supernovae and long-duration gamma-ray bursts offer an excellent means of probing the environments and populations that produce these events' varied massive progenitors. These same young stellar progenitors make LGRBs and SNe valuable and potentially powerful tracers of star formation, metallicity, the IMF, and the end phases of stellar evolution. However, properly utilizing these progenitors as tools requires a thorough understanding of their formation and, consequently, the physical properties of their parent host environments. In this talk I will review some of the recent work on LGRB and SN hosts with resolved environments that allows us to probe the precise explosion sites and surrounding environments of these events in incredible detail.
The Herschel Space Observatory was the fourth cornerstone mission in the European Space Agency (ESA) science programme with excellent broad band imaging capabilities in the sub-mm and far-infrared part of the spectrum. Although the spacecraft finished its observations in 2013, it left a large legacy dataset that is far from having been fully scrutinised and still has a large potential for new scientific discoveries. This is specifically true for the photometric observations of the PACS and SPIRE instruments. Some source catalogues have already been produced by individual observing programs, but there are many observations that risk to remain unexplored. To maximise the science return of the SPIRE and PACS data sets, we are in the process of building the Herschel Point Source Catalogue (HPSC) from all primary and parallel mode observations. Our homogeneous source extraction enables a systematic and unbiased comparison of sensitivity across the different Herschel fields that single programs will generally not be able to provide. The catalogue will be made available online through archives like the Herschel Science Archive (HSA), the Infrared Science Archive (IRSA), and the Strasbourg Astronomical Data Center (CDS).
We present the first measurement of the anisotropy parameter β using 3D kinematic information outside of the solar neighborhood. Our sample consists of 13 Milky Way halo stars with measured proper motions and radial velocities in the line of sight of M31. Proper motions were measured using deep, multi-epoch HST imaging, and radial velocities were measured from Keck II/DEIMOS spectra. We measure β = −0.3−0.9+0.4, which is consistent with isotropy, and inconsistent with measurements in the solar neighborhood. We suggest that this may be the kinematic signature of a relatively early, massive accretion event, or perhaps several such events.
Cold molecular and atomic gas plays a central role in our understanding of early galaxy formation and evolution. It represents the component of the interstellar medium (ISM) that stars form out of, and its mass, distribution, excitation, and dynamics provide crucial insight into the physical processes that support the ongoing star formation and stellar mass buildup. We here present results that demonstrate the capability of the Atacama Large (sub-)Millimeter Array (ALMA) to detect the cold ISM and dust in “normal” galaxies at redshifts z=5–6. We also show detailed studies of the ISM in massive, dust-obscured starburst galaxies out to z>6 with ALMA, the Combined Array for Research in Millimeter-wave Astronomy (CARMA), the Plateau de Bure Interferometer (PdBI), and the Karl G. Jansky Very Large Array (VLA). These observations place some of the most direct constraints on the dust-obscured fraction of the star formation history of the universe at z>5 to date, showing that “typical” galaxies at these epochs have low dust content, but also that highly-enriched, dusty starbursts already exist within the first billion years after the Big Bang.
This short review is intended to be a snapshot of some recent observational facts and open questions regarding the study of chemical evolution in the innermost regions of the Milky Way, as traced by spectroscopy of cool giant and supergiant stars.
Laboratory astrophysics is the Rosetta stone that enables astronomers to understand and interpret the cosmos. The IAU Commission 14, the predecessor of the new IAU Laboratory Astrophysics Commission C. B5 and the AAS Laboratory Astrophysics Division (LAD) decided to coordinate their efforts this summer to hold a joint meeting at the IAU General Assembly.
C46 was a Commission of the Executive Committee of the IAU under Division XII (Union-Wide Activities), then after 2012 under Division C (Education, Outreach, and Heritage). It was the only commission dealing exclusively with astronomy education; a previous Commission 38 (Exchange of Astronomers), which allocated travel grants to astronomers who needed them, and a Working Group on the Worldwide Development of Astronomy, have been absorbed by Commission 46.
Comparative analysis of GMS and MSC is presented based on data collected on these objects in the Galaxy and other galaxies. The model is proposed of gravitational instability of GMC and MSC system. Some implications are discussed.
The importance of dark sky protection, potential threats to further degradation from LED technology, the announcement of a new world atlas of artificial night sky brightness, and the use of color images from the orbiting International Space Station for monitoring potential sources of light pollution were discussed in the six talks of this session. It was clear from the presentations that the work of professional astronomy depends upon continued restraint in the use of outdoor lighting, especially new LED technology, which relies upon blue-rich sources to support the advantages of high luminous efficacy and resulting energy savings.
Dessart et al., demonstrated that type II supernova (SN II) model spectra present increasing metal line strength with increasing progenitor metallicity. To confront these models with observations, we obtained a large sample of SN II host H ii region emission line spectroscopy. We show that inferred SN II host H ii region metallicities have a statistically significant correlation with the strength of SN II metal lines, specifically Fe ii 5018Å.
One of the most powerful SOC tools - the wavelet transform modulus maxima approach to calculating multifractality - is connected to one of the most powerful equations in all of physics - Ampere's law. In doing so, the multifractal spectra can be expressed in terms of current density, and how current density can then be used for the prediction of future energy release from such a system.
When an area of education, and more particularly the research within this area, is aimed to development, one of the basic requirements is the existence of a regular publication that accounts for the scientific production in that area. This study aims to analyze 10 years of Latin-American Journal of Astronomy Education (RELEA) [http://www.relea.ufscar.br/].
N131 is an infrared dust bubble residing in a molecular filament. We aim to study the formation and fragmentation of this bubble with multi-wavelength dust and gas observations. Towards the bubble N131, we analyzed archival multi-wavelength observations including 3.6, 4.5, 5.8, 8.0, 24, 70, 160, 250, 350, 500 μm, 1.1 mm, and 21 cm. In addition, we performed new observations of CO (2-1), CO (1-0), and 13CO (1-0) with the IRAM 30-m telescope. Multi-wavelength dust and gas observations reveal a ringlike shell with compact fragments, two filamentary structures, and a secondary bubble N131-A. The bubble N131 is a rare object with a large hole at 24 μm and 21 cm in the direction of its center. The dust and gas clumps are compact and might have been compressed at the inner edge of the ringlike shell, while they are extended and might be pre-existing at the outer edge. The column density, excitation temperature, and velocity show a potentially hierarchical distribution from the inner to outer edge of the ringlike shell. We also detected the front and back sides of the secondary bubble N131-A in the direction of its center. The derived Lyman-continuum ionizing photon flux within N131-A is equivalent to an O9.5 star. Based on the above, we suggest that the bubble N131 might be triggered by the strong stellar winds from a group of massive stars inside the bubble. We propose a scenario in which the bubble N131 forms from the disruption of a gas filament by expansion of H II region, strong stellar winds, and fragments under self-gravity.
The spectrum of the Fe I atom is critical to many areas of astrophysics and beyond. Measurements of the energies of its high-lying levels remain seriously incomplete. Here we update the work by Peterson & Kurucz (2015) to identify such levels using new and archival high-resolution absorption-line UV and optical spectra of stars whose warm temperatures favor Fe I lines. Our GO-14161 Hubble program will obtain UV spectra for four metal-poor turnoff stars, archive them at ASTRAL, and draw from them the new identifications of 250 – 500 Fe I levels.