Fire in the Heart: A Characterization of the High Kinetic Temperatures and Heating Sources in the Nucleus of NGC253

The nuclear starburst within the central $\sim 15^{\prime\prime}$ ($\sim 250$ pc; $1^{\prime\prime} \simeq 17$ pc) of NGC253 has been extensively studied as a prototype for the starburst phase in galactic evolution. Atacama Large Millimeter/submillimeter Array (ALMA) imaging within receiver Bands 6 and 7 have been used to investigate the dense gas structure, kinetic temperature, and heating processes which drive the NGC253 starburst. Twenty-nine transitions from fifteen molecular species/isotopologues have been identified and imaged at $1.^{\prime\prime}5$ to $0.^{\prime\prime}4$ resolution, allowing for the identification of five of the previously-studied giant molecular clouds (GMCs) within the central molecular zone (CMZ) of NGC253. Ten transitions from the formaldehyde (H$_2$CO) molecule have been used to derive the kinetic temperature within the $\sim 0.^{\prime\prime}5$ to $5^{\prime\prime}$ dense-gas structures imaged. On $\sim 5^{\prime\prime}$ scales we measure $T_K \gtrsim 50$ K, while on size scales $\lesssim 1^{\prime\prime}$ we measure $T_K \gtrsim 300$ K. These kinetic temperature measurements further delineate the association between potential sources of dense gas heating. We have investigated potential heating sources by comparing our measurements to models which predict the physical conditions associated with dense molecular clouds that possess a variety of heating mechanisms. This comparison has been supplemented with tracers of recently-formed massive stars (Br$\gamma$) and shocks ([FeII]). Derived molecular column densities point to a radially-decreasing abundance of molecules with sensitivity to cosmic ray and mechanical heating within the NGC253 CMZ. These measurements are consistent with radio spectral index calculations which suggest a higher concentration of cosmic ray producing supernova remnants within the central 10 pc of NGC253.Comment: 60 pages, 25 figures (whew!), Accepted for publication in ApJ, Latest version includes minor corrections following proof submissio

1906 Expressing Disaster in Games

1906 is a serious first-person exploration game designed to increase the salience of a user\u27s own mortality while providing an engaging rendition of historical events. The game is set in San Francisco during the Great Earthquake and Fire Disaster of 1906, one of the most devastating natural disasters of our nation\u27s history. Players will have to interact with virtual citizens as well as try to keep their virtual self alive. Using its unique ambience and setting, 1906 allows players to experience life in the aftermath of one of America\u27s greatest natural disasters

The Bolocam Galactic Plane Survey. XIV. Physical Properties of Massive Starless and Star Forming Clumps

We sort $4683$ molecular clouds between $10^\circ< \ell <65^\circ$ from the Bolocam Galactic Plane Survey based on observational diagnostics of star formation activity: compact $70$ $\mu{\rm m}$ sources, mid-IR color-selected YSOs, ${\rm H_2O}$ and ${\rm CH_3OH}$ masers, and UCHII regions. We also present a combined ${\rm NH_3}$-derived gas kinetic temperature and ${\rm H_2O}$ maser catalog for $1788$ clumps from our own GBT 100m observations and from the literature. We identify a subsample of $2223$ ($47.5\%$) starless clump candidates, the largest and most robust sample identified from a blind survey to date. Distributions of flux density, flux concentration, solid angle, kinetic temperature, column density, radius, and mass show strong ($>1$ dex) progressions when sorted by star formation indicator. The median starless clump candidate is marginally sub-virial ($\alpha \sim 0.7$) with $>75\%$ of clumps with known distance being gravitationally bound ($\alpha < 2$). These samples show a statistically significant increase in the median clump mass of $\Delta M \sim 170-370$ M$_\odot$ from the starless candidates to clumps associated with protostars. This trend could be due to (i) mass growth of the clumps at $\dot{M}\sim200-440$ Msun Myr$^{-1}$ for an average free-fall $0.8$ Myr time-scale, (ii) a systematic factor of two increase in dust opacity from starless to protostellar phases, (iii) and/or a variation in the ratio of starless to protostellar clump lifetime that scales as $\sim M^{-0.4}$. By comparing to the observed number of ${\rm CH_3OH}$ maser containing clumps we estimate the phase-lifetime of massive ($M>10^3$ M$_\odot$) starless clumps to be $0.37 \pm 0.08 \ {\rm Myr} \ (M/10^3 \ {\rm M}_\odot)^{-1}$; the majority ($M<450$ M$_\odot$) have phase-lifetimes longer than their average free-fall time.Comment: Accepted for publication in ApJ; 33 pages; 22 figures; 7 table

Outflows and Massive Stars in the protocluster IRAS 05358+3543

We present new near-IR H2, CO J=2-1, and CO J = 3-2 observations to study outflows in the massive star forming region IRAS 05358+3543. The Canada-France-Hawaii Telescope H2 images and James Clerk Maxwell Telescope CO data cubes of the IRAS 05358 region reveal several new outflows, most of which emerge from the dense cluster of sub-mm cores associated with the Sh 2-233IR NE cluster to the northeast of IRAS 05358. We used Apache Point Observatory (APO) JHK spectra to determine line of sight velocities of the outflowing material. Analysis of archival VLA cm continuum data and previously published VLBI observations reveal a massive star binary as a probable source of one or two of the outflows. We have identified probable sources for 6 outflows and candidate counterflows for 7 out of a total of 11 seen to be originating from the IRAS 05358 clusters. We classify the clumps within Sh 2-233IR NE as an early protocluster and Sh 2-233IR SW as a young cluster, and conclude that the outflow energy injection rate approximately matches the turbulent decay rate in Sh 2-233IR NE.Comment: 15 figures, 42 pages, accepted for publication in the Astrophysical Journal. Full size figures are included at http://casa.colorado.edu/~ginsbura/iras05358.htm. Data can be accessed from figshare: http://figshare.com/articles/IRAS_05358_3543_Data_Cubes/80631

The Green Bank Ammonia Survey (GAS): First Results of NH3 mapping the Gould Belt

We present an overview of the first data release (DR1) and first-look science from the Green Bank Ammonia Survey (GAS). GAS is a Large Program at the Green Bank Telescope to map all Gould Belt star-forming regions with $A_V \gtrsim 7$ mag visible from the northern hemisphere in emission from NH$_3$ and other key molecular tracers. This first release includes the data for four regions in Gould Belt clouds: B18 in Taurus, NGC 1333 in Perseus, L1688 in Ophiuchus, and Orion A North in Orion. We compare the NH$_3$ emission to dust continuum emission from Herschel, and find that the two tracers correspond closely. NH$_3$ is present in over 60\% of lines-of-sight with $A_V \gtrsim 7$ mag in three of the four DR1 regions, in agreement with expectations from previous observations. The sole exception is B18, where NH$_3$ is detected toward ~ 40\% of lines-of-sight with $A_V \gtrsim 7$ mag. Moreover, we find that the NH$_3$ emission is generally extended beyond the typical 0.1 pc length scales of dense cores. We produce maps of the gas kinematics, temperature, and NH$_3$ column densities through forward modeling of the hyperfine structure of the NH$_3$ (1,1) and (2,2) lines. We show that the NH$_3$ velocity dispersion, ${\sigma}_v$, and gas kinetic temperature, $T_K$, vary systematically between the regions included in this release, with an increase in both the mean value and spread of ${\sigma}_v$ and $T_K$ with increasing star formation activity. The data presented in this paper are publicly available.Comment: 33 pages, 27 figures, accepted to ApJS. Datasets are publicly available: https://dataverse.harvard.edu/dataverse/GAS_DR

Super Star Clusters in the Central Starburst of NGC 4945

The nearby (3.8Mpc) galaxy NGC 4945 hosts a nuclear starburst and Seyfert type 2 active galactic nucleus (AGN). We use the Atacama Large Millimeter/submillimeter Array (ALMA) to image the 93 GHz (3.2 mm) free-free continuum and hydrogen recombination line emission (H40 alpha and H42 alpha) at 2.2 pc (0 12) resolution. Our observations reveal 27 bright, compact sources with FWHM sizes of 1.4-4.0 pc, which we identify as candidate super star clusters. Recombination line emission, tracing the ionizing photon rate of the candidate clusters, is detected in 15 sources, six of which have a significant synchrotron component to the 93 GHz continuum. Adopting an age of similar to 5Myr, the stellar masses implied by the ionizing photon luminosities are log(10) (M*/M-circle dot) approximate to 4.7-6.1. We fit a slope to the cluster mass distribution and find beta = -1.8 +/-.0.4. The gas masses associated with these clusters, derived from the dust continuum at 350 GHz, are typically an order of magnitude lower than the stellar mass. These candidate clusters appear to have already converted a large fraction of their dense natal material into stars and, given their small freefall times of similar to 0.05 Myr, are surviving an early volatile phase. We identify a pointlike source in 93 GHz continuum emission that is presumed to be the AGN. We do not detect recombination line emission from the AGN and place an upper limit on the ionizing photons that leak into the starburst region of Q(0).&lt;.10(52) s(-1)

Droplets I: Pressure-Dominated Sub-0.1 pc Coherent Structures in L1688 and B18

We present the observation and analysis of newly discovered coherent structures in the L1688 region of Ophiuchus and the B18 region of Taurus. Using data from the Green Bank Ammonia Survey (GAS), we identify regions of high density and near-constant, almost-thermal, velocity dispersion. Eighteen coherent structures are revealed, twelve in L1688 and six in B18, each of which shows a sharp "transition to coherence" in velocity dispersion around its periphery. The identification of these structures provides a chance to study the coherent structures in molecular clouds statistically. The identified coherent structures have a typical radius of 0.04 pc and a typical mass of 0.4 Msun, generally smaller than previously known coherent cores identified by Goodman et al. (1998), Caselli et al. (2002), and Pineda et al. (2010). We call these structures "droplets." We find that unlike previously known coherent cores, these structures are not virially bound by self-gravity and are instead predominantly confined by ambient pressure. The droplets have density profiles shallower than a critical Bonnor-Ebert sphere, and they have a velocity (VLSR) distribution consistent with the dense gas motions traced by NH3 emission. These results point to a potential formation mechanism through pressure compression and turbulent processes in the dense gas. We present a comparison with a magnetohydrodynamic simulation of a star-forming region, and we speculate on the relationship of droplets with larger, gravitationally bound coherent cores, as well as on the role that droplets and other coherent structures play in the star formation process.Comment: Accepted by ApJ in April, 201