78 research outputs found
A Physical Model for z~2 Dust Obscured Galaxies
We present a physical model for the origin of z~2 Dust-Obscured Galaxies
(DOGs), a class of high-redshift ULIRGs selected at 24 micron which are
particularly optically faint (24/R>1000). By combining N-body/SPH simulations
of high redshift galaxy evolution with 3D polychromatic dust radiative transfer
models, we find that luminous DOGs (with F24 > 0.3 mJy at z~2 are well-modeled
as extreme gas-rich mergers in massive (~5x10^12-10^13 Msun) halos, with
elevated star formation rates (~500-1000 Msun/yr) and/or significant AGN growth
(Mdot > 0.5 Msun/yr), whereas less luminous DOGs are more diverse in nature. At
final coalescence, merger-driven DOGs transition from being starburst dominated
to AGN dominated, evolving from a "bump" to a power-law shaped mid-IR (IRAC)
spectral energy distribution (SED). After the DOG phase, the galaxy settles
back to exhibiting a "bump" SED with bluer colors and lower star formation
rates. While canonically power-law galaxies are associated with being
AGN-dominated, we find that the power-law mid-IR SED can owe both to direct AGN
contribution, as well as to a heavily dust obscured stellar bump at times that
the galaxy is starburst dominated. Thus power-law galaxies can be either
starburst or AGN dominated. Less luminous DOGs can be well-represented either
by mergers, or by massive ($M_{\rm baryon} ~5x10^11 Msun) secularly evolving
gas-rich disc galaxies (with SFR > 50 Msun/yr). By utilising similar models as
those employed in the SMG formation study of Narayanan et al. (2010), we
investigate the connection between DOGs and SMGs. We find that the most heavily
star-forming merger driven DOGs can be selected as Submillimetre Galaxies
(SMGs), while both merger-driven and secularly evolving DOGs typically satisfy
the BzK selection criteria.Comment: Accepted by MNRAS; major changes include better description of
dependency on ISM specification and updated models allowing dust to evolve
with metallicity
Probing the Star Formation History and Initial Mass Function of the z~2.5 Lensed Galaxy SMM J163554.2+661225 with Herschel
We present the analysis of Herschel SPIRE far-infrared (FIR) observations of
the z = 2.515 lensed galaxy SMM J163554.2+661225. Combining new 250, 350, and
500 micron observations with existing data, we make an improved fit to the FIR
spectral energy distribution (SED) of this galaxy. We find a total infrared
(IR) luminosity of L(8--1000 micron) = 6.9 +/- 0.6x10^11 Lsol; a factor of 3
more precise over previous L_IR estimates for this galaxy, and one of the most
accurate measurements for any galaxy at these redshifts. This FIR luminosity
implies an unlensed star formation rate (SFR) for this galaxy of 119 +/- 10
Msol per yr, which is a factor of 1.9 +/- 0.35 lower than the SFR derived from
the nebular Pa-alpha emission line (a 2.5-sigma discrepancy). Both SFR
indicators assume identical Salpeter initial mass functions (IMF) with slope
Gamma=2.35 over a mass range of 0.1 - 100 Msol, thus this discrepancy suggests
that more ionizing photons may be necessary to account for the higher
Pa-alpha-derived SFR. We examine a number of scenarios and find that the
observations can be explained with a varying star formation history (SFH) due
to an increasing star formation rate (SFR), paired with a slight flattening of
the IMF. If the SFR is constant in time, then larger changes need to be made to
the IMF by either increasing the upper-mass cutoff to ~ 200 Msol, or a
flattening of the IMF slope to 1.9 +/- 0.15, or a combination of the two. These
scenarios result in up to double the number of stars with masses above 20 Msol,
which produce the requisite increase in ionizing photons over a Salpeter IMF
with a constant SFH.Comment: 9 pages, 4 figures, 1 table; Accepted for publication in the
Astrophysical Journa
Genomic, Pathway Network, and Immunologic Features Distinguishing Squamous Carcinomas
This integrated, multiplatform PanCancer Atlas study co-mapped and identified distinguishing
molecular features of squamous cell carcinomas (SCCs) from five sites associated with smokin
Pan-Cancer Analysis of lncRNA Regulation Supports Their Targeting of Cancer Genes in Each Tumor Context
Long noncoding RNAs (lncRNAs) are commonly dys-regulated in tumors, but only a handful are known toplay pathophysiological roles in cancer. We inferredlncRNAs that dysregulate cancer pathways, onco-genes, and tumor suppressors (cancer genes) bymodeling their effects on the activity of transcriptionfactors, RNA-binding proteins, and microRNAs in5,185 TCGA tumors and 1,019 ENCODE assays.Our predictions included hundreds of candidateonco- and tumor-suppressor lncRNAs (cancerlncRNAs) whose somatic alterations account for thedysregulation of dozens of cancer genes and path-ways in each of 14 tumor contexts. To demonstrateproof of concept, we showed that perturbations tar-geting OIP5-AS1 (an inferred tumor suppressor) andTUG1 and WT1-AS (inferred onco-lncRNAs) dysre-gulated cancer genes and altered proliferation ofbreast and gynecologic cancer cells. Our analysis in-dicates that, although most lncRNAs are dysregu-lated in a tumor-specific manner, some, includingOIP5-AS1, TUG1, NEAT1, MEG3, and TSIX, synergis-tically dysregulate cancer pathways in multiple tumorcontexts
Spatial Organization and Molecular Correlation of Tumor-Infiltrating Lymphocytes Using Deep Learning on Pathology Images
Beyond sample curation and basic pathologic characterization, the digitized H&E-stained images
of TCGA samples remain underutilized. To highlight this resource, we present mappings of tumorinfiltrating lymphocytes (TILs) based on H&E images from 13 TCGA tumor types. These TIL
maps are derived through computational staining using a convolutional neural network trained to
classify patches of images. Affinity propagation revealed local spatial structure in TIL patterns and
correlation with overall survival. TIL map structural patterns were grouped using standard
histopathological parameters. These patterns are enriched in particular T cell subpopulations
derived from molecular measures. TIL densities and spatial structure were differentially enriched
among tumor types, immune subtypes, and tumor molecular subtypes, implying that spatial
infiltrate state could reflect particular tumor cell aberration states. Obtaining spatial lymphocytic
patterns linked to the rich genomic characterization of TCGA samples demonstrates one use for
the TCGA image archives with insights into the tumor-immune microenvironment
Pan-cancer Alterations of the MYC Oncogene and Its Proximal Network across the Cancer Genome Atlas
Although theMYConcogene has been implicated incancer, a systematic assessment of alterations ofMYC, related transcription factors, and co-regulatoryproteins, forming the proximal MYC network (PMN),across human cancers is lacking. Using computa-tional approaches, we define genomic and proteo-mic features associated with MYC and the PMNacross the 33 cancers of The Cancer Genome Atlas.Pan-cancer, 28% of all samples had at least one ofthe MYC paralogs amplified. In contrast, the MYCantagonists MGA and MNT were the most frequentlymutated or deleted members, proposing a roleas tumor suppressors.MYCalterations were mutu-ally exclusive withPIK3CA,PTEN,APC,orBRAFalterations, suggesting that MYC is a distinct onco-genic driver. Expression analysis revealed MYC-associated pathways in tumor subtypes, such asimmune response and growth factor signaling; chro-matin, translation, and DNA replication/repair wereconserved pan-cancer. This analysis reveals insightsinto MYC biology and is a reference for biomarkersand therapeutics for cancers with alterations ofMYC or the PMN
Physical properties of dense molecular gas in centres of Seyfert galaxies
We present new ~1" resolution data of the dense molecular gas in the central
50-100 pc of four nearby Seyfert galaxies. PdBI observations of HCN and, in 2
of the 4 sources, simultaneously HCO+ allow us to carefully constrain the
dynamical state of the dense gas surrounding the AGN. Analysis of the
kinematics shows large line widths of 100-200 km/s FWHM that can only partially
arise from beam smearing of the velocity gradient. The observed morphological
and kinematic parameters (dimensions, major axis position angle, red and blue
channel separation, and integrated line width) are well reproduced by a thick
disk, where the emitting dense gas has a large intrinsic dispersion (20-40
km/s), implying that it exists at significant scale heights (25-30% of the disk
radius). To put the observed kinematics in the context of the starburst and AGN
evolution, we estimate the Toomre Q parameter. We find this is always greater
than the critical value, i.e. Q is above the limit such that the gas is stable
against rapid star formation. This is supported by the lack of direct evidence,
in these 4 Seyfert galaxies, for on-going star formation close around the AGN.
Instead, any current star formation tends to be located in a circumnuclear
ring. We conclude that the physical conditions are indeed not suited to star
formation within the central ~100 pc.Comment: 15 pages, 13 figures, 7 tables. Accepted for pubblication in MNRA
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