Browsing by Subject "galaxies : high-redshift"

Now showing 1 - 3 of 3

The First Supernova Explosions: Energetics, Feedback, And Chemical Enrichment
(2007-11) Greif, Thomas H.; Johnson, Jarrett L.; Bromm, Volker; Klessen, Ralf S.; Greif, Thomas H.; Johnson, Jarrett L.; Bromm, Volker
We perform three-dimensional smoothed particle hydrodynamics simulations in a realistic cosmological setting to investigate the expansion, feedback, and chemical enrichment properties of a 200M(circle dot) pair-instability supernova in the high-redshift universe. We find that the SN remnant propagates for a Hubble time at z similar or equal to 20 to a final mass-weighted mean shock radius of 2.5 kpc (proper), roughly half the size of the H II region, and in this process sweeps up a total gas mass of 2: 5; 10(5) M-circle dot. The morphology of the shock becomes highly anisotropic once it leaves the host halo and encounters filaments and neighboring minihalos, while the bulk of the shock propagates into the voids of the intergalactic medium. The SN entirely disrupts the host halo and terminates further star formation for at least 200 Myr, while in our specific case it exerts positive mechanical feedback on neighboring minihalos by shock-compressing their cores. In contrast, we do not observe secondary star formation in the dense shell via gravitational fragmentation, due to the previous photoheating by the progenitor star. We find that cooling by metal lines is unimportant for the entire evolution of the SN remnant, while the metal-enriched, interior bubble expands adiabatically into the cavities created by the shock, and ultimately into the voids with a maximum extent similar to the final mass-weighted mean shock radius. Finally, we conclude that dark matter halos of at least M-vir greater than or similar to 10(8) M-circle dot must be assembled to recollect all components of the swept-up gas.
The Multiwavelength Survey By Yale-Chile (MUSYC) Wide K-Band Imaging, Photometric Catalogs, Clustering, And Physical Properties Of Galaxies At Z Similar To 2
(2008-07) Blanc, Guillermo A.; Lira, Paulina; Barrientos, L. Felipe; Aguirre, Paula; Francke, Harod; Taylor, Edward N.; Quadri, Ryan; Marchesini, Danilo; Infante, Leopoldo; Gawiser, Eric; Hall, Patrick B.; Willis, Jon P.; Herrera, David; Maza, Jose; Blanc, Guillermo A.
We present K-band imaging of two similar to 30' x 30' fields covered by the Multiwavelength Survey by Yale-Chile (MUSYC) Wide NIR Survey. The SDSS 1030+05 and Cast 1255 fields were imaged with the Infrared Side Port Imager (ISPI) on the 4 m Blanco telescope at the Cerro Tololo Inter-American Observatory (CTIO) to a 5 sigma point-source limiting depth of K similar to 20 (Vega). Combining these data with the MUSYC optical UBVRIz imaging, we created multiband K-selected source catalogs for both fields. These catalogs, together with the MUSYC K-band catalog of the Extended Chandra Deep Field South (ECDF-S) field, were used to select K 20 BzK galaxies over an area of 0.71 deg(2). This is the largest area ever surveyed for BzK galaxies. We present number counts, redshift distributions, and stellar masses for our sample of 3261 BzK galaxies (2502 star-forming [sBzK] and 759 passively evolving [pBzK]), as well as reddening and star formation rate estimates for the star-forming BzK systems. We also present two-point angular correlation functions and spatial correlation lengths for both sBzK and pBzK galaxies and show that previous estimates of the correlation function of these galaxies were affected by cosmic variance due to the small areas surveyed. We have measured correlation lengths r(0) of 8.89 +/- 2.03 and 10.82 +/- 1.72 Mpc for sBzK and pBzK galaxies, respectively. This is the first reported measurement of the spatial correlation function of passive BzK galaxies. In the Lambda CDM scenario of galaxy formation, these correlation lengths at z similar to 2 translate into minimum masses of similar to 4 x 10(12) and similar to 9 x 10(12) M(circle dot) for the dark matter halos hosting sBzK and pBzK galaxies, respectively. The clustering properties of the galaxies in our sample are consistent with their being the descendants of bright Lyman break galaxies at z similar to 3, and the progenitors of present-day > 1L* galaxies.
Uncovering The Chemical Signature Of The First Stars In The Universe
(2008-05) Karlsson, Torgny; Johnson, Jarrett L.; Bromm, Volker; Johnson, Jarrett L.; Bromm, Volker
The chemical abundance patterns observed in metal-poor Galactic halo stars contain the signature of the first supernovae, and thus allow us to probe the first stars that formed in the universe. We construct a theoretical model for the early chemical enrichment history of the Milky Way, aiming in particular at the contribution from pair-instability supernovae (PISNe). These are a natural consequence of current theoretical models for primordial star formation at the highest masses. However, no metal-poor star displaying the distinct PISN signature has yet been observed. We here argue that this apparent absence of any PISN signature is due to an observational selection effect. Whereas most surveys traditionally focus on the most metal-poor stars, we predict that early PISN enrichment tends to "overshoot,'' reaching enrichment levels of [Ca/H] similar or equal to -2.5 that would be missed by current searches. We utilize existing observational data to place constraints on the primordial initial mass function (IMF). The number fraction of PISNe in the primordial stellar population is estimated to be < 0.07, or <= 40% by mass, assuming that metal-free stars have masses in excess of 10 M-circle dot. We further predict, based on theoretical estimates for the relative number of PISNe, that the expected fraction of second-generation stars below [Ca/H] = -2 with a dominant (i. e., > 90%) contribution from PISNe is merely similar to 10(-4) to 5 x 10(-4). The corresponding fraction of stars formed from gas exclusively enriched by PISNe is a factor of similar to 4 smaller. With the advent of next-generation telescopes and new, deeper surveys, we should be able to test these predictions.