The Lyman Alpha Forest in Hierarchical Cosmologies

The comparison of quasar absorption spectra with numerically simulated spectra from hierarchical cosmological models of structure formation promises to be a valuable tool to discriminate among these models. We present simulation results for the column density, Doppler b parameter, and optical depth probability distributions for five popular cosmological models.Comment: 4 pages, 3 figures, uses aipproc.sty, to appear in the Proceedings of the 9th Annual October Astrophysics Conference in Maryland, "After the Dark Ages: When Galaxies Were Young (the Universe at 2<z<5)", ed. S. S. Holt and E. P. Smith, October 12-14, 199

Constraints on Mass Spectrum of Fourth Generation Fermions and Higgs Bosons

We reanalyze constraints on the mass spectrum of the chiral fourth generation fermions and the Higgs bosons for the standard model (SM4) and the two Higgs doublet model (THDM). We find that the Higgs mass in the SM4 should be larger than roughly the fourth generation up-type quark mass, while the light CP even Higgs mass in the THDM can be smaller. Various mass spectra of the fourth generation fermions and the Higgs bosons are allowed. The phenomenology of the fourth generation models is still rich.Comment: 15 pages, 16 figures; some points clarified, references added, to appear in Phys.Rev.

The infall of the Virgo elliptical galaxy M60 toward M87 and the gaseous structures produced by Kelvin-Helmholtz instabilities

We present Chandra observations of hot gas structures, characteristic of gas stripping during infall, in the Virgo cluster elliptical galaxy M60 (NGC4649) located 1 Mpc east of M87. 0.5−2 keV Chandra X-ray images show a sharp leading edge in the surface brightness 12.4±0.1 kpc north and west of the galaxy center in the direction of M87 characteristic of a merger cold front due to M60's motion through the Virgo ICM. We measured a temperature of 1.00±0.02 keV for abundance 0.5Z⊙ inside the edge and 1.37+0.35−0.19 keV for abundance 0.1Z⊙ in the Virgo ICM free stream region. We find that the observed jump in surface brightness yields a density ratio of 6.44+1.04−0.67 between gas inside the edge and in the cluster free stream region. If the edge is a cold front due solely to the infall of M60 in the direction of M87, we find a pressure ratio of 4.7+1.7−1.4 and Mach number 1.7±0.3. For 1.37 keV Virgo gas we find a total infall velocity for M60 of 1030±180 kms−1. We calculate the motion in the plane of the sky to be 1012+183−192 km−1 implying an inclination angle ξ=11±3 degrees. Surface brightness profiles show the presence of a faint diffuse gaseous tail. We identify filamentary, gaseous wing structures caused by the galaxy's motion through the ICM. The structure and dimensions of these wings are consistent with simulations of Kelvin-Helmholtz instabilities as expected if the gas stripping is close to inviscid

Higgs and Dark Matter Hints of an Oasis in the Desert

Recent LHC results suggest a standard model (SM)-like Higgs boson in the vicinity of 125 GeV with no clear indications yet of physics beyond the SM. At the same time, the SM is incomplete, since additional dynamics are required to accommodate cosmological dark matter (DM). In this paper we show that interactions between weak scale DM and the Higgs which are strong enough to yield a thermal relic abundance consistent with observation can easily destabilize the electroweak vacuum or drive the theory into a non-perturbative regime at a low scale. As a consequence, new physics--beyond the DM itself--must enter at a cutoff well below the Planck scale and in some cases as low as O(10 - 1000 TeV), a range relevant to indirect probes of flavor and CP violation. In addition, this cutoff is correlated with the DM mass and scattering cross-section in a parameter space which will be probed experimentally in the near term. Specifically, we consider the SM plus additional spin 0 or 1/2 states with singlet, triplet, or doublet electroweak quantum numbers and quartic or Yukawa couplings to the Higgs boson. We derive explicit expressions for the full two-loop RGEs and one-loop threshold corrections for these theories.Comment: 29 pages, 13 figure

The Active Nucleus of IC4970: A Nearby Example of Merger-Induced Cold-Gas Accretion

We present results from Chandra X-ray and Spitzer mid-infrared observations of the interacting galaxy pair NGC6872/IC4970 in the Pavo galaxy group and show that the smaller companion galaxy IC4970 hosts a highly obscured active galactic nucleus (AGN). The 0.5-10 keV X-ray luminosity of the nucleus is variable, increasing by a factor 2.9 to 1.7 x 10^{42} erg/s (bright state) on ~100 ks timescales. The X-ray spectrum of the is heavily absorbed (N_H = 3 x 10^{23} cm^{-2}) for power law models with Gamma = 1.5-2.0 and shows a clear 6.4 keV Fe Kalpha line with equivalent width of 144-195 eV. Limits on the diffuse emission in IC4970 from Chandra X-ray data suggest that the available power from Bondi accretion of hot interstellar gas may be an order of magnitude too small to power the AGN. Spitzer images show that 8 micron nonstellar emission is concentrated in the central 1 kpc of IC4970, consistent with high obscuration in this region. The mid-infrared colors of the nucleus are consistent with those expected for a highly obscured AGN. Taken together these data suggest that the nucleus of IC4970 is a Seyfert 2, triggered and fueled by cold material supplied to the central supermassive black hole as a result of the off-axis collision of IC4970 with the cold-gas rich spiral galaxy NGC6872.Comment: 10 pages, 9 figures, submitted to ApJ, MIR flux conversion error corrected in Table 4, MIR colors and paper text unchange

Planck Scale Boundary Conditions and the Higgs Mass

If the LHC does only find a Higgs boson in the low mass region and no other new physics, then one should reconsider scenarios where the Standard Model with three right-handed neutrinos is valid up to Planck scale. We assume in this spirit that the Standard Model couplings are remnants of quantum gravity which implies certain generic boundary conditions for the Higgs quartic coupling at Planck scale. This leads to Higgs mass predictions at the electroweak scale via renormalization group equations. We find that several physically well motivated conditions yield a range of Higgs masses from 127-142 GeV. We also argue that a random quartic Higgs coupling at the Planck scale favors M_H > 150 GeV, which is clearly excluded. We discuss also the prospects for differentiating different boundary conditions imposed for \lambda(M_{pl}) at the LHC. A striking example is M_H = 127\pm 5 GeV corresponding to \lambda(M_{pl})=0, which would imply that the quartic Higgs coupling at the electroweak scale is entirely radiatively generated.Comment: 12 pages, 5 figures; references added and other minor improvements, matches version published in JHE

Stripped elliptical galaxies as probes of ICM physics : III. Deep Chandra observation of NGC 4552 - Measuring the viscosity of the intracluster medium

We present results from a deep (200 ks) Chandra observation of the early-type galaxy NGC 4552 (M89) which is falling into the Virgo cluster. Previous shallower X-ray observations of this galaxy showed a remnant gas core, a tail to the South of the galaxy, and twin `horns' attached to the northern edge of the gas core [machacek05a]. In our deeper data, we detect a diffuse, low surface brightness extension to the previously known tail, and measure the temperature structure within the tail. We combine the deep Chandra data with archival XMM-Newton observations to put a strong upper limit on the diffuse emission of the tail out to a large distance (10×the radius of the remnant core) from the galaxy center. In our two previous papers [roediger15a,roediger15b], we presented the results of hydrodynamical simulations of ram pressure stripping specifically for M89 falling into the Virgo cluster and investigated the effect of ICM viscosity. In this paper, we compare our deep data with our specifically tailored simulations and conclude that the observed morphology of the stripped tail in NGC 4552 is most similar to the inviscid models. We conclude that, to the extent the transport processes can be simply modeled as a hydrodynamic viscosity, the ICM viscosity is negligible. More generally, any micro-scale description of the transport processes in the high-β plasma of the cluster ICM must be consistent with the efficient mixing observed in the stripped tail on macroscopic scales

Matching conditions and Higgs mass upper bounds revisited

Matching conditions relate couplings to particle masses. We discuss the importance of one-loop matching conditions in Higgs and top-quark sector as well as the choice of the matching scale. We argue for matching scales $\mu_{0,t} \simeq m_t$ and $\mu_{0,H} \simeq max[ m_t, M_H ]$. Using these results, the two-loop Higgs mass upper bounds are reanalyzed. Previous results for $\Lambda\approx$ few TeV are found to be too stringent. For $\Lambda=10^{19}$ GeV we find $M_H < 180 \pm 4\pm 5$ GeV, the first error indicating the theoretical uncertainty, the second error reflecting the experimental uncertainty due to $m_t=175\pm6$ GeV.Comment: 20 pages, 6 figures; uses epsf and rotate macro

Remarks on the Upper Bounds on the Higgs Boson Mass from Triviality

We study the effects of the one-loop matching conditions on Higgs boson and top quark masses on the triviality bounds on the Higgs boson mass using $\beta_{\lambda}$ with corrected two-loop coefficients. We obtain quite higher results than previous ones and observe that the triviality bounds are not nearly influenced by varying top quark mass over the range measured at CDF and D0. The effects of typo errors in $\beta_{\lambda}^{(2)}$ and the one-loop matching condition on the top quark mass are negligible. We estimate the size of effects on the triviality bounds from the one-loop matching condition on the Higgs boson mass.Comment: 9 pages, tar'ed gzip'ed uuencoded files, LaTex, 5 PostScript figures. To appear in Physical Review

Chandra Observations of Gas Stripping in the Elliptical Galaxy NGC 4552 in the Virgo Cluster

We use a 54.4 ks Chandra observation to study ram-pressure stripping in NGC4552 (M89), an elliptical galaxy in the Virgo Cluster. Chandra images in the 0.5-2 keV band show a sharp leading edge in the surface brightness 3.1 kpc north of the galaxy center, a cool (kT =0.51^{+0.09}_{-0.06} keV) tail with mean density n_e ~5.4 +/- 1.7 x 10^{-3} cm^{-3} extending ~10 kpc to the south of the galaxy, and two 3-4 kpc horns of emission extending southward away from the leading edge. These are all features characteristic of supersonic ram-pressure stripping of galaxy gas, due to NGC4552's motion through the surrounding Virgo ICM. Fitting the surface brightness profile and spectra across the leading edge, we find the galaxy gas inside the edge is cooler (kT = 0.43^{+0.03}_{-0.02} keV) and denser (n_e ~ 0.010 cm^{-3}) than the surrounding Virgo ICM (kT = 2.2^{+0.7}_{-0.4} keV and n_e = 3.0 +/- 0.3 x 10^{-4} cm^{-3}). The resulting pressure ratio between the free-streaming ICM and cluster gas at the stagnation point is ~7.6^{+3.4}_{-2.0} for galaxy gas metallicities of 0.5^{+0.5}_{-0.3} Zsolar, which suggests that NGC4552 is moving supersonically through the cluster with a velocity v ~ 1680^{+390}_{-220} km/s (Mach 2.2^{+0.5}_{-0.3}) at an angle xi ~ 35 +/- 7 degrees towards us with respect to the plane of the sky.Comment: 31 pages, 12 figures, ApJ, in press; paper split into 2 parts, Paper I(sec 1-3) here, added figs and discussion to conform to published version; Paper II (sec. 4) in astro-ph/060440