arXiv subjects

M. Grossi

Publications and source records attributed to M. Grossi.

70 records · Page 4Linked to original sources

arXiv2006

GRBs, SGRs by UHE leptons showering, blazing and re-brightening by precessing Gamma Jets in-off axis

A list of questions regarding Gamma Ray Bursts (GRBs) and Soft Gamma Repeaters (SGRs) remain unanswered within the Fireball-cone and Magnetar explosive scenarios. A persistent, thin (less than micron-sr solid angle) precessing and spinning gamma jet, with a power output comparable to the progenitor supernova (SN) or XRay pulsar, may explain these issues. The precessing jets may have a few hours characteristic decay time, while their decreasing intensity follow a power law for thousands of years. The orientation of the spinning and precessing beam respect to the line of sight plays a key role : the farthest GRB events in widest cosmic volumes correspond generally to a very narrow and on-axis beam, while for the nearest ones sources are mostly observable off-axis. Consequentely the far ones are the hardest and the most bright and viceversa nearest one are mostly softer and longest ones as in Amati correlation. We expect that nearby off-axis GRBs would be accompanied by a chain of OT and radio bumps as in GRB030329-SN2003 and latest GRB060218-SN2006 events. Delayed blazing jets are observable in the local universe as X-Ray Flahes (XRFs) or short GRBs often as orphan afterglow event, and at closer distances as SGRs and anomalous X-ray Pulsars AXRPs. The gamma jet is originated by ultra-relativistic electron pairs showering via Synchrotron (or Inverse Compton) radiation. The electron pairs escape from the inner SN core thanks to a more penetrating couriers, the relativistic PeV muon pairs, themselves secondaries of inner UHE hadron jets. They are 'transparent' through the SN shells of matter and lights; they decay far away in to electron pairs (and later on) in gamma and neutrinos jets. Then GRBs (and SGRs) are not the most explosive event of the Universe, but just the most beamed ones.

astro-ph↗

arXiv2006

Crown Detectors to Observe Horizontal and Upward Air-Showers

Cerenkov Telescopes and Scintillators set on a Crown-like arrays facing the Horizons may reveal far Cosmic Rays Showers, nearer Anti-Neutrino-Electron + Electron --> W- shower in air and upgoing Tau Neutrino + N--> tau + X, --> Shower, Earth-Skimming tau air-showers. Even UHE SUSY Chi + e--> Selectron--> Chi + e at tens PeVs-EeV energy may blaze at Horizons, as anti-neutrino electron at Glashow peak - Burst shower. We show first estimate on down and up-going Horizontal Showers traces for present and future Magic-like Crown Arrays and their correlated Scintillator-like twin Crown Arrays. The one mono or stereo-Magic elements facing the Horizons are already comparable to present Amanda underground neutrino detector.

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arXiv2005

A Dark Galaxy in the Virgo Cluster Imaged at 21-cm

Dark Matter supposedly dominates the extragalactic, yet no totally dark structure of galactic proportions has ever been convincingly identified. Earlier (Minchin et al. 2005) we suggested that VIRGOHI 21, a 21-cm source we found in the Virgo Cluster at Jodrell Bank using single-dish observations (Davies et al. 2004), was probably such a dark galaxy because of its broad line-width (~ 200 km/s) unaccompanied by any visible gravitational source to account for it. Now we have managed to image VIRGOHI 21 in the neutral-hydrogen line, and indeed we find what appears to be a dark, edge-on, spinning disc with the mass and diameter of a typical spiral galaxy. Moreover the disc has unquestionably interacted with NGC 4254, a luminous spiral with an odd one-armed morphology, but lacking the massive interactor invariably responsible for such a feature. Published numerical models (Vollmer, Huchtmeier & van Driel 2005) of NGC 4254 call for a close interaction ~ 10^8 years ago with a perturber of 10^11 solar masses. This we take as completely independent evidence for the massive nature of VIRGOHI 21.

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arXiv2005

UHE Leptons and Neutrons feeding Precessing gamma Jet in GRBs - SGRs: A SGR 1806-20 link to EeV C.R.?

Soft Gamma Repeaters are widely believed to occur as isotropic Magnetar explosion. We suggest on the contrary that they may be described by thin collimated spinning and precessing Gamma Jets flashing and blazing along the line of sight. The Jet (for SGRs) maybe powered by an accretion disk in binary system and it reproduces huge outflow and oscillating blazing mode as the observed ones in Giant Flare SGR 1806-20. The precessing and spinning blazing nature reflects at smaller intensity the same behavior observed in brief GRBs Jetted Supernova, as well as re-brightening and bumps in afterglows. The SGR gamma beam maybe powered by Inverse Compton Scattering or by Synchrotron Radiation of electron pair beam respectively at GeVs or PeVs energies. In the latter case tens PeVs leptons (muons and later decaying PeVs electrons) might be originated while EeV nucleons Jets (protons-neutrons) are in photo-pion equilibrium with infrared photons surrounding the source. The neutron Jet might survive and remain collimated. It maybe already detected as an EeV cosmic ray anisotropy in present AGASA map pointing toward known (North Hemisphere) SGRs : SGR 1900 +14 and SGR 1806-20. If the SGR-EeV connection is correct a parasite traces of PeVs neutrino as well PeV-TeVs gamma rays might be found in present or future data records, among the others C.R. array detectors, inside the Amanda and Milagro volumes.

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arXiv2005

GRBs and SGRs by high energy leptons showering in blazing gamma jets: are SGRs sources of EeV CRs?

The apparently huge energy budget of the gamma ray burst GRB 990123 led to the final collapse of the isotropic fireball model, forcing even the most skeptical to consider a beamed Jet emission correlated to a supernova (SN) explosion. Similarly the surprising giant flare from the soft gamma repeater SGR 1806-20 that occurred on 2004 December 27, may induce the crisis of the magnetar model. If the apparently huge energy associated to this flare has been radiated isotropically, the magnetar should have consumed at once most of (if not all) the energy stored in the magnetic field. On the contrary we think that a thin collimated precessing jet, blazing on-axis, may be the source of such apparently huge bursts with a moderate output power. We discuss the possible role of the synchrotron emission and electromagnetic showering of PeV electron pairs from muon bundles. A jet made of muons may play a key role in avoiding the opacity of the SN-GRB radiation field. We propose a similar mechanism to explain the emission of SGRs. In this case we also examine the possibility of a primary hadronic jet that would produce ultra relativistic e+ e- (1 - 10 PeV) from pion- muon or neutron decay. Such electron pairs would emit a few hundreds keV radiation from their interaction with the galactic magnetic field, as it is observed in the intense gamma ray flare from SGR 1806-20. A thin precessing jet from a pulsar may naturally explain the negligible variation of the spin frequency. A correlation between SGR 1806-20, SGR 1900 +14, Cygnus and the AGASA excess of EeV cosmic rays (CRs) has been found; we suggest that a robust EeV signal may be detected by AUGER or Milagro in the near future.

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arXiv2005

Rates of Horizontal Tau Air-Showers observable by satellites

Up-going and Horizontal Tau Air-Showers, UpTaus and HorTaus, may trace Ultra High Energy Neutrino Tau Earth Skimming at the edge of the horizon. We show that such events even for minimal GZK neutrino fluxes could be detected by space telescopes such as the EUSO project. These Horizontal Tau Showers will track very long fan-like, multi-finger showers whose signature would be revealed by EUSO, OWL experiments. Moreover the additional imprint of their young secondaries muon, electron pairs and gamma bundles flashes might allow to disentangle their nature from the older UHECR secondaries in horizontal showers. Indeed at large zenith angles, the muon, electron pairs and gamma number for far and old Ultra High Energy Cosmic Rays, becomes comparable. On the contrary up-ward muon bundles from UpTaus and HorTaus (as well as by anti-neutrino electron + electron resonance at Glashow peak) may arise within a young shower with a gamma-muon ratio as large as 10^2. Such a very characteristic imprint maybe observed by Crown detector arrays on Mountain, planes or balloons in space, as well as by gamma satellites in Space. We estimate the UpTaus and HorTaus rate from the Earth and the consequent event rate of +/-mu bundles, whose flux at 92^o -97^o may exceed the up-going muon flux induced by the atmospheric neutrino, by one or two order of magnitude.

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arXiv2004

The cosmological significance of Low Surface Brightness galaxies found in a deep blind neutral-hydrogen survey

We have placed limits on the cosmological significance of gas-rich low surface-brightness (LSB) galaxies as a proportion of the total population of gas-rich galaxies by carrying out a very deep survey (HIDEEP) for neutral hydrogen (HI) with the Parkes multibeam system. Such a survey avoids the surface-brightness selection effects that limit the usefulness of optical surveys for finding LSB galaxies. To complement the HIDEEP survey we have digitally stacked eight 1-hour R-band Tech Pan films from the UK Schmidt Telescope covering 36 square degrees of the survey area to reach a very deep isophotal limit of 26.5 R mag/sq. arcsec. At this level, we find that all of the 129 HI sources within this area have optical counterparts and that 107 of them can be identified with individual galaxies. We have used the properties of the galaxies identified as the optical counterparts of the HI sources to estimate the significance of LSB galaxies (defined to be those at least 1.5 magnitudes dimmer in effective surface-brightness than the peak in the observed distribution seen in optical surveys). We calculate the contribution of LSB galaxies to the total number, neutral hydrogen density, luminosity density, baryonic mass density, dynamical mass density and cross-sectional area of gas-rich galaxies. We do not find any `Crouching Giant' LSB galaxies such as Malin 1, nor do we find a population of extremely low surface-brightness galaxies not previously found by optical surveys. Such objects must either be rare, gas-poor or outside the survey detection limits.

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arXiv2004

Muon and Gamma Bundles tracing Up-going Tau Neutrino Astronomy

Up-going and Horizontal Tau Air-Showers, UpTaus and HorTaus, may trace Ultra High Energy Neutrino Tau Earth Skimming at the edge of the horizons. Their secondaries muon, electron pairs, and gamma bundles flashes might trace their nature over UHECR secondaries in horizontal showers. Indeed the atmosphere act as a perfect amplifier as well as a filter for showers: down-ward and horizontal muon bundles may still be originated by far Ultra High Energy Cosmic Rays skimming the terrestrial atmosphere but their rich gamma component will be exponentially suppressed. At large zenith angles after crossing a large slant depth X > 3 10^3 g cm^-2 the number of muons and secondary gamma (produced by the electron pair from muon decay in flight) is comparable. On the other hand, up-ward muon bundles from UpTaus and HorTaus may arise within a young shower with a larger gamma-muon ratio 10^2, leaving a characteristic imprint. We estimate the UpTaus and HorTaus rate from the Earth and we evaluate the consequent event rate of muons, electrons pairs andgamma bundles. We show that such events even for minimal GZK neutrino fluxes could be detected by scintillator arrays placed on mountains at 1-5km and pointing to the horizon. The required arrayareas are within tens-hundreds of square meters. The ideal structure is an array of crown-like twin detectors facing the horizons. We argue that such detectors will be able to detect both muonic bundles at a minimal average flux of 10^-11 cm-2 s^-1 sr^-1 and electromagnetic particles gamma and electron pairs 3 10^-9 cm^-2 s^-1 sr^-1, a few times each year for GZK neutrino fluxes.

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arXiv2003

Properties of three gas-rich dwarfs in the Centaurus A group

We present HST/WFPC2 observations (F555W, F814W) and ATCA high resolution HI maps of three gas-rich dwarf galaxies in the Centaurus A group discovered in two blind 21-cm surveys (HIPASS, HIDEEP). We compare their individual properties and discuss their star formation history. Although we can not constrain the age of the oldest population from the diagrams very well, the presence of an extended population of red giant stars suggests that these systems were not formed recently. The presence of asymptotic giant branch (AGB) stars in two out of three dwarfs, sets a lower limit on the age of about 6 Gyr.

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arXiv2003

HIDEEP - An extragalactic blind survey for very low column-density neutral hydrogen

We have carried out an extremely long integration-time (9000 s/beam) 21-cm blind survey of 60 square degrees in Centaurus using the Parkes multibeam system. We find that the noise continues to fall as sqrt(t) throughout, enabling us to reach an HI column-density limit of 4.2 x 10^18 cm^-2 for galaxies with a velocity width of 200 km/s in the central 32 square degree region, making this the deepest survey to date in terms of column density sensitivity. The HI data are complemented by very deep optical observations from digital stacking of multi-exposure UK Schmidt Telescope R-band films, which reach an isophotal level of 26.5 R mag arcsec^-2 (~27.5 B mag arcsec^-2). 173 HI sources have been found, 96 of which have been uniquely identified with optical counterparts in the overlap area. There is not a single source without an optical counterpart. Although we have not measured the column-densities directly, we have inferred them from the optical sizes of their counterparts. All appear to have a column-density of N_HI = 10^(20.65 +/- 0.38). This is at least an order of magnitude above our sensitivity limit, with a scatter only marginally larger than the errors on N_HI. This needs explaining. If confirmed it means that HI surveys will only find low surface brightness (LSB) galaxies with high M_HI/L_B. Gas-rich LSB galaxies with lower HI mass to light ratios do not exist. The paucity of low column-density galaxies also implies that no significant population will be missed by the all-sky HI surveys being carried out at Parkes and Jodrell Bank.

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arXiv2003

First Results from the HI Jodrell All Sky Survey: Inclination-Dependent Selection Effects in a 21-cm Blind Survey

Details are presented of the HI Jodrell All Sky Survey (HIJASS). HIJASS is a blind neutral hydrogen (HI) survey of the northern sky, being conducted using the multibeam receiver on the Lovell Telescope at Jodrell Bank. HIJASS covers the velocity range -3500 km/s to 10000 km/s with a velocity resolution of 18.1 km/s and a spatial positional accuracy of ~2.5 arcmin. Thus far about 1115 sq deg have been surveyed. We describe the methods of detecting galaxies within the HIJASS data and of measuring their HI parameters. The properties of the resulting HI-selected sample of galaxies are described. Of the 222 sources so far confirmed, 170 (77 per cent) are clearly associated with a previously catalogued galaxy. A further 23 sources (10 percent) lie close (within 6 arcmin) to a previously catalogued galaxy for which no previous redshift exists. A further 29 sources (13 per cent) do not appear to be associated with any previously catalogued galaxy. The distributions of peak flux, integrated flux, HI mass and cz are discussed. We show, using the HIJASS data, that HI self-absorption is a significant, but often overlooked, effect in galaxies with large inclination angles to the line of sight. Properly accounting for it could increase the derived HI mass density of the local Universe by at least 25 per cent. The effect this will have on the shape of the HI Mass Function will depend on how self-absorption affects galaxies of different morphological types and HI masses. We also show that galaxies with small inclinations to the line of sight may also be excluded from HI-selected samples, since many such galaxies will have observed linewidths which are too narrow for them to be distinguished from narrow-band radio frequency interference.

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arXiv2002

Ultra High Energy Cosmic Ray and UHE Neutrino-Z Showering in Dark Halos

The Ultra High Energy Cosmic Ray (UHECR), by UHE neutrino-relic neutrino--Z showering in Hot Dark Halos (HDM), shows an energy spectra, an anisotropy following the relic neutrino masses and clustering in dark halo. The lighter are the relic neutrinos masses, the higher their corresponding Z resonance energy peaks. A twin light neutrino mass splitting may reflect into a twin Z resonance and a complex UHECR spectra modulation as a twin bump at at highest GZK energy cut-off. Each possible neutrino mass associates a characteristic dark halo size (galactic, local, super cluster) and its anisotropy due to our peculiar position within that dark matter distribution. The expected Z or WW,ZZ showering into proton-anti proton and neutron-anti neutron might correspond to peculiar clustering in observed UHECR at 10^{19}, 2 10^{19}, 4 10^{19} eV. A neutrino light HDM halo around a Mpc will allow to the UHECR neutron--anti-neutron secondary component at E_n> 10^{20} eV (due to Z decay) to arise playing a role comparable with the charged p-bar{p} ones. Their un-deflected n-bar{n} flight is shorter leading to a prompt and hard UHECR trace pointing toward the original UHECR source direction. The direct proton-antiproton pairs are split and spread by random magnetic fields into a more diluted and smeared and lower energy UHECR signal around the original source direction. Additional prompt TeVs signals by synchrotron radiation of electro-magnetic Z showering must also occur solving the Infrared-TeV cut-off. The observed hard doublet and triplets spectra, their time and space clustering already favour the rising key role of UHECR n-bar n secondaries originated by neutrino-Z tail shower.

hep-ph↗

arXiv2001

A blind HI survey of the M81 group

Results are presented of the first blind HI survey of the M81 group of galaxies. The data were taken as part of the HI Jodrell All Sky Survey (HIJASS). The survey reveals several new aspects to the complex morphology of the HI distribution in the group. All four of the known dwarf irregular (dIrr) galaxies close to M81 can be unambiguously seen in the HIJASS data. Each forms part of the complex tidal structure in the area. We suggest that at least three of these galaxies may have formed recently from the tidal debris in which they are embedded. The structure connecting M81 to NGC2976 is revealed as a single tidal bridge of mass approx. 2.1 x 10^8 Msol and projected spatial extent approx. 80 kpc. Two `spurs' of HI projecting from the M81 complex to lower declinations are traced over a considerably larger spatial and velocity extent than by previous surveys. The dwarf elliptical (dE) galaxies BK5N and Kar 64 lie at the spatial extremity of one of these features and appear to be associated with it. We suggest that these may be the remnants of dIrrs which has been stripped of gas and transmuted into dEs by close gravitational encounters with NGC3077. The nucleated dE galaxy Kar 61 is unambiguously detected in HI for the first time and has an HI mass of approx.10^8 Msol, further confirming it as a dE/dIrr transitional object. HIJASS has revealed one new possible group member, HIJASS J1021+6842. This object contains approx. 2 x 10^7 Msol of HI and lies approx.105arcmin from IC2574. It has no optical counterpart on the Digital Sky Survey.

astro-ph↗

arXiv2001

Ultra High Energy Neutrino-Relic Neutrino Interactions In Dark Halos to Solve Infrared-Tev And GZK Cut-Off

Ultra High Energy Neutrino scattering on Relic Light Neutrinos in Dark Galactic or Local Group lead to Z and WW,ZZ showering: the nucleon component of the shower may overcome the GZK cut-off while the electro-magnetic tail at TeVs up to EeVs energy may solve the Infrared-TeV cut-off in a natural way. Different Gamma TeV puzzles may find a solution within this scenario: new predictions on UHECR spectra in future data are derived.

astro-ph↗

arXiv2001

Shadows of Relic Neutrino Masses and Spectra on Highest Energy GZK Cosmic Rays

The Ultra High Energy (UHE) neutrino scattering onto relic cosmic neutrinos in galactic and local halos offers an unique way to overcome GZK cut-off. The UHE nu secondary of UHE photo-pion decays may escape the GZK cut-off and travel on cosmic distances hitting local light relic neutrinos clustered in dark halos. The Z resonant production and the competitive W^+W^-, ZZ pair production define a characteristic imprint on hadronic consequent UHECR spectra. This imprint keeps memory both of the primary UHE nu spectra as well as of the possible relic neutrino masses values, energy spectra and relic densities. Such an hadronic showering imprint should reflect into spectra morphology of cosmic rays near and above GZK 10^{19}-10^{21}eV cut-off energies. A possible neutrino degenerate masses at eVs or a more complex and significant neutrino mass split below or near Super-Kamiokande \triangle m_{ν_{SK}}= 0.1 eV masses might be reflected after each corresponding Z peak showering, into new twin unexpected UHECR flux modulation behind GZK energies: E_{p} sim 3(frac{triangle m_{ν_{SK}}}/m_ν10^{21}),eV. Other shadowsof lightest, nearly massless, neutrinos m_{nu_{2K} simeq 0.001eV simeq kT_ν, their lowest relic temperatures, energies and densities might be also reflected at even higher energies edges near Grand Unification: E_{p} \sim 2.2(m_{ν_{2K}/E_ν})10^{23}, eV .

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arXiv1999

On the Heavy Relic Neutrino - Galactic Gamma Halo Connection

A halo model with heavy relic neutrinos N belonging to a fourth generation and their annihilations in galactic halo may explain the recent evidence of diffused gamma (GeV) radiation around galactic plane. We considered a neutrino mass in the narrow range ($M_Z/2 < m_N < M_Z$) and two main processes as source of gamma rays. A first one is ICS of ultrarelativistic electron pair on IR and optical galactic photons and a second due to prompt gammas by $π^0$ decay, leading to a gamma flux ($10^{-7} - 10^{-6} /(cm^2 s sr)$) comparable to EGRET detection. Our predictions are also compatible with the narrow window of neutrino mass $45 GeV < m_N < 60 GeV$, required to explain the recent underground DAMA positive signals.

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