Esempio n. 1
0
def add_pulsar_parameters(
    table,
    B_mean=12.05,
    B_stdv=0.55,
    P_mean=0.3,
    P_stdv=0.15,
    random_state="random-seed",
):
    """Add pulsar parameters to the table.

    For the initial normal distribution of period and logB can exist the following
    Parameters: B_mean=12.05[log Gauss], B_stdv=0.55, P_mean=0.3[s], P_stdv=0.15

    Parameters
    ----------
    random_state : {int, 'random-seed', 'global-rng', `~numpy.random.RandomState`}
        Defines random number generator initialisation.
        Passed to `~gammapy.utils.random.get_random_state`.
    """
    random_state = get_random_state(random_state)
    # Read relevant columns
    age = table["age"].quantity

    # Draw the initial values for the period and magnetic field
    def p_dist(x):
        return np.exp(-0.5 * ((x - P_mean) / P_stdv) ** 2)

    p0_birth = draw(0, 2, len(table), p_dist, random_state=random_state)
    p0_birth = Quantity(p0_birth, "s")

    log10_b_psr = random_state.normal(B_mean, B_stdv, len(table))
    b_psr = Quantity(10 ** log10_b_psr, "G")

    # Compute pulsar parameters
    psr = Pulsar(p0_birth, b_psr)
    p0 = psr.period(age)
    p1 = psr.period_dot(age)
    p1_birth = psr.P_dot_0
    tau = psr.tau(age)
    tau_0 = psr.tau_0
    l_psr = psr.luminosity_spindown(age)
    l0_psr = psr.L_0

    # Add columns to table
    table["P0"] = Column(p0, unit="s", description="Pulsar period")
    table["P1"] = Column(p1, unit="", description="Pulsar period derivative")
    table["P0_birth"] = Column(p0_birth, unit="s", description="Pulsar birth period")
    table["P1_birth"] = Column(
        p1_birth, unit="", description="Pulsar birth period derivative"
    )
    table["CharAge"] = Column(tau, unit="yr", description="Pulsar characteristic age")
    table["Tau0"] = Column(tau_0, unit="yr")
    table["L_PSR"] = Column(l_psr, unit="erg s-1")
    table["L0_PSR"] = Column(l0_psr, unit="erg s-1")
    table["B_PSR"] = Column(
        b_psr, unit="Gauss", description="Pulsar magnetic field at the poles"
    )
    return table
Esempio n. 2
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def make_base_catalog_galactic(
    n_sources,
    rad_dis="YK04",
    vel_dis="H05",
    max_age="1e6 yr",
    spiralarms=True,
    n_ISM="1 cm-3",
    random_state="random-seed",
):
    """Make a catalog of Galactic sources, with basic source parameters.

    Choose a radial distribution, a velocity distribution, the number
    of pulsars n_pulsars, the maximal age max_age[years] and the fraction
    of the individual morphtypes. There's an option spiralarms. If set on
    True a spiralarm modeling after Faucher&Kaspi is included.

    max_age and n_sources effectively correspond to s SN rate:
    SN_rate = n_sources / max_age

    Parameters
    ----------
    n_sources : int
        Number of sources to simulate
    rad_dis : callable
        Radial surface density distribution of sources
    vel_dis : callable
        Proper motion velocity distribution of sources
    max_age : `~astropy.units.Quantity`
        Maximal age of the source
    spiralarms : bool
        Include a spiralarm model in the catalog?
    n_ISM : `~astropy.units.Quantity`
        Density of the interstellar medium
    random_state : {int, 'random-seed', 'global-rng', `~numpy.random.RandomState`}
        Defines random number generator initialisation.
        Passed to `~gammapy.utils.random.get_random_state`.

    Returns
    -------
    table : `~astropy.table.Table`
        Catalog of simulated source positions and proper velocities
    """
    max_age = Quantity(max_age).to_value("yr")
    n_ISM = Quantity(n_ISM).to("cm-3")
    random_state = get_random_state(random_state)

    if isinstance(rad_dis, str):
        rad_dis = radial_distributions[rad_dis]

    if isinstance(vel_dis, str):
        vel_dis = velocity_distributions[vel_dis]

    # Draw random values for the age
    age = random_state.uniform(0, max_age, n_sources)
    age = Quantity(age, "yr")

    # Draw spatial distribution
    r = draw(
        RMIN.to_value("kpc"),
        RMAX.to_value("kpc"),
        n_sources,
        pdf(rad_dis()),
        random_state=random_state,
    )
    r = Quantity(r, "kpc")

    if spiralarms:
        r, theta, spiralarm = FaucherSpiral()(r, random_state=random_state)
    else:
        theta = Quantity(random_state.uniform(0, 2 * np.pi, n_sources), "rad")
        spiralarm = None

    x, y = astrometry.cartesian(r, theta)

    z = draw(
        ZMIN.to_value("kpc"),
        ZMAX.to_value("kpc"),
        n_sources,
        Exponential(),
        random_state=random_state,
    )
    z = Quantity(z, "kpc")

    # Draw values from velocity distribution
    v = draw(
        VMIN.to_value("km/s"),
        VMAX.to_value("km/s"),
        n_sources,
        vel_dis(),
        random_state=random_state,
    )
    v = Quantity(v, "km/s")

    # Draw random direction of initial velocity
    theta = Quantity(random_state.uniform(0, np.pi, x.size), "rad")
    phi = Quantity(random_state.uniform(0, 2 * np.pi, x.size), "rad")

    # Compute new position
    dx, dy, dz, vx, vy, vz = astrometry.motion_since_birth(v, age, theta, phi)

    # Add displacement to birth position
    x_moved = x + dx
    y_moved = y + dy
    z_moved = z + dz

    table = Table()
    table["age"] = Column(age, unit="yr", description="Age of the source")
    table["n_ISM"] = Column(n_ISM, description="Interstellar medium density")
    if spiralarms:
        table["spiralarm"] = Column(spiralarm, description="Which spiralarm?")

    table["x_birth"] = Column(x, description="Galactocentric x coordinate at birth")
    table["y_birth"] = Column(y, description="Galactocentric y coordinate at birth")
    table["z_birth"] = Column(z, description="Galactocentric z coordinate at birth")

    table["x"] = Column(x_moved.to("kpc"), description="Galactocentric x coordinate")
    table["y"] = Column(y_moved.to("kpc"), description="Galactocentric y coordinate")
    table["z"] = Column(z_moved.to("kpc"), description="Galactocentric z coordinate")

    table["vx"] = Column(vx, description="Galactocentric velocity in x direction")
    table["vy"] = Column(vy, description="Galactocentric velocity in y direction")
    table["vz"] = Column(vz, description="Galactocentric velocity in z direction")
    table["v_abs"] = Column(v, description="Galactocentric velocity (absolute)")

    return table