P. L. Hammersley

Spectral Irradiance Calibration in the Infrared. X. A Self-Consistent Radiometric All-Sky Network of Absolutely Calibrated Stellar Spectra*

We start from our six absolutely calibrated continuous stellar spectra from 1.2 to 35 ?m for K0, K1.5, K3, K5, and M0 giants. These were constructed as far as possible from actual observed spectral fragments taken from the ground, the Kuiper Airborne Observatory, and the IRAS Low Resolution Spectrometer, and all have a common calibration pedigree. From these we spawn 422 calibrated spectral templates for stars with spectral types in the ranges G9.5?K3.5 III and K4.5?M0.5 III. We normalize each template by photometry for the individual stars using published and/or newly secured near- and mid-infrared photometry obtained through fully characterized, absolutely calibrated, combinations of filter passband, detector radiance response, and mean terrestrial atmospheric transmission. These templates continue our ongoing effort to provide an all-sky network of absolutely calibrated, spectrally continuous, stellar standards for general infrared usage, all with a common, traceable calibration heritage. The wavelength coverage is ideal for calibration of many existing and proposed ground-based, airborne, and satellite sensors, particularly low- to moderate-resolution spectrometers. We analyze the statistics of probable uncertainties, in the normalization of these templates to actual photometry, that quantify the confidence with which we can assert that these templates truly represent the individual stars. Each calibrated template provides an angular diameter for that star. These radiometric angular diameters compare very favorably with those directly observed across the range from 1.6 to 21 mas.

Old stellar Galactic disc in near-plane regions according to 2MASS: Scales, cut-off, flare and warp

We have pursued two dierent methods to analyze the old stellar population near the Galactic plane, using data from the 2MASS survey. The first method is based on the isolation of the red clump giant population in the color-magnitude diagrams and the inversion of its star counts to obtain directly the density distribution along the line of sight. The second method fits the parameters of a disc model to the star counts in 820 regions. Results from both independent methods are consistent with each other. The qualitative conclusions are that the disc is well fitted by an exponential distribution in both the galactocentric distance and height. There is not an abrupt cut-o in the stellar disc (at least within R 6 kpc) that: the scale- height in the solar circle is hz(R)= 3:6 10 2 R, the scale-length of the surface density is hR= 0:42 R and the scale-length of the space density in the plane (i.e. including the eect of the flare) is H= 0:25 R. The variation of the scale-height due to the flare follows roughly a law hz(R) hz(R )e xp R R (12 0:6R(kpc)) kpc (for R< 15 kpc; R= 7:9 kpc). The warp moves the mean position of the disc to a height zw= 1:2 10 3 R(kpc) 5:25 sin(+ 5) pc (for R< 13 kpc; R= 7:9 kpc).

Tracing the long bar with red-clump giants

Context. Over the last decade a series of results have lent support to t he hypothesis of the existence of a long thin bar in the Milky Way with a half-length of 4.5 kpc and a position angle of around 45 ◦ . This is apparently a very different structure from the triaxial bulge of the Galaxy. Aims. In this paper, we analyse the stellar distribution in the inn er 4 kpc of the Galaxy to see if there is clear evidence for two triaxial or barlike structures, or whether there is only one. Methods. By using the red-clump population as a tracer of the structure of the inner Galaxy we determine the apparent morphology of the inner Galaxy. Star counts from 2MASS are used to provide additional support for this analysis. Results. We show that there are two very different large-scale triaxial structures coexisting in the in ner Galaxy: a long thin stellar bar constrained to the Galactic plane (|b| < 2 ◦ ) with a position angle of 43. ◦ 0±1. ◦ 8, and a distinct triaxial bulge that extends to at least |b| ≤ 7.5 ◦ with a position angle of 12. ◦ 6±3. ◦ 2. The scale height of the bar source distribution is around 100 pc, whereas for the bulge

The Long Bar in the Milky Way: Corroboration of an Old Hypothesis

Recent Galactic Legacy Infrared Mid-Plane Survey Extraordinaire data have further confirmed the hypothesis of the existence of an in-plane long bar different from the bulge of the Milky Way with the same characteristics as emphasized some years ago by our team. In this paper we present two new analyses that corroborate recent and earlier claims concerning the existence in our Galaxy of a long, flat bar with approximate dimensions of 7.8 kpc ? 1.2 kpc ? 0.2 kpc and a position angle of approximately 43?: (1) star counts with 2MASS All-Sky Data Release and Midcourse Space Experiment data, which give an excess in the plane region along 0? < l < 30? compared with -30? < l < 0? that cannot be due to the bulge, spiral arms, a ring, or extinction; and (2) new data on the distance of the long bar using the red clump method, together with recent observations of our own that are compared with our model and that are in agreement with the long-bar scenario.

The thick disc component of the Galaxy from near infrared colour-magnitude diagrams

The vertical distribution of K giants stars is analyzed using 2MASS data and a semiempirical method of extracting stellar densities from the K/J − K colour-magnitude diagrams. The vertical density distribution of red clump giant stars can be described by a double exponential, with scaleheights of 268.81 ± 12.65 pc and 1061.9 ± 52.16 pc. These values are in agreement with the expected values for the thin and thick disc components of the Milky Way. For the thick disc, the radial scalelength is also obtained, with a value of hR = 3.04 ± 0.11 kpc.

Searching for the in-plane Galactic bar and ring in DENIS

New evidence for a long thin Galactic bar (in contradistinction to the bulge), as well as for the existence of the ring and the truncation of the inner disc, are sought in the DENIS survey. First, we examine DENIS and Two Micron Galactic Survey star counts for the characteristic signatures of an in-plane bar and ring. The star counts in the plane for

Inversion of stellar statistics equation for the Galactic bulge

30^\circ> l> -30^\circ

Radiometric Validation of the Midcourse Space Experiment’s (MSX) Point Source Catalogs and the MSX Properties of Normal Stars

are shown to be highly asymmetric with considerably more sources at positive than at negative longitudes. At

ISOPHOT { Photometric calibration of point sources

|b|\approx 1.5^\circ

A Major Star Formation Region in the Receding Tip of the Stellar Galactic Bar

, however, the counts are nearly symmetric. Therefore, the asymmetry is not due to the disc, which is shown to have an inner truncation, or to the bulge, so there has to be another major component in the inner Galaxy that is causing the asymmetries. This component provides up to 50% of the detected sources in the plane between the bulge and