14 research outputs found
The First Hi-GAL Observations of the Outer Galaxy: A Look at Star Formation in the Third Galactic Quadrant in the Longitude Range 216.º5 ≾ ℓ ≾ 225.º5
We present the first Herschel PACS and SPIRE photometric observations in a portion of the outer Galaxy (216.º5≾ℓ≾ 225.º5 and –2°≾b≾0°) as a part of the Hi-GAL survey. The maps between 70 and 500 μm, the derived column density and temperature maps, and the compact source catalog are presented. NANTEN CO(1-0) line observations are used to derive cloud kinematics and distances so that we can estimate distance-dependent physical parameters of the compact sources (cores and clumps) having a reliable spectral energy distribution that we separate into 255 proto-stellar and 688 starless sources. Both typologies are found in association with all the distance components observed in the field, up to ~5.8 kpc, testifying to the presence of star formation beyond the Perseus arm at these longitudes. Selecting the starless gravitationally bound sources, we identify 590 pre-stellar candidates. Several sources of both proto- and pre-stellar nature are found to exceed the minimum requirement for being compatible with massive star formation based on the mass-radius relation. For the pre-stellar sources belonging to the Local arm (d ≾ 1.5 kpc) we study the mass function whose high-mass end shows a power law N(log M)∝M^(–1.0 ± 0.2). Finally, we use a luminosity versus mass diagram to infer the evolutionary status of the sources, finding that most of the proto-stellar sources are in the early accretion phase (with some cases compatible with a Class I stage), while for pre-stellar sources, in general, accretion has not yet started
The first Hi-GAL observations of the outer Galaxy: a look to star formation in the third Galactic quadrant in the longitude range 216.5 < l < 225.5
We present the first Herschel PACS and SPIRE photometric observations in a
portion of the outer Galaxy ( and ) as a part of the
Hi-GAL survey. The maps between 70 and 500 m, the derived column density
and temperature maps, and the compact source catalog are presented. NANTEN
CO(1-0) line observations are used to derive cloud kinematics and distances, so
that we can estimate distance-dependent physical parameters of the compact
sources (cores and clumps) having a reliable spectral energy distribution, that
we separate in 255 proto-stellar and 688 starless. Both typologies are found in
association with all the distance components observed in the field, up to kpc, testifying the presence of star formation beyond the Perseus arm at
these longitudes. Selecting the starless gravitationally bound sources we
identify 590 pre-stellar candidates. Several sources of both proto- and
pre-stellar nature are found to exceed the minimum requirement for being
compatible with massive star formation, based on the mass-radius relation. For
the pre-stellar sources belonging to the Local arm ( kpc) we
study the mass function, whose high-mass end shows a power-law . Finally, we use a luminosity vs mass diagram to
infer the evolutionary status of the sources, finding that most of the
proto-stellar are in the early accretion phase (with some cases compatible with
a Class I stage), while for pre-stellar sources, in general, accretion has not
started yet.Comment: Accepted by Ap
The data reduction pipeline for the Hi-GAL survey
We present the data reduction pipeline for the Hi-GAL survey. Hi-GAL is a key
project of the Herschel satellite which is mapping the inner part of the
Galactic plane (|l| <= 70\cdot and |b| <= 1\cdot), using 2 PACS and 3 SPIRE
frequency bands, from 70{\mu}m to 500{\mu}m. Our pipeline relies only partially
on the Herschel Interactive Standard Environment (HIPE) and features several
newly developed routines to perform data reduction, including accurate data
culling, noise estimation and minimum variance map-making, the latter performed
with the ROMAGAL algorithm, a deep modification of the ROMA code already tested
on cosmological surveys. We discuss in depth the properties of the Hi-GAL
Science Demonstration Phase (SDP) data.Comment: 12 pages, 15 figures, MNRAS submitte
Artifact Removal for GLS Map Makers by Means of Post-Processing
The quality of astrophysical images produced by means of the generalized least square (GLS) approach may be degraded by the presence of artificial structures, obviously not present in the sky. This problem affects, in different degrees, all images produced by the instruments onboard the European Space Agency's Herschel satellite. In this paper, we analyze these artifacts and introduce a method to remove them. The method is based on a post-processing of GLS image that estimates and removes the artifacts subtracting them from the original image. We find that the only drawback of this method is a slight increase of the background noise which, however, can be mitigated by detecting the artifacts and by performing the subtraction only where they are detected. The efficiency of the approach is demonstrated and quantified using simulated and real data
Artifact Removal for GLS Map Makers by Means of Post-Processing
The quality of astrophysical images produced by means of the generalized least square (GLS) approach may be degraded by the presence of artificial structures, obviously not present in the sky. This problem affects, in different degrees, all images produced by the instruments onboard the European Space Agency's Herschel satellite. In this paper, we analyze these artifacts and introduce a method to remove them. The method is based on a post-processing of GLS image that estimates and removes the artifacts subtracting them from the original image. We find that the only drawback of this method is a slight increase of the background noise which, however, can be mitigated by detecting the artifacts and by performing the subtraction only where they are detected. The efficiency of the approach is demonstrated and quantified using simulated and real data
The On Board Software of the Herschel HIFI instrument
The Heterodyne Instrument for the Far-Infrared
onboard the ESA Herschel satellite is a heterodyne spec-
trometer with unprecedented frequency range, resolution and
sensibility. It is composed of two spectrometers, a Local
Oscillator Unit, producing the mixing signals, a Focal Plane
Unit, perfoming mixing and amplification, and an Instrument
Control Unit, hosting a DSP where the On Board Software
(OBS) runs. The OBS coordinates the other units, manages
the interface with the spacecraft and monitors the instrument
status. A synthetic description of the OBS organization and
functioning is presented in this pape
Best Paper Award
The Heterodyne Instrument for the Far-Infrared onboard the ESA Herschel satellite is a heterodyne spec- trometer with unprecedented frequency range, resolution and sensibility. It is composed of two spectrometers, a Local Oscillator Unit, producing the mixing signals, a Focal Plane Unit, perfoming mixing and amplification, and an Instrument Control Unit, hosting a DSP where the On Board Software (OBS) runs. The OBS coordinates the other units, manages the interface with the spacecraft and monitors the instrument status. A synthetic description of the OBS organization and functioning is presented in this pape
The first hi-gal observations of the outer galaxy: A look at star formation in the third galactic quadrant in the longitude range 216.°5 ≲ ℓ ≲ 225.°5
We present the first Herschel PACS and SPIRE photometric observations in a portion of the outer Galaxy (216.°5 ≲ ℓ ≲ 225.°5 and -2° ≲ b ≲ 0°) as a part of the Hi-GAL survey. The maps between 70 and 500 μm, the derived column density and temperature maps, and the compact source catalog are presented. NANTEN CO(1-0) line observations are used to derive cloud kinematics and distances so that we can estimate distance-dependent physical parameters of the compact sources (cores and clumps) having a reliable spectral energy distribution that we separate into 255 proto-stellar and 688 starless sources. Both typologies are found in association with all the distance components observed in the field, up to 5.8 kpc, testifying to the presence of star formation beyond the Perseus arm at these longitudes. Selecting the starless gravitationally bound sources, we identify 590 pre-stellar candidates. Several sources of both proto- and pre-stellar nature are found to exceed the minimum requirement for being compatible with massive star formation based on the mass-radius relation. For the pre-stellar sources belonging to the Local arm (d ≲ 1.5 kpc) we study the mass function whose high-mass end shows a power law N(log M)M -1.0 ± 0.2. Finally, we use a luminosity versus mass diagram to infer the evolutionary status of the sources, finding that most of the proto-stellar sources are in the early accretion phase (with some cases compatible with a Class I stage), while for pre-stellar sources, in general, accretion has not yet started. © 2013. The American Astronomical Society. All rights reserved