Submillimeter imaging of the Galactic Center starburst Sgr B2. Warm molecular, atomic, and ionized gas far from massive star-forming cores

Abstract

We present 168 arcmin^2 spectral images of the Sgr B2 complex taken with Herschel/SPIRE-FTS. We detect ubiquitous emission from CO (up to J=12-11), H2O, [CI]492, 809 GHz, and [NII] 205 um lines. We also present maps of the SiO, N2H+, HCN, and HCO+ emission obtained with the IRAM30m telescope. The cloud environment dominates the emitted FIR (80%), H2O 752 GHz (60 %) mid-J CO (91%), and [CI] (93 %) luminosity. The region shows very extended [NII] emission (spatially correlated with the 24 and 70 um dust emission). The observed FIR luminosities imply G_0~10^3. The extended [CI] emission arises from a pervasive component of neutral gas with n_H~10^3 cm-3. The high ionization rates, produced by enhanced cosmic-ray (CR) fluxes, drive the gas heating to Tk~40-60 K. The mid-J CO emission arises from a similarly extended but more pressurized gas component (P_th~10^7 K cm-3). Specific regions of enhanced SiO emission and high CO-to-FIR intensity ratios (>10^-3) show mid-J CO emission compatible with shock models. A major difference compared to more quiescent star-forming clouds in the disk of our Galaxy is the extended nature of the SiO and N2H+ emission in Sgr B2. This can be explained by the presence of cloud-scale shocks, induced by cloud-cloud collisions and stellar feedback, and the much higher CR ionization rate (>10^-15 s-1) leading to overabundant H3+ and N2H+. Hence, Sgr B2 hosts a more extreme environment than star-forming regions in the disk of the Galaxy. As a usual template for extragalactic comparisons, Sgr B2 shows more similarities to ultra luminous infrared galaxies such as Arp 220, including a "deficit" in the [CI]/FIR and [NII]/FIR intensity ratios, than to pure starburst galaxies such as M82. However, it is the extended cloud environment, rather than the cores, that serves as a useful template when telescopes do not resolve such extended regions in galaxies.

arXiv commentAccepted for publication in A&A, 28 pages, 21 figures (abridged abstract)

References in corpus (101)

• Herschel Space Observatory - An ESA facility for far-infrared and submillimetre astronomy
• The Herschel-SPIRE instrument and its in-flight performance
• A computer program for fast non-LTE analysis of interstellar line spectra
• Infrared Emission from Interstellar Dust. II. The Diffuse Interstellar Medium
• Fermi Large Area Telescope Second Source Catalog
• Cold Dark Clouds: The Initial Conditions for Star Formation
• A geometric distance measurement to the Galactic Center black hole with 0.3% uncertainty
• MAMBO Mapping of Spitzer c2d Small Clouds and Cores
• Dense Cores in Dark Clouds. XIV. N2H+(1-0) maps of dense cloud cores
• Hi-GAL: the Herschel infrared Galactic Plane Survey
• A model for atomic and molecular interstellar gas: The Meudon PDR code
• Acceleration of petaelectronvolt protons in the Galactic Centre
• Rotational quenching of CO due to H${}_2$ collisions
• Far Infrared Spectroscopy of Normal Galaxies: Physical Conditions in the Interstellar Medium
• Investigating the Cosmic-Ray Ionization Rate in the Galactic Diffuse Interstellar Medium through Observations of H3+
• A 100-parsec elliptical and twisted ring of cold and dense molecular clouds revealed by Herschel around the Galactic Center
• Filamentary Accretion Flows in the Embedded Serpens South Protocluster
• Black hole accretion and star formation as drivers of gas excitation and chemistry in Mrk231
• Herschel PACS Spectroscopic Diagnostics of Local ULIRGs: Conditions and Kinematics in Mrk 231
• Observations of Arp 220 using Herschel-SPIRE: An Unprecedented View of the Molecular Gas in an Extreme Star Formation Environment
• Herschel Survey of Galactic OH+, H2O+, and H3O+: Probing the Molecular Hydrogen Fraction and Cosmic-Ray Ionization Rate
• The PdBI Arcsecond Whirlpool Survey (PAWS). I. A Cloud-Scale/Multi-Wavelength View of the Interstellar Medium in a Grand-Design Spiral Galaxy
• An ALMA study of the Orion Integral Filament: I. Evidence for narrow fibers in a massive cloud
• Molecular gas kinematics within the central 250 pc of the Milky Way
• A 2 mm spectral line survey of the starburst galaxy NGC 253
• Star Formation in the Central 400 pc of the Milky Way: Evidence for a Population of Massive YSOs
• Chemistry in Infrared Dark Cloud Clumps: a Molecular Line Survey at 3 mm
• The anatomy of the Orion B Giant Molecular Cloud: A local template for studies of nearby galaxies
• Far-Infrared Line Deficits in Galaxies with Extreme Lfir/MH2 Ratios
• A Chandra Study of Sgr A East: A Supernova Remnant Regulating The Activity Of Our Galactic Center?
• Spectral imaging of the Central Molecular Zone in multiple 3-mm molecular lines
• The Herschel Comprehensive (U)LIRG Emission Survey (HerCULES): CO Ladders, fine structure lines, and neutral gas cooling
• Dynamical Expansion of Ionization and Dissociation Front around a Massive Star. II. On the Generality of Triggered Star Formation
• Hard X-ray view of the past activity of Sgr A* in a natural Compton mirror
• The physical and chemical structure of Sagittarius B2, I. Three-dimensional thermal dust and free-free continuum modeling on 100 au to 45 pc scales
• Interstellar Hydrides
• Interacting Cosmic Rays with Molecular Clouds: A Bremsstrahlung Origin of Diffuse High Energy Emission from the Inner 2deg by 1deg of the Galactic Center
• Parsec-scale SiO Emission in an Infrared Dark Cloud
• Evidence for CO shock excitation in NGC 6240 from Herschel SPIRE spectroscopy
• Compression and ablation of the photo-irradiated cloud the Orion Bar
• Fading hard X-ray emission from the Galactic Centre molecular cloud Sgr B2
• Disruption of the Orion Molecular Core 1 by the stellar wind of the massive star ${\theta }^1$ Ori C
• Cloud-cloud collisions and triggered star formation
• Cosmic-ray induced destruction of CO in star-forming galaxies
• Velocity-resolved [CII] emission and [CII]/FIR Mapping along Orion with Herschel
• Impact of low-energy cosmic rays on star formation
• The far-IR spectrum of Sagittarius B2 region: Extended molecular absorption, photodissociation and photoionization
• Gravitational collapse of the OMC-1 region
• Dust-Bounded ULIRGs? Model Predictions for Infrared Spectroscopic Surveys
• SHINING, A Survey of Far Infrared Lines in Nearby Galaxies. II: Line-Deficit Models, AGN impact, [CII]-SFR Scaling Relations, and Mass-Metallicity Relation in (U)LIRGS
• Herschel observations of EXtraordinary Sources: Analysis of the full Herschel/HIFI molecular line survey of Sagittarius B2(N)
• The far-infrared spectrum of Arp 220
• Distributed star formation throughout the Galactic Center cloud Sgr B2
• Structure of photodissociation fronts in star-forming regions revealed by observations of high-J CO emission lines with Herschel
• Lambda = 3 mm line survey of nearby active galaxies
• ASCA Observations of the Sgr B2 Cloud: An X-Ray Reflection Nebula
• On the Origin of the Iron K Line in the Spectrum of the Galactic X-ray Background
• HNCO enhancement by shocks in the L1157 molecular outflow
• The complete far-infrared and submillimeter spectrum of the Class 0 protostar Serpens SMM1 obtained with Herschel. Characterizing UV-irradiated shocks heating and chemistry
• Physical conditions in the central molecular zone inferred by H3+
• Expanding bubbles in Orion A: [CII] observations of M42, M43, and NGC 1977
• Evolution of dust in the Orion Bar with Herschel: I. Radiative transfer modelling
• A Survey of the Molecular ISM Properties of Nearby Galaxies using the Herschel FTS
• High-J CO SLEDs in nearby infrared bright galaxies observed by Herschel-PACS
• Calibration of the Herschel SPIRE Fourier Transform Spectrometer
• Herschel observations of the Sgr B2 cores: Hydrides, warm CO, and cold dust
• Far-Infrared Spectroscopy of the Galactic Center. Hot Molecular Gas: Shocks versus Radiation near SgrA*
• Hard X-ray Morphological and Spectral Studies of The Galactic Center Molecular Cloud Sgr B2: Constraining Past Sgr A* Flaring Activity
• The Orion HII Region and the Orion Bar in the Mid-Infrared
• Photodissociation chemistry footprints in the Starburst galaxy NGC 253
• Herschel Far-Infrared Spectral-mapping of Orion BN/KL Outflows: Spatial distribution of excited CO, H2O, OH, O and C+ in shocked gas
• Water Vapor around Sgr B2
• Constraining physical conditions for the PDR of Trumpler 14 in the Carina Nebula
• Cloud-cloud Collision in the Galactic Center 50 km s${}^{-1}$ Molecular Cloud
• A high cluster formation efficiency in the Sagittarius B2 complex
• Absorption Line Survey of H3+ toward the Galactic Center Sources III. Extent of the Warm and Diffuse Clouds
• The physical and chemical structure of Sagittarius B2 -- V. Non-thermal emission in the envelope of Sgr B2
• An updated stellar census of the Quintuplet cluster
• Herschel-SPIRE-Fourier Transform Spectroscopy of the nearby spiral galaxy IC342
• Herschel SPIRE-FTS Observations of Excited CO and [CI] in the Antennae (NGC 4038/39): Warm and Cold Molecular Gas
• Non-thermal emission from cosmic rays accelerated in HII regions
• An X-ray survey of the central molecular zone: variability of the Fe Ka emission line
• A large-scale CO survey of the Rosette Molecular Cloud: assessing the effects of O stars on surrounding molecular gas
• Molecular globules in the Veil bubble of Orion. IRAM 30m 12CO, 13CO, and C18O 2-1 expanded maps of Orion A
• A molecular line survey toward the nearby galaxies NGC 1068, NGC 253, and IC 342 at 3 mm with the Nobeyama 45 m radio telescope: The data
• CMZoom II: Catalog of Compact Submillimeter Dust Continuum Sources in the Milky Way's Central Molecular Zone
• Radiative and mechanical feedback into the molecular gas in the Large Magellanic Cloud. II. 30 Doradus
• Structure and kinematics of shocked gas in Sgr B2: further evidence of a cloud-cloud collision from SiO emission maps
• A thorough view of the nuclear region of NGC 253 - Combined Herschel, SOFIA and APEX dataset
• Mass and motion of globulettes in the Rosette Nebula
• Small-scale physical and chemical structure of diffuse and translucent molecular clouds along the line of sight to Sgr B2
• Ionized gas at the edge of the Central Molecular Zone
• [CII] 158$\mu$m and [NII] 205$\mu$m emission from IC 342 - Disentangling the emission from ionized and photo-dissociated regions
• CO Spectral Line Energy Distributions in Galactic Sources: Empirical Interpretation of Extragalactic Observations
• Far-infrared dust properties in the Galaxy and the Magellanic Clouds
• Dust masses, compositions, and luminosities in the nuclear disks and the diffuse circumnuclear medium of Arp220
• Molecular tracers of radiative feedback in Orion (OMC-1). Widespread CH+ (J=1-0), CO (10-9), HCN (6-5), and HCO+ (6-5) emission
• 2 mm GISMO Observations of the Galactic Center. I. Dust Emission
• On the effects of UV photons/X-rays on the chemistry of the Sgr B2 cloud
• High-velocity hot CO emission close to Sgr A*: Herschel/HIFI submillimeter spectral survey toward Sgr A*
• Self-generated ultraviolet radiation in molecular shock waves I. Effects of Lyman $\alpha$, Lyman $\beta$, and two-photon continuum

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• Surveying the Whirlpool at Arcseconds with NOEMA (SWAN)- I. Mapping the HCN and N${}_2$H${}^{+}$ 3mm lines
• SOFIA-upGREAT imaging spectroscopy of the [C II] 158um fine structure line of the Sgr B region in the Galactic center
• Chemical templates of the Central Molecular Zone. Shock and protostellar object signatures under Galactic Center conditions
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