1,437 research outputs found
Current star formation in S0 galaxies: NGC 4710
Elliptical (E) and lenticular (S0) galaxies lack the substantial interstellar medium (ISM) found in the star-forming spiral galaxies. However, significant numbers of E and S0 galaxies are known to contain detectable amounts of interstellar matter (e.g., Jura 1988). Thus, it is worth investigating whether these galaxies are currently able to form stars from their ISM, or whether they should be consigned to the dustbin of inert objects (Thronson and Bally 1987). The results strongly imply that current star formation is responsible for NGC 4710's far infrared and radio continuum properties. If this is indeed the case, then one expects this star formation to be fueled by molecular gas, which is presumably dominated by H2 and can be traced by the CO-12 J=1 to 0 line. Both Kenney and Young (1988) and Sage and Wrobel (1989) have detected such an emission line from NGC 4710, and infer the presence of more than 10(exp 8) solar mass of H2. The origin of the molecular gas in NGC 4710 remains a mystery. The galaxy is very deficient in HI (Kenney and Young, in preparation), suggesting that it originally was a spiral galaxy from which the outer, mainly atomic, gas was stripped by the ram pressure of the Virgo Cluster's intracluster medium, leaving only a central interstellar medium (ISM) rich in molecular gas. Alternatively, the CO may have originated via stellar mass loss with subsequent cooling, cooling flows, or capture from a gas-rich companion. Information on the morphology and kinematics of the CO can be compared with that of the galaxy's other gases and stars to distinguish among these various possible origins for the molecular gas. Major axis CO mapping with single dishes indicate an unresolved source. Thus, a millimeter array is currently being used to image NGC 4710 in CO to provide the needed morphological and kinematical data
Evidence from the Very Long Baseline Array that J1502SE/SW are Double Hotspots, not a Supermassive Binary Black Hole
SDSS J150243.09+111557.3 is a merging system at z = 0.39 that hosts two
confirmed AGN, one unobscured and one dust-obscured, offset by several
kiloparsecs. Deane et al. recently reported evidence from the European VLBI
Network (EVN) that the dust-obscured AGN exhibits two flat-spectrum radio
sources, J1502SE/SW, offset by 26 mas (140 pc), with each source being
energized by its own supermassive black hole (BH). This intriguing
interpretation of a close binary BH was reached after ruling out a
double-hotspot scenario, wherein both hotspots are energized by a single,
central BH, a configuration occuring in the well-studied Compact Symmetric
Objects. When observed with sufficient sensitivity and resolution, an object
with double hotspots should have an edge-brightened structure. We report
evidence from the Very Long Baseline Array (VLBA) for just such a structure in
an image of the obscured AGN with higher sensitivity and resolution than the
EVN images. We thus conclude that a double-hotspot scenario should be
reconsidered as a viable interpretation for J1502SE/SW, and suggest further
VLBA tests of that scenario. A double-hotspot scenario could have broad
implications for feedback in obscured AGNs. We also report a VLBA detection of
high-brightness-temperature emssion from the unobscured AGN that is offset
several kiloparsecs from J1502SE/SW.Comment: 12 pages, 1 figure, accepted by ApJL on 2014 July 2
Recommended from our members
Designing sustainable medical devices
Stakeholders in the medical device manufacturing industry are becoming more concerned about the environmental impact of their products and processes. The consumers are also becoming more aware of the negative impact that manufacturers can have on the environment. Government initiatives continue to increase environmental awareness through the development of new policy and legislation, encouraging industry to become more accountable for the environmental impact of their products and operations. The ISO 14001 standard, Environmental Management Systems-Requirements with Guidance for Use, sets guidelines to enable businesses to recognize the environmental effects of their products and processes. Departments can use the tool to set targets to lower the environmental impact and identify areas of high environmental concern when designing, purchasing, and marketing products. Research in these areas will be used to develop the environmental scoring tool to aid in the design of future sustainable medical devices
- …